Cellular immunology
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Cellular immunology · Aug 2000
Mechanism of cytotoxicity induced by chimeric mouse human monoclonal antibody IDEC-C2B8 in CD20-expressing lymphoma cell lines.
With a new flow cytometric cytotoxicity assay, we examined the mechanism of action of chimeric mouse human anti-CD20 monoclonal antibody IDEC-C2B8. IDEC-C2B8 alone induced direct cytotoxicity in four of eight examined CD20-expressing lymphoma cell lines (RAJI, DAUDI, JOK-1, and WT100) at a concentration above 100 ng/ml. Moreover, after 4 h incubation in human serum, only a moderate complement-dependent cellular cytotoxicity (CDCC) was observed, whereas cytotoxicity increased markedly after 3 days of culture, indicating that combined direct cytotoxicity and CDCC were responsible. ⋯ ADCC was moderately enhanced by cytokine interleukin-2, whereas interleukin-12, interferon-alpha, and GM-CSF had no influence. Interestingly, we could demonstrate a correlation between CD32 expression on lymphoma cell lines and IDEC-C2B8-induced direct cytotoxicity, indicating that crosslinking of CD20 with CD32 may be involved in the mechanism of cytotoxicity. We propose that direct cytotoxicity, CDCC, and ADCC result in the marked elimination of CD20-expressing tumor cells observed after treatment with IDEC-C2B8.
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Cellular immunology · May 1999
Corynebacterium parvum- and Mycobacterium bovis Bacillus Calmette and Guerin-induced granuloma formation in mice lacking CD4 and CD8.
Granuloma formation is a T-cell-dependent inflammatory response that is important in the host defense against intracellular bacteria. The role of CD4 and CD8 molecules in the development of Corynebacterium parvum- and Mycobacterium bovis Bacillus Calmette and Guerin (BCG)-induced granulomas was examined in CD4/CD8 knockout (KO) mice. CD4/CD8 KO mice developed a greater granulomatous response to heat-killed C. parvum and heat-killed BCG than did control mice. ⋯ The absence of CD4 and CD8 therefore impaired the host defense against infection with BCG. alphabeta T-cells were present in the granulomas of both CD4/CD8 KO and control mice in similar numbers. Also the production of IFN-gamma mRNA was similar in the two groups. In conclusion, CD4 and CD8 are not essential to the granulomatous response against C. parvum and BCG, but contribute to the host defense against live BCG infection.
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Cellular immunology · Sep 1994
Oral tolerance to myelin basic protein induces regulatory TGF-beta-secreting T cells in Peyer's patches of SJL mice.
Oral administration of myelin basic protein (MBP) is an effective means of suppressing experimental autoimmune encephalomyelitis (EAE). In the Lewis rat model, we have previously shown that this effect is mediated by active suppression as T lymphocytes from animals orally tolerized to MBP suppress in vitro immune responses and in vivo adoptively transfer disease protection to naive recipients. This effect is mediated by the cytokine TGF-beta which is secreted by T cells from orally tolerized animals after being triggered by the oral tolerogen. ⋯ Furthermore, cells from Peyer's patches of animals fed MBP adoptively transferred protection to actively induced EAE. Thus, MBP-specific TGF-beta-secreting regulatory cells recovered from Peyer's patches after a single oral administration of MBP are not evident as measured by proliferation, but are capable of suppressing in vitro and in vivo cell-mediated immune responses. Peyer's patches appear to be an important site for the induction of cells which mediate the active suppression component of oral tolerance.
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The percentage of TNF alpha- and beta-positive cells was analyzed in hypertrophic scar (N = 13), normotrophic scar (N = 7), and normal skin (N = 6) biopsies using monoclonal antibodies and immunoperoxidase staining of cryostat tissue sections. Samples were first characterized for infiltrating cells. ⋯ In fact, in hypertrophic scar samples a positive staining with anti-TNF alpha mAb was restricted to 8% of tissue-infiltrating cells compared to 35.4% of the cells present in normotrophic scars; 12% of infiltrating cells were stained in normal skin sections. These results suggest that TNF alpha may be important for normal wound healing and that hypertrophic scarring might be partially a consequence of a low amount of TNF alpha.
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Cellular immunology · Jul 1990
TNF-alpha and IFN-gamma reverse IL-4 inhibition of lymphokine-activated killer cell function.
Recombinant IL-4 inhibits IL-2-induced lymphokine-activated killer (LAK) cell development of PBMC. We evaluated the effect of various cytokines in reversing IL-4-mediated LAK inhibition. PBMC were cultured in IL-2 (10-1000 u/ml) with or without IL-4 (2-100 u/ml) and tested for cytotoxicity against the NK-sensitive K562 cells and NK-resistant UCLA-SO-M14 cells. ⋯ Addition of other IL-2-induced cytokines such as GM-CSF (50 u/ml), M-CSF (250 u/ml), and IFN-alpha (10-10,000 u/ml) fails to reverse IL-4 inhibition. In addition to suppression of LAK induction, IL-4 also inhibits IL-2-induced IFN-gamma and TNF-alpha protein production in PBMC. The reversal of IL-4-mediated LAK inhibition by TNF-alpha and IFN-gamma may therefore be due to resupply of these endogenously suppressed cytokines.