Silva , J o sé Ro b ert o La p a e , et al.
O ressu rgim en t o da t u bercu lose e o im pact o do est u do da im u n opat ogen ia pu lm on ar
The resurg ence of tuberculosis and the impact of the
study of pulmonary immunopathog enesis*
JOSÉ ROBERTO LAPA E SILVA*, NEIO BOÉCHAT**
The resurgence of tuberculosis as one of the most important infectious diseases to affect mankind came after the illusion
that the disease was under control and would be eradicated before the end of the 20 th Century. Over the last 10 years,
in association with American and European research centers, our group at the Universidade Federal do Rio de Janeiro
has been dedicated to investigating the pathogenic mechanisms involved in pulmonary tuberculosis. Due to its frequency
and role in transmission, pulmonary tuberculosis is the most serious form of the disease. Our hypothesis is that the
establishment of latent infection and its progression to active disease depend on an imbalance between activating and
deactivating cytokines at the disease site. Despite the presence of protective mechanisms such as the macrophage
expression of phenotypes (denoting cellular and molecular activation of agents involved in protection, such as nitric
oxide and interferon- γ ), tuberculosis progresses. A possible explanation for this is the concomitant presence at the site of
infection of molecules such as interleukin- 10 and TGF- β, which are able to deactivate previously activated macrophages.
Recent data suggest that mycobacteria secrete proteins capable of inducing interleukin- 10, thus contributing to overcoming
host protective mechanisms. Susceptible individuals would be more able to produce larger amounts of these molecules
due to genetic polymorphisms that facilitate interleukin- 10 production at infection onset. The understanding of these
mechanisms could advance the prevention and discovery of new therapeutic targets for the control of tuberculosis.
Key words: Tuberculosis/ethiology. Tuberculosis pulmonary/pathology.
St u d y carried o u t at t h e Un iversid ad e Fed eral d o Rio d e J an eiro (Rio d e J an eiro Fed eral Un iversit y) an d Weill Co rn ell Med ical Co lleg e, Un iversit é
d e Pa ris VI (VI Pa ris Un iversit y)**.
Ad d ress fo r co rresp o n d en ce: Un id a d e d e Pesq u isa em Tu b ercu lo se. Av. Brig ad eiro Tro m p o vski, s/ n . Préd io d o HUCFF/ UFRJ , sa la 01 D5 6 , 1 º a n d a r.
Ilh a d o Fu n d ã o , Rio d e J a n eiro , RJ CEP 2 1 9 41 - 5 9 0 . Tel: 5 5 2 1 2 5 6 2 2 8 8 7 . E- m a il: jrla p a .n t g @ t erra .co m .b r
Fin a n cia l su p p o rt : Re d e Bra sile ira d e Pe sq u isa e m TB (Re d e - TB, Bra z ilia n Tu b e rcu lo sis Re se a rch Ne t wo rk)/ Gra n t n o . 6 2 .0 0 5 5 / 01 - 4 - PACDTMilen io .
Submitted: 1 0 May 2 0 0 4 . Accepted, after review: 2 8 May 2 0 0 4 .
478
Jornal Brasileiro de Pneumologia 3 0 (4 ) - Jul/ Ago de 2 0 0 4
INTRODUCTION
Abbreviatio ns used in this paper:
The phrase “t he resu rgen ce of…” u sed in ou r
t it le is q u it e sig n ifican t if we co n sid er it as a
m arket in g ploy. Those who are fam iliar wit h t he
hist ory of t u bercu losis (TB) in Brazil will recogn ize
it as an u n t ru t h. In act u alit y, TB has n ever ceased
t o be a problem in ou r cou n t ry, or in t hird- world
cou n t ries in gen eral. What did chan ge was t he
prevalen ce of TB in developed cou n t ries. It was
believed t hat TB had been virt u ally eradicat ed in
t h e so - ca lled first - wo rld co u n t ries. Pro m in en t
a u t h o rs st a t ed t h a t TB wa s b ein g era d ica t ed
worldwide, just as sm allpox had been . However,
t hey were act u ally referrin g t o t he eradicat ion of
TB in first - wo rld co u n t ries. In t h e 1 9 7 0 s, t h e
prevalen ce rat es of TB in Hollan d were ext rem ely
low an d were fallin g even lower. The sam e was
t ru e in t he rest of Eu rope an d in t he Un it ed St at es.
