CD4(+) cells are indispensable for ulcer development in murine cutaneous leishmaniasis

One of the most characteristic clinical features in cutaneous leishmaniasis is the development of nodules followed by ulcerations at the site of infec tion. Leishmania amazonensis-infected mice show similar ulcerative lesions. Leishmania-infected severe combined immunodeficiency (SCID) mice, however, have been shown to develop nonulcerative nodules. In the present study, th e roles of T cells in ulceration were examined using SCID mice in cell reco nstitution experiments. After development of nonulcerative nodules, SCID mi ce were inoculated with splenocytes from either Leishmania-infected or naiv e immunocompetent mice, resulting in ulceration in all mice. When naive spl enocytes were depleted of CD4(+), CD8(+), or B220(+) cell populations and t he remaining cells were injected into Leishmania-infected SCID mice after t he development of nodules, only SCID mice inoculated with splenocytes deple ted of CD4(+) cells did not show ulceration. The evidence obtained in this study clearly shows that the CD4(+) cell population is indispensable for ul ceration in leishmaniasis lesions of SCID mice.