Development of resistance to Trypanosoma cruzi in mice depends on a viable population of L3T4+ (CD4+) T lymphocytes

Mice injected with monoclonal antibody to the L3T4+ (CD4+) cell membrane surface glycoprotein of T lymphocytes and immunized with antigens of Trypanosoma cruzi had reduced antibody and cell-mediated immune responses to the organism. Mortality in these mice was 100% following challenge with 1.5 x 10(5) trypanosomes, whereas controls had a 50% survival rate, indicating that T-cell activation and viable L3T4+ (CD4+) T lymphocytes are essential for the development of resistance.