Mycobacterium bovis BCG-induced Th1 type CD4+ suppressor T cells act by suppressing IL-2 production and IL-2 receptor expression.
Induction of suppressor cells has been hypothesized to explain the variability in the efficacy of Mycobacterium bovis BCG vaccination against mycobacterial diseases. In this study, we induced suppressor T cells by in vitro stimulation of peripheral blood mononuclear cells obtained from BCG-vaccinated healthy subjects. These suppressor T cells were CD4+ and did not affect interleukin-1 production by adherent cells in response to BCG. However, they suppressed interleukin-2 (IL-2) production and IL-2 receptor expression by the responding cells. Exogenous addition of IL-2 could partially restore the responsiveness of the indicator cells. To further characterize the cells responsible for suppression, T cell clones were established by limiting dilution. All the established T cell clones expressed CD4 marker, proliferated in response to BCG, were cytotoxic for antigen-presenting cells, and suppressed the antigen-induced proliferation of the indicator cells. Both suppression and cytotoxicity were not mediated by soluble factors but required cell-to-cell contact and were HLA-class II restricted. These results suggest that preferential killing of antigen-presenting cells by CD4+ T cells may be responsible for in vitro observed suppression in our system.
Mustafa
A S
AS
Department of Microbiology, Faculty of Medicine, Kuwait University, Kuwait.
D001402:B-Lymphocytes; D001500:BCG Vaccine / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D004854:Herpesvirus 4, Human; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis*; D009163:Mycobacterium bovis / Q000276:immunology*; D015375:Receptors, Interleukin-2 / Q000378:metabolism*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
D001500:BCG Vaccine; D007376:Interleukin-2; D015375:Receptors, Interleukin-2