The role of B7 molecules in the cell contact-mediated suppression of T cell mitogenesis by immunosuppressive macrophages induced with mycobacterial infection.
We found previously that immunosuppressive macrophages (Mphis) induced by Mycobacterium intracellulare infection (MI-Mphis) transmitted their suppressor signals to target T cells through cell contact with target T cells. In this study, we examined what kinds of Mphi surface molecules are required for such cell-to-cell interaction. First, it was found that a B7-1-like molecule (B7-1LM) recognizable with one of three test clones of anti-B7-1 monoclonal antibodies (mAbs) was required for expression of the Mphi suppressor activity. Neither anti-B7-2, anti-ICAM-1, nor anti-VCAM-1 mAb blocked the Mphi suppressor activity. Second, MI-Mphis increased the expression of B7-1LM in parallel with the acquisition of the suppressor activity. Moreover, MI-Mphis bound with target T cells in a B7-1LM-dependent fashion. Third, mAb blocking of CTLA-4 on target T cells did not reduce the suppressor activity of MI-Mphis, suggesting the role of a putative molecule on target T cells other than CTLA-4 as the receptor for B7-1LM of MI-Mphis. Fourth, concanavalin A (Con A) stimulation of MI-Mphis was needed for effective cell contact with target T cells and subsequent expression of the suppressor activity of MI-Mphis. Fifth, the Con A-induced increase in the suppressor activity of MI-Mphis was inhibited by KN-62 but not by herbimycin A, H-7, nor H-88, indicating that Con A-induced up-regulation of MI-Mphi function is mediated by calmodulin-dependent protein kinase II or ATP/P2Z receptors, but independent of protein tyrosine kinase, protein kinase C, and protein kinase A. These findings indicate that a B7/CTLA-4-independent mechanism is needed for the transmission of the suppressor signals from MI-Mphis to target T cells.
Department of Microbiology and Immunology, Shimane University School of Medicine, Izumo, Japan.
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Shimizu
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Sano
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Tomioka
D000818:Animals; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000378:metabolism; D018122:B7-1 Antigen / Q000276:immunology*; D015153:Blotting, Western; D060908:CTLA-4 Antigen; D002450:Cell Communication / Q000276:immunology; D002478:Cells, Cultured; D003208:Concanavalin A / Q000276:immunology; D007108:Immune Tolerance / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology; D008262:Macrophage Activation / Q000276:immunology; D008264:Macrophages / Q000276:immunology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D015270:Mycobacterium avium-intracellulare Infection / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
D015703:Antigens, CD; D000943:Antigens, Differentiation; D018122:B7-1 Antigen; D060908:CTLA-4 Antigen; C556707:Ctla4 protein, mouse; D003208:Concanavalin A