Control of Trypanosoma cruzi infection in mice deprived of T-cell help.
The role of CD4+ T lymphocytes in the resistance of BALB/c mice to Trypanosoma cruzi was examined by in vivo depletion using monoclonal anti-CD4 antibodies (MoAbs). When the administration of MoAbs was initiated 2 days before, or 5 to 12 days after the infection (dpi) with 50 bloodstream-form trypomastigotes of the Tulahuén strain, mice showed an enhanced susceptibility to the parasite. Specific IgG, but not IgM responses, were inhibited in anti-CD4-treated and infected mice. However, when anti-CD4 treatment of mice was delayed until the 8th week of infection, neither a reactivation of the infection as determined by mortality or parasitaemia, nor a modulation of the titre of anti-T. cruzi IgG antibodies was detected. Furthermore, mice chronically infected with T. cruzi and deprived of CD4+ T cells resisted the challenge with 50,000 trypomastigotes (approximately 1000 LD50). Secondary antibody responses against parasite antigens were inhibited after in vitro depletion of CD4+ cells in chronically infected mice before boosting with T. cruzi antigens. However, recipients of CD4 or T-cell-depleted spleen cells from mice chronically infected with T. cruzi were protected when challenged with the parasite. The possibility that the parasite control is maintained by long-lived B cells capable of rapid differentiation into IgG-secreting plasma cells in the absence of T helper cells is discussed considering the present data.
Department of Immunology, Karolinska Institute, Stockholm, Sweden.
M E
ME
Rottenberg
D A
DA
Rodriguez
A
A
Orn
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001402:B-Lymphocytes / Q000502:physiology; D015704:CD4 Antigens / Q000502:physiology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D014355:Chagas Disease / Q000276:immunology*; D016219:Immunotherapy, Adoptive; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C
D000911:Antibodies, Monoclonal; D015704:CD4 Antigens