Augmentation of Suppressed Antibody Responses in Mice During Experimental Chagas’Disease by T Helper Cells Activated in a Time‐Dependent Mode of Immunization

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Abstract
Mice infected with the protozoan parasite Trypanosoma cruzi, the causative agent of human Chagas’disease, develop immunosuppressed responses to heterologous antigens. Experiments were performed using infected mice in the acute stage of infection to assess immunoregulatory activities during induction of direct plaque‐forming cells (DPFC) to sheep erythrocytes (SRBC), hapten‐conjugated SRBC (TNP‐SRBC), and horse erythrocytes (TNP‐HRBC). Studies in vivo demonstrated that anti‐SRBC responses were best enhanced when T. cruz‐infected mice were injected with primed T cells derived from normal or infected mice immunized four days previously. The presence of enhancing capacities for DPFC responses by T cells from T. cruzi‐infected mice were also supported by experiments examining the hapten‐carrier effect. Preimmunization of infected mice with SRBC or HRBC four days before injection of hapten‐homologous (TNP‐SRBC or TNP‐HRBC) carrier resulted in markedly augmented anti‐hapten antibody responses. These results show that functional help provided by T cells activated during priming and exposed to a challenge dose of antigen (SRBC) in a time‐dependent mode can overcome the effect of immunosuppression in T. cruzi‐infected mice.