Journal of immunopharmacology最新文献

A variety of cellular immune responses involve complement factors which bind to specific receptors, and modulate or effect a specific reaction. Monoclonal antibodies (MAb) have been generated against complement receptors (CR) 1 and 3, which were utilized to investigate human allogeneic and Epstein-Barr virus specific cytotoxic cells in vitro. MAb OKM1, which binds to the C3bi CR (CR3), and MAb M710, which binds to the C3b/4b CR (CR1), inhibited the generation of both allogeneic and virus specific cytotoxic responses in vitro in a dose-dependent way; doses of 1 microgram/ml (or greater) completely abrogated the cytotoxic responses. Inhibition of these responses was observed when the MAb was added to the cultures at any time point except the last two days. In addition, treatment of the responder (but not the stimulator cells) with either MAb resulted in complete inhibition of cytotoxic responses. These experiment indicate that complement receptors participate in the generation of human cytotoxic responses in vitro.

Previous studies have provided pharmacologic evidence that T lymphocyte function may be regulated in part by the intracellular production of various arachidonic acid (AA) metabolites in response to cellular stimulation. However, the specific AA metabolic capabilities of homogeneous T cell populations have not been clearly defined. In the present studies, we have employed an accessory cell-free T cell line, HT-2, as a model system for the examination of stimulus-induced eicosanoid biosynthesis in T lymphocytes. HT-2 cells were biosynthetically labeled with [3H]-AA and challenged briefly with various agents that stimulate the hydrolytic release of AA from cellular phospholipids. The bee venom peptide melittin stimulated a profound AA release response in the cells and the concomitant synthesis of both cyclooxygenase (PGF2 alpha, PGE2 and PGD2) and lipoxygenase (5-,12-,15-HETE and possibly 5-,12-diHETE) metabolites of AA. The formation of PGs was blocked by 5 microM indomethacin, demonstrating that this cell line contains cyclooxygenase activity functionally similar to that described in macrophages and other cell types. The high activity of melittin in this system was shown to result largely from a synergy between the peptide itself and a persistent bee venom phospholipase A2 contaminant. However, experiments with melittin freed of detectable phospholipase A2 activity by heating, and with synthetic homopolymers of (L)-lysine and (L)-arginine demonstrated that HT-2 cells contain sufficient endogenous, stimulus-responsive phospholipase A2 to provide both the cyclooxygenase and lipoxygenase pathways of AA metabolism ith substrate. In contrast, Ca++ ionophores, which are known to stimulate AA release and metabolism in certain cell types, stimulated only AA release but no detectable eicosanoid biosynthesis in HT-2 cells. Experiments with exogenous bacterial phospholipase C suggested that this cell line can also generate free AA for eicosanoid biosynthesis from membrane-derived 1,2-diacylglycerol. These results indicate that multiple intracellular pathways of AA metabolism are present HT-2 cells, and that the stimulus-induced release of AA and the production of eicosanoid second messengers may result from activation of either phospholipase A2 or phospholipase C.

A number of representative flavonoids reversibly inhibit human lymphocyte proliferative responses in a concentration-dependent manner. The flavonoids quercetin and tangeretin are most effective when added during the early phase of exposure of lymphocytes to the mitogenic stimuli but become progressively less effective when added after increasing lengths of time following stimulation, suggesting an early flavonoid-sensitive step(s) in cell activation. In the proliferative response to phytomitogens, they do not act by inhibiting the early increase in calcium influx. They do not augment cellular cyclic-AMP concentration in basal or phytomitogen-stimulated lymphocytes nor reduce its increment in the presence of inhibitors of phosphodiesterase. At concentrations inhibitory to the proliferative response, quercetin (but not tangeretin) inhibits the calcium-activated, phospholipid-dependent protein kinase (C kinase). Certain flavonoids powerfully inhibit the uptake of thymidine into phytomitogen-stimulated lymphocytes but do not directly affect incorporation of already transported thymidine into newly synthesized DNA.