In ot her words, first - world cou n t ries were act u ally
m akin g progress in t he eradicat ion of TB. What
has chan ged? What has m ade TB a disease t hat is
n o lon ger con sidered eradicable, at least in t he
begin n in g of t his n ew cen t u ry? The year 1985
represen t s t he m om en t at which TB in dices began
t o rise on ce again . This is at t ribu t able t o a n u mber
of fact ors, on e of which is in creased m igrat ion .
Reservoirs of TB exist in Africa, Sou t h America an d
Cen t ral America. Asia is on e of t he great reservoirs
of TB in t he world, rivaled on ly by In dia in t he
st at ist ics. Con siderin g t hat in t ern at ion al migrat ion
co n t in u e s t o in cre a se , e sp e cia lly fro m t h e se
reservoir areas t o developed cou n t ries, it is obviou s
t hat t hese reservoirs will even t u ally be replicat ed
in f irst - w o rld co u n t rie s, d e sp it e TB co n t ro l
program s in t hose developed cou n t ries t hat open
t heir doors t o immigrat ion .
Nevert heless, t here is on e hist orical fact or t hat
can be held respon sible for t he chan ges in t he TB
prevalen ce cu rve: t he acqu ired im m u n odeficien cy
syn drom e (AIDS) pan dem ic, which in t rodu ced a
n ew realit y, sin ce in dividu als in fect ed wit h TB who
also becom e in fect ed wit h t he AIDS viru s rapidly
con vert t o act ive TB. Addit ion ally, TB does n ot
re q u ire a ve ct o r f o r it s t ra n sm issio n , b e in g
t ra n sm it t ed fro m p erso n - t o - p erso n . A h u m a n
immu n odeficien cy viru s- posit ive (HIV+) in dividu al
is at greater risk for developing TB. When the active
form of t he disease is at t ain ed, t he bacillu s m ay
be t ran sm it t ed t o in dividu als who are n ot HIV+,
su ch as healt h profession als, prison m at es an d
AIDS
HIV
HLA- DR
Mt b
NOS2
TB
TGF
–
–
–
–
–
–
–
Acq u ired im m u n o d eficien cy syn d ro m e
Hu m a n im m u n o d eficien cy viru s
Hu m a n leu ko cyt e a n t ig en - D reg io n
Myco b a ct eriu m t u b ercu lo sis
In d u cib le n it ric o xid e syn t h a se
Tu b ercu lo sis
Tu m o r g ro wt h fa ct o r
sh elt er m at es. Th erefo re, t h e p revalen ce o f TB
in creases expon en t ially, resu lt in g from a sit u at ion
t hat is n ot direct ly or n ecessarily relat ed t o t he
AIDS viru s. This is why TB has again been in t he
headlin es an d is con sidered to be on the rise, which
led t he World Healt h Organ izat ion t o declare TB a
global healt h em ergen cy in 1995.
We m u st bear in m in d t hat we are referrin g t o
a disease t hat has afflict ed hu m an kin d for ages.
We kn ow t hat TB has been fou n d in mat erial t aken
from 4000- year- old Egypt ian m u m m ies, in which
it w a s id e n t if ie d u s in g m o le c u la r b io lo g y
t echn iqu es t hat em ploy kn own sequ en ces of t he
gen ome of t hese mycobact eria. Eviden ce of TB has
also been fou n d in t he bon es of Neolit hic hu man s.
In the Middle Ages, it was called the “white plague”.
There is a ren ewed in t erest in TB exhibit ed by t he
m edia, which cou ld resu lt in addit ion al fu n din g
for research. In fact , lack of fin an cial su pport for
r e s e a r c h is t h e p r im a r y r e a s o n t h a t o u r
u n derst an din g of TB has n ot kept pace wit h t he
advan ce of t he disease. Therefore, we view TB as
it was in t he last cen t u ry. In clin ical pract ice, we
st ill u se t echn iqu es t hat have been u sed for u p t o
100 years. Man y of ou r diagn ost ic m et hods, su ch
a s p u rif ie d p ro t e in d e riva t ive t e st in g , w e re
developed 100 years ago. Our therapeutic regimens,
in clu d in g an t i- TB d ru g s su ch as iso n iazid an d
st rept om ycin , were developed 50 years ago. In
addit ion , t he vaccin es cu rren t ly in u se, su ch as
t he bacillu s Calm et t e- Gu érin vaccin e (which was
developed in 1909) are qu it e dat ed. In vest men t in
TB resea rch p a les in co m p a riso n t o t h e so lid
fin an cial su pport provided for research in t o ot her
diseases su ch as AIDS.
