Patients with acute kala azar are generally nonreactive in a number of immunologic assays, including T cell proliferation and generation of macrophage-activating cytokines, principally IFN-'y, in response to leishmania antigens in vitro. To test for potential immunosuppressive factors, a series of T cell lines and clones were established from patients with acute kala azar, from patients after chemotherapy for kala azar, and from skin test-positive adults from the same endemic region. Although CD4+ T cell lines and clones could be readily established from the skin test-positive adults, lines and clones from acute or treated patients were heavily biased in expression of CD8+. The CD8 + cells from acute patients did not themselves release cytokines in response to leishmania antigens in vitro, but markedly affected the cytokine profile of peripheral blood mononuclear cells isolated 1 yr later after recovery. Addition of the CD8 + cells caused inhibition of lymphoproliferation and IFN-y release, with augmentation of IL-6 and IL-10 release. The inhibitory effects of the CD8+ cells could be partially abrogated by antibodies to IL-10 but not by antibodies to IL4. Analysis of four patients with acute kala azar demonstrated release of IL-10 that could not be demonstrated in supernatants from asymptomatic skin test-positive individuals. Generation of IL-10 may contribute to the profound suppression of IFN--y release that occurs during kala azar due to Leishmania chagasi. (J. Clin. Invest. 1993. 92:2626-2632.) Key words: leishmania -interleukin-10 * kala azar * interferon-'y -immunosuppression

Patients from across the spectrum of clinical manifestations of Leishmania chagasi infection were evaluated for in vitro correlates of immunity. Peripheral blood mononuclear cells were assayed for parasite-specific lymphoproliferation, cytokine generation, and the capacity to activate autologous macrophages to kill intracellular amastigotes. Patients with acute kala-azar were generally unreactive in each of these assays. Children with subclinical infection demonstrated relatively low levels of proliferation and interferon-gamma production, but none went on to develop overt kala-azar during the study. Patients evaluated after therapy for kala-azar demonstrated yet higher levels of lymphoproliferation and cytokine generation and produced low but significant levels of cytokines in vitro in response to parasite antigens, but not during the activation of infected macrophages. Finally, peripheral blood mononuclear cells from adults with positive delayed-type hypersensitivity responses and no history of kala-azar showed the broadest reactivity in vitro. These patients' cells generated the largest amounts of activating cytokines in vitro during the activation of autologous macrophages to a leishmanicidal state.

In order to evaluate the aplicability of the Direct Agglutination Test (DAT) as a method of detection of the natural canine infection for Leishmania (Viannia) braziliensis, it was realized a study involving the serum of naive dogs from Serra de Baturite, Ceara State, an endemic area of cutaneous leishmaniasis, and others from Curitiba, Parana State, a non endemic area. The results indicate the possibility of using this sorologic test to the epidemiologic research of the infection in the reservoir host; in this case, the dog.