Cyclosporine A (CsA), one compound in the family of cyclosporines, has effectively modulated the course of S-antigen induced experimental autoimmune uveitis (EAU). Cyclosporines G (CsG) and D (CsD), related to CsA in structure, were evaluated in their ability to prevent or modulate EAU in Lewis rats. 10 mg/kg/day IM of CsA effectively prevented the expression of EAU when therapy began on the day of immunization, while the same dosage of CsG prevented EAU in 81% of animals, and CsD only in 33%. Higher concentrations of CsG (40 mg/kg/day) did effectively block manifestations of the disease. Topical administration of CsG did not prevent the expression of disease but local protection was seen when the 500 micrograms CsG was placed intracamerally into only one eye. The in vitro comparison of these cyclosporines' capacity to alter proliferation and IL-2 release of a rat T-cell line capable of inducing EAU showed marked differences. CsA appeared to be most effective at abrogating these cellular functions at all concentrations tested, while CsD was least effective. CsG, however, approached the effectiveness of CsA. CsG is felt to be markedly less nephrotoxic than CsA, the secondary effect that is most commonly encountered, and could potentially be useful in the treatment of human intra-ocular inflammatory disease.

A lyophilized extract from E. coli (OM-89) was studied for its immunomodulating properties and tolerance in humans. Its oral administration to healthy volunteers produced a selective increase in the active T-cell population without changes in other lymphocyte populations. A significant increase in the proliferative response to concanavalin A and phytohemagglutin was recorded, but not to pokeweed mitogen. No significant changes were observed in the serum levels of IgG, IgA and IgM. The clinical and biological tolerance of OM-89 was excellent, without any adverse side-effects or production of circulating immune complexes or of autoantibodies, while the in vitro investigation showed that it is not a mitogen. Thus in healthy subjects OM-89 seems to act mainly on the cell-mediated immune responses.

The effect of multiple sublethal doses of busulfan on the haemopoietic system of the Balb/c mouse was examined. FBC's bone marrow histology and bone marrow progenitor cell assays (CFU-E, BFU-E, CFU-GM and CFU-GEM) were performed. No effect was seen on FBC's or on marrow histology. However there was a significant depletion noted in the number of haemopoietic progenitor cells as measured by in vitro culture.

Stable activated macrophage hybridomas were generated by somatic cell fusion between Propionibacterium acnes-induced peritoneal exudate cells and NS-1 myeloma cells. Five cell lines were obtained and each was cloned by limiting dilution; 59 clones were obtained. The cells of 2 clones (MP4-4 and MP4-8) which adhered to the culture dishes were selected for further analysis. These hybridomas exhibited non-specific esterase and beta-galactosidase intracellularly, and asialo GM1, Mac-1, Ia antigens and Fc-receptors on their cell surface. They did not, however, show phagocytic activity or secrete lysozyme. These hybridomas (MP4-4 and MP4-8) secreted the cytotoxic factor without any stimulation. Furthermore strong cytotoxic activity was found in ascites and sera from nude mice inoculated with these hybridomas. These activated macrophage hybridomas should be very useful in studies on cancer immunology and the physiology of macrophages.

The low molecular weight fraction (mol wt less than 1,000) of Ehrlich cancer ascitic fluid has been known to enhance Listeria infection in mice. Chemical characterization of the entities in this fraction revealed four purine and pyrimidine analogues, i.e. uric acid, uracil, pseudouridine and 1-methyladenosine (m1Ado). When the effect of each of these components was studied on Listeria infection in mice, only m1Ado markedly enhanced the infection and killed the mice within a short period. The optimal enhancement was obtained when m1Ado was given intravenously to mice 3-6 days before the infection at a concentration of between 1 and 100 micrograms/mouse. On the other hand, uric acid, uracil and pseudouridine failed to show such an enhancing effect. m1Ado inhibited macrophage accumulation in the peritoneal cavity of mice after an intraperitoneal injection of phytohemagglutinin. Although m1Ado did not show any inhibitory effect on the phagocytic and bactericidal activities of macrophages in vitro, peritoneal macrophages obtained from mice which received m1Ado 3 days ahead revealed impaired bactericidal activity, suggesting the migration of different cell populations from the bone marrow of m1Ado-receiving mice. The results may suggest that m1Ado is a major factor in tumor ascites causing, in small doses, an impairment of macrophage functioning as can be detected in tumor-bearing hosts.

This phase I study demonstrates the immunostimulating properties of SLO4 administered by the oral route in the healthy volunteer. Responses to the test of DTH (delayed type hypersensitivity) were enhanced by SLO4 and the production of MIF (migration inhibiting factor) involved in this response was stimulated. These properties could be correlated with the previously demonstrated induction of interferon by SLO4.