Tu b ercu lo sis h as always b een a p ro b lem in
Brazil, alt hou gh t he hist orical an d cu rren t lack of
fu n d in g fo r TB resea rch h a s p erp et u a t ed t h is
problem. In first- world countries, which traditionally
in vest heavily in research in t he broader areas of
479
Silva , J o sé Ro b ert o La p a e , et al.
O ressu rgim en t o da t u bercu lose e o im pact o do est u do da im u n opat ogen ia pu lm on ar
Biology an d Biom edicin e, TB has effect ively been
left behin d. This is a disease t hat will kill 30 million
people worldwide over t he n ext t en years. There
are few com parable sit u at ion s. When we con sider
t he level of fin an cial su pport for TB research an d
TB- co n t ro l p ro g ra m s wo rld wid e , it b e co m e s
obviou s t hat t he su m in vest ed is t ot ally in adequ at e
an d disproport ion at e. Priorit y shou ld be given t o
TB, althou gh, u n fortu n ately, there are precious few
who t hin k so.
Even prior to the introduction of chemotherapy,
e p id e m io lo g ica l in d ice s o f TB w e re f a llin g ,
especially in first- world countries. At the beginning
of t he 20t h cen t u ry, t here was a high prevalen ce
o f TB in t h e Un it ed St a t es, wh ere p ro g ressive
im provem en t in qu alit y of life even t u ally brou ght
abou t a sign ifican t redu ct ion in all epidemiological
indicators, even prior to the introduction of specific
chem ot herapy. The in t rodu ct ion of st rept om ycin ,
the first effective anti- TB drug, resulted in a second
con siderable redu ct ion in TB in dices, which was
repeated years later, when isoniazid was introduced.
Th e u n d e r s t a n d in g o f t h e p o s t u la t io n s o f
c h e m o t h e ra p y d a t e s f ro m t h e sa m e p e rio d ,
in dicat in g t hat t he u se of t hese dru gs shou ld be
u se d in c o m b in a t io n in o rd e r t o a vo id t h e
appearance of resistant strains. From the beginning
of t he 1950s t o t he begin n in g of t he 1980s, t here
was an en ormou s redu ct ion in t he in ciden ce of TB
in t h e USA, in Eu ro p e a n d in t h e rest o f t h e
developed world. However, TB in ciden ce was also
redu ced sign ifican t ly in poor cou n t ries su ch as
Brazil an d In dia. This was du e t o an overall global
im p ro ve m e n t in s a n it a t io n , e ve n in p o o re r
cou n t ries. Gen eral developm en t , especially in t he
areas of t echn ology, scien ce an d san it at ion over
t he cou rse of t he cen t u ry facilit at ed t he con t rol of
all diseases. This phen om en on is n ot rest rict ed t o
TB alon e, alt hou gh it s con t rol also ben efit ed from
the general improvement in quality of life. However,
midway t hrou gh t he 1980s, t here was an in flect ion
in t h e TB p re va le n ce cu rve , re su lt in g in a n
ascen dan t t en den cy, which st ill prevails.
The pathogeny of tuberculosis
The immu n opathogen y of TB, or rather the way
t h e h o st im m u n e syst e m a ct s t o im p e d e t h e
p ro g ress o f t h e d isea se, is a su b ject t h a t h a s
su ffered sign ifican t ly from t he lack of in vest m en t
in research. Amon g the TB- related facts men tion ed
480
above, on e in part icu lar calls at t en t ion t o t he n eed
for research in t his area: TB has in fect ed on e- t hird
o f t h e g lo b a l p o p u la t io n , in wh ich t h ere a re
a p p ro xim a t ely 1 0 m illio n ca ses o f a ct ive- TB.
Becau se t hey possess defen se m echan ism s t hat
keep t he mycobact eria in check, t hereby impedin g
it s act ivit y, t he rem ain in g in fect ed in dividu als do
n ot develop t he disease. Obviously, if we can gain
a re a so n a b le u n d e rst a n d in g o f t h is d e f e n se
m echan ism , we will able t o com prehen d t he ot her
sid e o f t h e eq u a t io n : wh a t ca u ses 5 % o f a ll
con t am in at ed in dividu als t o develop t he disease.
In fect io n wit h Myco b a ct eriu m t u b ercu lo sis
(Mt b) has t hree possible ou t com es: resolu t ion at
t he poin t of en t ry (du e t o in n at e immu n it y), act ive
disease or lat en t TB. In t he last case, t he organ ism
con t rols, bu t does n ot elimin at e, t he in fect ion . The
Mt b rem ain s dorm an t , replicat in g in t erm it t en t ly
an d presen t in g an alt ered met abolism. This creat es
a m assive reservoir of TB. Several qu est ion s are
relevan t t o t his problem . Which in it ial even t s lead
t o im m ed ia t e co n t ro l o f t h e in fect io n ? Wh ich
fact ors con t ribu t e t o t he on set of lat en t in fect ion ?
