Effect of in vivo depletion of CD4+ T cells on experimental infection of susceptible BALB/c mice with Leishmania amazonensis.

The role played by CD4+ T lymphocytes in susceptible BALB/c mice infected with Leishmania amazonensis was investigated. Depletion of CD4+ T cells was achieved in experimentally infected mice by means of treatment with anti-CD4 monoclonal antibody (mAb), resulting in significant reductions in the size of lesions and in mortality when compared with control animals. Moreover, the parasite load in the depleted mice, as quantified by limiting dilution analysis, was about 10-times lower than in the control groups. In addition, the incidence of metastases in the depleted mice was significantly reduced, and their appearance delayed as compared to the control animals. These effects correlated with a selective depletion of CD4+ T cells in the spleens of the mAb-treated mice, suggesting a role for CD4+ T cells in the aggravation of L. amazonensis infection in BALB/c mice.