EFFECTS OF DEPLETION OF T-CELL SUBPOPULATIONS ON THE COURSE OF INFECTION AND ANTIPARASITE DELAYED-TYPE HYPERSENSITIVITY RESPONSE IN MICE INFECTED WITH BABESIA-MICROTI AND BABESIA-RODHAINI

To elucidate the role of T cell subpopulations in the protective cell- mediated immune response at the initial phase of infection with Babesi a microti (BM) and B. rodhaini (BR), the changes in the course of infe ction and anti-parasite delayed type hypersensitivity (DTH) response a fter BM or BR inoculation were investigated in Lyt-2(+) T cell- or L3T 4(+) T cell-depleted mice. Depletion of Lyt-2(+) T cells strongly enha nced the resistance to BM infection, whereas it increased the suscepti bility to BR infection. In contrast, depletion of L3T4(+) T cells incr eased susceptibility to BM infection, while it enhanced resistance to BR infection. The anti-parasite DTH response in BM-infected mice was s ignificantly enhanced by depletion of Lyt-2(+) T cells, while signific antly reduced by depletion of L3T4(+) T cells. No effects of depletion of either Lyt-2(+) or L3T4(+) T cells on DTH response was observed in BR-infected mice. From these results, it was suggested that the roles of Lyt-2(+) and L3T4(+) T cells in the protective cell-mediated immun e response at the initial phase of infection were different between BM - and BR-infected mice, resulting in the difference in their course of infection.