By iden t ifyin g t he m echan ism s in volved, we can
p r o p o s e va c c in a t io n s , c h e m o t h e r a p ie s a n d
a d ju va n t im m u n o t h e ra p ie s t h a t m a y p re ve n t
pat ien t s from developin g t he act ive form of TB.
Im m u n o lo g y e f f e c t ive ly b e g a n w it h t h e
discoveries m ade by Robert Koch in t he 1890s.
However, it may be considered a very recent science,
sin ce t he T lymphocyt e an d t he B lymphocyt e were
n ot iden t ified u n t il t he begin n in g of t he 1970s.
Even t hen , we kn ew n ot hin g abou t cyt okin es, t he
u n d erst a n d in g o f wh ich h a s b ro u g h t a b o u t a
revolu t ion in t he field of biology.
Th e o rg a n ism d e f e n d s it se lf a g a in st t h e
m ycobact eria wit h t he aid of t wo cell t ypes: t he T
lym p h o cyt e a n d t h e m a cro p h a g e . Wh e n t h e
m ycobact eria in vade t he lu n g of t he su bject aft er
havin g been expect orat ed in m icropart icles by a
t u bercu lou s pat ien t , it is in it ially phagocyt osed by
an alveolar m acrophage at t he first close con t act
wit h t he lu n g. Depen din g on t he viru len ce of t he
bacillu s an d t he qu an t it y in haled, t his macrophage
m ay or m ay n ot resolve t he problem t here, at t he
poin t of en t ry. However, t he m acrophage is rarely
capable of dest royin g t he m ycobact eria alon e. It
n eeds t he assist an ce of ot her cells, especially in
the form of cytokine production, which will enhance
t h e a b ilit y o f t h e m a c r o p h a g e t o k ill t h e
Jornal Brasileiro de Pneumologia 3 0 (4 ) - Jul/ Ago de 2 0 0 4
mycobacteria within its own cytoplasm. In addition
t o produ cin g import an t cyt okin es, T lymphocyt es,
in t heir effect or role, represen t a powerfu l weapon ,
sin ce t hey are able t o dest roy m acrophages t hat
have su ccu m bed t o t he m ycobact eria. On ce t he T
lym phocyt e recogn izes t hat t he m acrophage has
lost t his bat t le, it kills t he m acrophage, releasin g
t he bacillu s in t o t he en viron m en t , where m ore
e ffe ct ive m a cro p h a g e s ca n p h a g o cyt o se a n d
con t rol it . This represen t s an effect or act ion of
the T lymphocyte itself against mycobacteria, albeit
in an in direct way.
We h a ve b e g u n t o re co g n iz e ce rt a in ce ll
su bpopu lat ion s, su ch as t he T γ δ lym phocyt es,
which play a very im port an t role in com bat in g TB
since they are highly toxic to infected macrophages
and produce cytokines that stimulate the remaining
m acrophages t o kill t he m ycobact eria. Even t he
m acrophage is n o lon ger sim ply con sidered an
effect or cell, bu t also on e of t he m ost im port an t
in du cers of cyt okin e produ ct ion . In light of t his
n ew kn owledge, we moved away from t he con cept
t h at in d u ct io n o f t h e im m u n e resp o n se wo u ld
always be carried ou t by T lym phocyt es an d t hat
t he effect or act ion wou ld always be provided by
t h e m a c ro p h a g e . We n o w kn o w t h a t t h e T
lymphocyte and the macrophage may play the roles
of bot h in du ct ors an d effect ors.
An ot her reason for reevalu at in g ou r previou s
con cept ion of TB is t he adven t of HIV. The AIDS
pan demic has imposed on hu man kin d a revolu t ion
in t he field on immu n ology. Never before has t here
been progress su ch as t hat seen in t he last 20
years. An HIV+ pat ien t presen t s a form of TB t hat
is ve r y d if f e r e n t f r o m t h a t s e e n in
im m u n ocom pet en t in dividu als: it is m u ch m ore
severe, m ore oft en fat al an d has a m u ch worse
effect on t he su rvival of t he pat ien t . In dividu als
die m ore rapidly when su fferin g from TB an d HIV
co n co m it a n t ly. Even if t h e TB is cu red , AIDS
su rvival t im e is redu ced (1 ).
