Abstract
One of the most characteristic clinical features in cutaneous leishmaniasis is the development of nodules followed by ulcerations at the site of infection. 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, the roles of T cells in ulceration were examined using SCID mice in cell reconstitution experiments. After development of nonulcerative nodules, SCID mice were inoculated with splenocytes from either Leishmania-infected or naive immunocompetent mice, resulting in ulceration in all mice. When naive splenocytes were depleted of CD4(+), CD8(+), or B220(+) cell populations and the remaining cells were injected into Leishmania-infected SCID mice after the development of nodules, only SCID mice inoculated with splenocytes depleted of CD4(+) cells did not show ulceration. The evidence obtained in this study clearly shows that the CD4(+) cell population is indispensable for ulceration in leishmaniasis lesions of SCID mice.