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Background: Mast cells (MC) are key effector cells of allergic diseases and resistance to helminthic parasites and induce or amplify diverse innate and adaptive immune responses. The signals controlling MC mobilization during inflammation are not fully understood. Results: Since anaphylatoxins are attractive candidates as MC chemoattractants, we investigated expression and function of anaphylatoxin receptors in murine MC. Precursor cell-derived MC cultured with IL-3 in the presence or absence of SCF did not express significant amounts of surface C5a receptor (C5aR) or C3a receptor (C3aR). MC required approximately 4 h of stimulation with Ag (DNP-albumin, following preincubation with IgE anti-DNP), ionomycin, or PMA to enable a strong chemotactic response towards C5a, paralleled by a distinct C5aR upregulation. Likewise, C5a induced intracellular calcium fluxes solely in activated MC. In contrast, C3a proved to be a weak MC chemotaxin and unable to increase intracellular calcium. Primary peritoneal MC did not express detectable amounts of anaphylatoxin receptors, however, similar to precursor cell-derived MC, stimulation with Ag or ionomycin for 4 h induced a prominent surface expression of C5aR whereas C3aR remained undetectable. Conclusion: Collectively, our results suggest that Ag-dependent as well as -independent activation induces an inflammatory MC phenotype which is distinguished by neoexpression of a functional C5aR as a novel effector mechanism in MC-mediated pathogenesis. [ABSTRACT FROM AUTHOR]

Summary The morbidity and lethality of tuberculosis is partially the result of an ineffective delayed-type hypersensitivity reaction which causes caseating granulomas in the lung and other organs. Recently we showed that during caseation besides macrophages numerous Fas+ FasL+ lymphocytes undergo apoptosis and postulated that this phenomenon may be due to activation-induced cell death (AICD) as a consequence of T-lymphocyte reactivation via bacillary antigens. As purified protein derivative of Mycobacterium tuberculosis (Mtb-PPD) provokes caseation in tuberculosis patients, the question arose as to whether bacillary antigens are responsible for AICD within caseous areas. In the present study Mtb-PPD-specific T helper 1 (Th1)-differentiated T lymphocytes were generated in vitro. Reactivation of these cells with Mtb-PPD resulted in a concentration-dependent hyporesponsiveness, which was due to an increase in apoptosis of γδ+, αβ+ CD4+ as well as αβ+ CD8+ T lymphocytes as assessed by the demonstration of the apoptosis-associated mitochondrial membrane protein 7A6 and DNA fragmentation. Blocking experiments demonstrated that Mtb-PPD antigens exploited the Fas/FasL system to induce apoptosis in Mtb-PPD-specific T lymphocytes. These results may support the hypothesis that in tubercle granulomas with caseation T lymphocytes undergo AICD following reactivation by bacillary antigens, thus contributing to the persistence of tuberculosis. [ABSTRACT FROM AUTHOR]

Due to their central role in controlling immunity, dendritic cells are logical targets for priming naive cytotoxic T lymphocytes against tumour cells. In a strictly autologous system, we fused dendritic cells with melanoma cells, both of which were derived from patients with metastatic malignant melanoma. Hybridomas were positive for major histocompatibility complex (MHC) class II, CD40, CD54, CD83, CD86, and the pro-inflammatory cytokine interleukin-12. Autologous T lymphocytes were co-incubated with hybridomas. After 6 days, in-vitro-primed T lymphocytes revealed a strong proliferation activity and released Th-1-associated, but not Th-2-associated, cytokines. Furthermore they showed effective anti-melanoma activity, resulting in death of 70 ± 9% of autologous melanoma cells. After depletion of CD4+ cells from the mixed population of primed T lymphocytes, the remaining CD8+ cells were able to kill 63 ± 8% of autologous melanoma cells. Following depletion of CD8+ cells, however, the cytotoxic capacity of the remaining T lymphocytes caused death in only 32 ± 6% of autologous melanoma cells. Blocking of MHC class I, but not class II, molecules on hybridomas impaired T cell proliferation, secretion of Th-1-associated cytokines, as well as the cytotoxic activity of primed T cells. These findings strongly suggest that hybridomas deliver melanoma-associated antigens via MHC class I molecules to T lymphocytes, resulting in the generation of CD8+ cytotoxic T lymphocytes with effective anti-melanoma activity in vitro. The data may serve as a basis for the use of hybridomas in the immunotherapy of malignant melanoma in vivo. [ABSTRACT FROM AUTHOR]