The role of cytokines in the development
of tuberculosis
It is essential to understand the mycobactericidal
mechan isms of macrophages an d how t he immu n e
syst em, especially t he pu lmon ary immu n e syst em,
part icipat es in t hese mechan isms. In virt u ally all
cases, TB t ran smission occu rs via t he airways, an d
80% presen t as t he pu lmon ary form of t he disease.
In addit ion , t he pu lmon ary form is t he on ly form
t hat is epidemiologically sign ifican t , sin ce it allows
person- to- person transmission, thereby maintaining
t h e d isea se t ra n sm issio n cycle. Cyt o kin es a re
hormon es t hat are t he produ ct s of several t ypes of
cells wit hin t he organ ism an d have a variet y of
fu n ct ions. In t he case of TB, specifically, t hey play
very import an t roles, which we are on ly begin n in g
t o u n derst an d.
We u n derst an d t hat , t o be prot ect ed again st
TB, an in dividu al n eeds t o possess a part icu lar t ype
of cyt okin e t hat en ables m acrophages t o kill t he
m ycobact eria. However, we are also begin n in g t o
understand that there are certain types of cytokines
t hat , in versely, deact ivat e m acrophages, t hereby
preven t in g t he dest ru ct ion of t he m ycobact eria.
There are cyt okin es of bot h Th1 an d Th2 profiles.
In short , t he Th1 cyt okin es are t hose, su ch as IFNγ a n d IL- 2 , wh ich a ct iva t e t h e m a cro p h a g e
microbicidal mechan isms, an d Th2 cyt okin es, su ch
as IL- 4, IL- 5 and IL- 10, deactivate the macrophage.
Depen din g on t he prevalen ce of t hese t ypes of
cyt okin es, TB will progress or will be preven t ed.
Ou r hypot hesis is t hat t here is a prevalen ce of
deact ivat in g cyt okin es when t he disease develops,
even when act ivat in g cyt okin es are presen t . If t he
in fect ed in d ivid u a l h a s a g en et ic t en d en cy t o
produ ce a great er am ou n t of IL- 10, for exam ple,
h is ch a n ces o f d evelo p in g TB will b e h ig h er.
Therefore, gen et ic polymorphisms, which facilit at e
a g reat er p ro d u ct io n o f IL- 1 0 wh en facin g an
in fect iou s disease, wit hin cert ain popu lat ion s may
be u sed in t he fu t u re as gen et ic m arkers for t he
st u d y o f g ro u p s wit h h ig h er o r lo wer risk o f
developin g act ive TB. There are ways t o iden t ify
popu lation grou ps which are high or low produ cers
o f IL- 1 0 . If a n in d ivid u a l co n t a m in a t e d b y
m ycobact eria is a m ajor produ cer of IL- 10, he will
be t reat ed wit h great er care, an d will probably be
requ ired t o t ake an IL- 10 in hibit or.
As yet u n pu blished st u dies t hat were recen t ly
co n d u ct ed by o u r g ro u p , led by Dr. Ad a lb ert o
Rezen d e, h ave sh o wn a st at ist ically sig n ifican t
correlat ion bet ween cert ain haplot ypes t hat are
facilit at ors of IL- 10 produ ct ion an d higher rat es of
act ive TB. In an experimen t al st u dy in mice t hat
have been gen et ically alt ered in order t o presen t
exaggerat ed expression of IL- 10, it was shown t hat
n ormally su blet hal doses of mycobact eria are fat al
fo r t h e se a n im a ls (2 ). In co n t ra st , t h e a u t h o rs
481
Silva , J o sé Ro b ert o La p a e , et al.
O ressu rgim en t o da t u bercu lose e o im pact o do est u do da im u n opat ogen ia pu lm on ar
demon st rat ed t hat wild- t ype mice, t hat produ ce a
lower amount of IL- 10, survive the same dose levels,
sh o win g t h at exag g erat ed p ro d u ct io n o f IL- 1 0
redu ces t he chan ce of su rvivin g a mycobact erial
infection.
Ou r grou p at t he Un iversidade Federal do Rio
de J an eiro (Rio de J an eiro Federal Un iversit y) has
worked in con ju n ct ion wit h Corn ell Un iversit y in
New York for t he last t en years, developin g an d
pu blishin g variou s stu dies that focu s on evalu atin g
cells collect ed from TB- affect ed areas of t he lu n gs.
