Spleen

Most cytotoxic drugs have gross effects on the immune system, such as neutropenia and lymphopenia. However, their effects on tumor-specific immune responses are unknown. Gemcitabine is a nucleoside analogue that is frequently used to treat non-small cell lung cancer. It is also active in other malignancies, either alone or in combination with cisplatin. Here, we investigate its effects on antigen-specific antitumor immunity using a murine tumor cell line transfected to express influenza virus hemagglutinin (HA). CD4(+), CD8(+), and B220(+) lymphocyte numbers all decreased during chemotherapy (120 microg/g, i.p., every third day for five doses), but B cells were selectively depleted. Gemcitabine induced a profound suppression of the IgG antibody response to HA, and this was unrelated to tumor size. In contrast, in vitro T-lymphocyte recall responses to the class I- and class II-restricted dominant peptide epitopes of HA were enhanced in tumor-bearing, gemcitabine-treated mice. We fou...

The antiviral drug acyclovir [9-(2-hydroxyethoxymethyl)guanine (ACV)], its 7-isomer (7-ACV) and its two derivatives: N2-acetyl ACV (ac-ACV) and N2,O-diacetyl ACV (diac-ACV) were examined for their potential in vitro lymphotoxicity and in vivo immunotoxicity in mice. In vitro lymphotoxicity of ACV and its acetylated derivatives was low, whereas the 7-ACV isomer enhanced the in vitro cell proliferation in PHA-stimulated cultures. Addition of 2'-deoxyguanosine (dGuo) did not exhibit any inhibitory potential of ACV. However, reduction in the absolute number of CD3+, CD8+, and CD25+ cells, but not Ig+ cells, was noted at high concentrations of ACV and its derivatives, suggesting a selective T cell cytotoxicity. Similarly, the in vivo exposure revealed selective T cell immunotoxicity of ACV and its derivatives since the reduced number of Thy 1.2+ and CD8+ cells was not accompanied with any marked changes in the Ig+ population. The CD4+/CD8+ ratio was affected both in vitro and in vivo by high concentrations of ACV.

Treatment of mice with hydroxyurea to selectively kill all cycling cells has been used to study population dynamics and life expectancy of “natural” immunoglobulin-secreting cells in the bone marrow and spleen of nonimmunized animals. The results show that 50 to 90% of those cells are eliminated 2 to 3 days after one cycle of hydroxyurea administration, demonstrating their recent origin from cycling precursors. Using a protocol of long-term hydroxyurea treatment which abrogates cell production from the cycling precursors compartments, it was shown that “natural” immunoglobulin-secreting cells have a very short half renewal time, in the range of 15–60 h.

Microgravity and its environment have adverse effects on the immune system. Abnormal immune responses observed in microgravity may pose serious consequences, especially for the recent directions of NASA for long-term space missions to Moon, Mars and deep Space exploration. The study of space flight immunology is limited due to relative inaccessibility, difficulty of performing experiments in space, and inadequate provisions in this area in the United States and Russian space programs (Taylor 1993). Microgravity and stress experienced during space flights results in immune system aberration (Taylor 1993). In ground-based mouse models for some of the microgravity effects on the human body, hindlimb unloading (HU) has been reported to cause abnormal cell proliferation and cytokine production (Armstrong et al., 1993, Chapes et al. 1993). In this report, we document that a nutritional nucleotide supplementation as studied in ground-based microgravity analogs, has potential to serve as a ...

Objective: Vivax malaria is common in Pakistan. We carried out this study to determine the effects of this infection on blood counts and the impact of splenomegaly on these results.
Methods: This was a retrospective observational study carried out at 1 Mountain Medical Battalion, Bagh, Azad Kashmir. Old medical records of all patients admitted with vivax malaria from Jan 2010 to Oct 2012 were scrutinized. The presence or absence of a palpable spleen and the results of complete blood counts and platelet counts measured at the time of admission were noted down. Anaemia was defined as Hb<13g/dl in men, leukopenia as total leukocyte count (TLC)<4000/µl and thrombocytopenia as platelets count <150000/µl. Data was analysed with STATA version 12.1. The results of haematology parameters were compared amongst patients with splenomegaly and the rest.
Results: Anaemia was seen in 22.15%, neutropenia in 23.49% and thrombocytopenia in 90.60% of the 149 male patients having a mean age of 27.54±5.11 years. The differences in mean blood counts and the number of patients with haematological abnormalities in the two groups were statistically insignificant.
Conclusion: Since the blood counts are not affected by presence or absence of splenomegaly, mechanisms other than hypersplenism are important.

Clinical manifestations of Plasmodium falciparum infection are induced by the asexual stages of the parasite that develop inside red blood cells (RBCs). Because splenic microcirculatory beds filter out altered RBCs, the spleen can innately clear subpopulations of infected or uninfected RBC modified during falciparum malaria. The spleen appears more protective against severe manifestations of malaria in naïve than in immune subjects. The spleen-specific pitting function accounts for a large fraction of parasite clearance in artemisinin-treated patients. RBC loss contributes to malarial anemia, a clinical form associated with subacute progression, frequent splenomegaly, and relatively low parasitemia. Stringent splenic clearance of ring-infected RBCs and uninfected, but parasite-altered, RBCs, may altogether exacerbate anemia and reduce the risks of severe complications associated with high parasite loads, such as cerebral malaria. The age of the patient directly influences the risk o...

Abstract: There is strong evidence that non-immune chronic idiopathic neutropenia of adult is a cytokine-mediated syndrome characterized by (a) neutropenia of varying degree associated with a low number of lineage-specific CD34+ cells and increased production of inhibitors of hematopoiesis, including transforming growth factor-β1 and tumor necrosis factor-α; (b) lymphopenia due to selective loss of primed/memory T-cells and NK cells; (c) increased splenic volume on ultrasonography in 48.1% of patients; (d) osteopenia and/or osteoporosis in 60.0% of patients; (e) anemia, mostly of the type of anemia of chronic disease, in 15.6% of patients; (f) features of chronic antigenic stimulation, including increased proportion of bone marrow plasma cells, increased serum levels of IgG1 and/or IgA, increased frequency of monoclonal gammopathy of undetermined significance, increased frequency of antinuclear antibodies with specific reactivity, and increased serum levels of circulating immune complexes; and (g) increased concentrations of a variety of macrophage-derived pro-inflammatory cytokines and chemokines capable of affecting bone metabolism, bone marrow function, and leukocyte trafficking. All these findings are suggestive of the existence of an unrecognized low-grade chronic inflammatory process which may be involved in the pathogenesis of the disorder. Neutropenia in these patients is probably the result of a combination of at least three factors, reduced neutrophil production in bone marrow, enhanced neutrophil extravasation, and increased sequestration and/or extravasation of neutrophils into the spleen.