Ou r aim has been t o det erm in e whet her t here is
en han ced or redu ced expression of IL- 10 or ot her
cyt okin es wit h sim ilar act ion s t hat cou ld gen erat e
t h is im m u n o lo g ica l d ysfu n ct io n . Ou r st u d ie s
in clu ded pat ien t s wit h pu lmon ary TB su bmit t ed t o
diagn ost ic bron choalveolar lavage becau se t hey
were n ot produ cin g spu t u m or produ ced spu t u m
t h a t t e st e d n e g a t ive f o r m yc o b a c t e ria . Th e
t echn iqu e in volves drawin g an d cen t rifu gin g t he
flu id, aft er which t he su pern at an t is st ored an d
t he cells are st u died. In order t o det ermin e whet her
t h e r e is e xa g g e r a t e d e xp r e s s io n o f c e r t a in
cyt okin es, t he whole cell m ay be st u died in t he
cyt o ce n t rifu g e d m a t e ria l, o r t h e ce ll ca n b e
flattened and the genetic material extracted. In one
o f t h e e a r ly s t u d ie s (3 ) , w e d e t e r m in e d t h e
phen otype of the T lymphocytes an d macrophages,
an d we fou n d t hat TB pat ien t s wit h con com it an t
HIV a ls o p re s e n t e d d ys f u n c t io n w it h in t h e
m acrophage popu lat ion . In gen eral, we believe
t hat , in HIV in fect ion , t here are basic defect s in
t he T CD4+ lym phocyt e, whereas, in pat ien t s wit h
TB an d HIV, t he macrophage it self becomes u n able
t o gen erat e a defen se again st t he m ycobact eria.
Epit helioid cells iden t ified by specific m on oclon al
a n t ib o d y a re p re se n t in sig n ifica n t ly g re a t e r
n u m bers in t he bron choalveolar lavage flu id of
immunocompetent patients, whereas their numbers
are redu ced in HIV+ pat ien t s. We also st u died t he
macrophage expression of cert ain molecu les, su ch
as t he hu m an leu kocyt e an t igen - D region (HLADR), which is a T lym phocyt e an t igen - presen t in g
c e ll. Wh e n t h is m o le c u le is f o u n d in g re a t
q u a n t it ie s, it re su lt s in e n h a n c e d a n t ig e n p resen t in g abilit y. In TB pat ien t s, t he qu an t it y of
HLA- DR is mu ch great er t han in con t rols, whereas
in TB patients with concomitant HIV it is very much
d im in ish ed , d em o n st rat in g a d efect wit h in t h e
m acrophage it self.
482
We also st u died n it ric oxide, which is an ot her
m olecu le t hat is very im port an t in t he defen se
again st mycobacteria, an d the n itric oxide in du ctor
en zym e, a lso kn o wn a s in d u cib le n it ric o xid e
syn t h a se (NOS2 ). We d em o n st ra t ed in crea sed
en zym e exp ressio n (4 ) wit h in t h e p o p u la t io n o f
pat ien t s wit h TB. Therefore, alt hou gh we have
demon st rat ed t hat t here is an in crease of HLA- DR,
as well as an in crease in t he NOS2 en zym e (bot h
o f wh ich sh o u ld , t h e o re t ica lly, p ro t e ct t h e se
in dividu als), t hey con t in u e t o be ill. We believe
t his is becau se, even in t he presen ce of in creased
expression of t hese defen se fact ors, som et hin g is
im pedin g t he prot ect ion . We hypot hesize t hat t he
d ea ct iva t in g cyt o kin es a re resp o n sib le fo r t h is
hin dran ce. In a su bsequ en t st u dy, we assessed t he
q u a n t it y o f c yt o k in e s p r e s e n t in t h e
bron choalveolar lavage flu id of TB pat ien t s (5 ). We
determined that levels of the cytokine that activates
macrophage microbicidal fu n ct ion , n amely IFN- γ ,
are in creased, as we wan t t hem t o be. However,
t he pat ien t presen t s act ive TB an d will die if n ot
t reat ed, dem on st rat in g t hat IFN- γ alon e has n o
effect . This is probably du e t o t he fact t hat , wit hin
t h e sa m e m a t e ria l, t h e re is co e xp re ssio n o f
deactivatin g cytokin es, which perform a sign ifican t
physiological fu n ct ion in con t ain in g t he im m u n e
react ion s aft er t he st im u lu s for t hat react ion has
b een wit h d ra wn . Th ese a re a n t i- in fla m m a t o ry
cyt okin es, which are import an t in in t erru pt in g t he
in flam m at ory process. The problem is t hat t heir
expression is apparen t ly in creased when it shou ld
n ot be. Recen t st u dies con du ct ed by ou r grou p
have shown t his coexpression of act ivat in g an d
d e a ct iva t in g cyt o kin e s. Fu rt h e rm o re , a n o t h e r
d ea ct iva t in g cyt o kin e kn o wn a s t u m o r g ro wt h
factor- β (TGF- β ) is also increased. In patients with
TB, we have dem on st rat ed t hat , in addit ion t o
in creased expression of t his cyt okin e, n u m bers of
t he cellu lar recept ors requ ired for TGF- β act ivit y
are also in creased (6 ).
Th is im b a la n ce a id s t h e est a b lish m en t a n d
progress of t he in fect ion . As previou sly men t ion ed,
t here are gen et ic alt erat ion s t hat cou ld facilit at e
t he exaggerat ed produ ct ion of cyt okin es su ch as
IL- 10 at a momen t when t heir presen ce at t he sit e
o f in fect io n m a y ca u se t h e im m u n e p ro t ect o r
respon se t o become complet ely u n balan ced. There
is in creasin g eviden ce t hat , in it s growt h phase,
Mt b it self secret es som e prot ein s t hat are capable
Jornal Brasileiro de Pneumologia 3 0 (4 ) - Jul/ Ago de 2 0 0 4
o f sig n ifica n t ly in t e rfe rin g wit h t h e im m u n e
resp o n se – wo rkin g in it s fa vo r, so t o sp ea k.
Recently published studies conducted by our group
at t he Un iversit y of Corn ell show t hat on e of t hese
prot ein s, kn own as CFP32, is expressed on ly by
members of t he Mt b complex an d is n ot expressed
by ot her species of m ycobact eria. In vit ro an d ex
vivo st u dies have shown t hat t his prot ein is able
t o in du ce con siderable produ ct ion of IL- 10, which,
as previou sly m en t ion ed, facilit at es t he progress
of t he in fect ion (7 ). The presen ce of t his gen e in
t he m ycobact eria has advan ced t he developm en t
of n ew diagn ost ic m et hods as well as aidin g t he
iden t ificat ion of su bspecies wit hin t he gen u s, wit h
im plicat ion s for st u dies t hat focu s on m olecu lar
epidem iology(8 ).
Role of dendritic cells
An ot her cell t ype t hat merit s fu rt her st u dy, du e
t o it s abilit y t o in du ce a pot en t ially lon g- last in g
prot ect ive immu n e respon se t o TB, is t he den drit ic
ce ll. Su fficie n t n u m b e rs o f t h is t yp e o f ce ll,
t oget her wit h ot her t ypes of cells of t he mon ocyt em acrophage lin eage, are essen t ial for gran u lom a
format ion , which simu lt an eou sly prot ect s t he host
from dissem in at ion of t he in fect ion an d prot ect s
the microorganism from being eliminated (9). A dense
cellu lar popu lat ion an d t he presen ce of cert ain
cyt okin es, su ch as t ype- I in t erferon , are essen t ial
for gran u lom a form at ion an d redu ct ion of t he
bact erial load (1 0 ). Recen t st u dies con du ct ed by ou r
grou p, in associat ion wit h researchers from t he
In st it u t Past eu r de Paris (Paris Past eu r In st it u t e)
have shown t he im port an ce of t hese m echan ism s
in est ablishin g a prot ect ive response t o TB(11 ,1 2 ).
In con clu sion , t he st u dy of t he m echan ism s
t hrou gh which t he host defen ds it self again st Mt b
in fect ion , as well as of t he pot en t ial m echan ism s
by which t he m ycobact eria m an ipu lat es t he host
im m u n e syst em in it s own favor, m ay shed n ew
light on t he pat hogen y of TB. The resu lt of t his
wou ld be bet t er vaccin es, n ew t herapeu t ic t arget s
a n d m o r e p r e c is e d ia g n o s t ic m e t h o d s f o r
com bat in g t his t errible illn ess.
REFERENCES
1 . Krit ski AL, La p a e Silva J R, Co n d e MB. Tu b ercu lo sis
a n d HIV: ren ewed ch a llen g e. Mem . In st . Oswa ld o Cru z
1 9 9 8 ; 9 3 : 41 7 - 2 1 .
2 . Murray PJ, Wang L, Onufryk C, Tepper RI, Young RA. T celld e rive d IL- 1 0 a n t a g o n iz e s m a cro p h a g e f u n ct io n in
mycobact erial in fect ion . J. Immu n ol. 1997;158:315- 21.
3 . Lap a e Silva J R, Lin h ares C, Bo ech at N, Reg o L, Bo n ecin i
Alm e id a MG, Krit ski AL, e t a l. P h e n o t yp e s o f lu n g
m o n o n u clear p h ag o cyt es in t h e b ro n ch o alveo lar lavag e
f lu id o f HIV s e r o n e g a t ive t u b e r c u lo s is p a t ie n t s :
evid en ce fo r n ew recru it m en t an d cell act ivat io n . Mem .
In st . Oswa ld o Cru z 1 9 9 6 ; 91 :3 8 9 - 9 4 .
4 . Nich o lso n S, Bo n ecin i- Alm eid a MG, La p a e Silva J R,
Na t h a n C, Xie QW, Mu m f o rd R, We id n e r J R, e t a l.
In d u cib le n it ric o xid e syn t h a se in p u lm o n a ry a lveo la r
m a cro p h a g es fro m p a t ien t s wit h t u b ercu lo sis. J . Exp .
Me d . 1 9 9 6 ; 1 8 3 : 2 2 9 3 - 3 0 2 .
5 . Bo n e cin i- Alm e id a MG, La p a e Silva J R, Krit ski AL,
Mo rg ad o MG, Nat h an C, Ho J L Im m u n e resp o n se d u rin g
HIV an d t u b ercu lo sis co - in fect io n . Mem . In st . Oswald o
Cru z 1 9 9 8 ; 9 3 :3 9 9 - 4 0 2 .
6 . Bon ecin i Almeida MG, Ho JL, Boéchat N, Hu ard RC, Chitale
S, Do o H, et a l. Do wn - Mo d u la t io n o f Lu n g Im m u n e
Respon ses by In t erleu kin - 10 an d Tran sform in g Growt h
Factor- β (TGF- β ) and Analysis of TGF- β Receptors I and II
in Active Tuberculosis. Infect Immun 2004; 72:2628- 34.
7 . Hu ard RC, Ch it ale S, Leu n g M, Lazzarin i LCO, Zh u H,
Sh a sh kim a E, e t a l. Th e Myco b a ct eriu m t u b ercu lo sis
co m p le x- re st rict e d g e n e cp f3 2 (Rv0 5 7 7 ) e n co d e s a n
e x p r e s s e d p r o t e in t h a t is d e t e c t a b le in h u m a n
t u bercu losis pat ien t s. In f. Immu n . 2003; 71:6871- 6883.
8 . Hu ard RC, Lazzarin i LCO, Bu tler WR, van Sooligen D, Ho
JL. A PCR- base method to differentiate the subspecies of
the Mycobacterium tuberculosis complex on the basis of
gen omic delet ion . J Clin Microb. 2003; 41:1637- 50.
9 . Boechat N, Bou chon n et F, Bon ay M, Grodet A, Pelicic V,
Gicqu el B, et al. Cu lt u re at high den sit y im proves t he
abilit y of hu man macrophages t o con t rol mycobact erial
gro wt h . J . Im m u n o l. 2 0 01 ; 1 6 6 :6 2 0 3 - 11 .
1 0 . Bo u ch o n n et F, Bo ech at N, Bo n ay M, Han ce AJ . Alp h a/
b e t a in t e rf e ro n im p a irs t h e a b ilit y o f h u m a n
m a cro p h a g e s t o co n t ro l g ro w t h o f Myco b a ct e riu m
b o vis BCG. In fect Im m u n 2 0 0 2 ; 7 0 :3 0 2 0 - 5 .
11 . Nah o ri M- A, Lag ran d erie M, Lefo rt J , Th o u ro n F, J o sep h
D, Win t e r N, e t a l. Effe ct s o f Myco b a ct e riu m b o vis
BCG o n t h e d evelo p m en t o f allerg ic in flam m at io n an d
b ro n ch ia l h yp erresp o n siven ess in h yp er- Ig E BP2 m ice
va ccin a t ed a s n ewb o rn s. Va ccin e 2 0 01 ; 1 9 :1 4 8 4 - 9 5 .
1 2 . Lag ran d erie M, Nah o ri MA, Balazu c AM, Kiefer- Biasizzo
H, La p a e Silva J R, Milo n G, e t a l. De n d rit ic ce lls
recru it ed t o t h e lu n g sh o rt ly a ft er in t ra n a sa l d elivery
o f Mycobact eriu m bovis BCG d rive t h e p rim ary im m u n e
re sp o n se t o w a rd s a Th 1 - t yp e cyt o kin e p ro d u ct io n .
Im m u n o lo g y 2 0 0 3 : 1 0 8 : 3 5 2 - 6 4 .
483
