concanavalin-a and Trypanosomiasis--Bovine

In this study the involvement of peripheral gamma delta T cells, prepared by flow cytometry, in the immune response of cattle to primary infection with Trypanosoma congolense was assessed. Negligible in vitro proliferative responses were observed in gamma delta T cells isolated from trypanosusceptible Boran (Bos indicus) cattle at all stages examined post-infection when stimulated in vitro with parasite antigens. In contrast, both CD8+ T cells and gamma delta T cells from trypanotolerant N'Dama (Bos taurus) cattle proliferated markedly when stimulated in vitro with a complex of invariant trypanosome antigens with MW between 100,000 and 140,000 (100,000 MW complex). Neither species of cattle exhibited significant T-cell recognition of trypanosome variable surface glycoprotein (VSG). To study further the functional and phenotypic characteristics of the gamma delta T-cell response, four T-cell lines were established from infected N'Dama cattle. These cell lines were comprised of up to 96% gamma delta (WC1+) T cells, the remainder being CD8+ T cells. Two of these gamma delta T-cell lines exhibited 100,000 MW complex antigen specificity which was not major histocompatibility complex (MHC) restricted in one line.

Topics: Animals; Antigens, Protozoan; Cattle; Cell Line; Cells, Cultured; Concanavalin A; Molecular Weight; Receptors, Antigen, T-Cell, gamma-delta; T-Lymphocyte Subsets; T-Lymphocytes; Trypanosoma congolense; Trypanosomiasis, African; Trypanosomiasis, Bovine; Variant Surface Glycoproteins, Trypanosoma; Viral Vaccines

Tsetse-transmitted Trypanosoma congolense infection causes an impairment of in vitro T cell proliferative responses in Boran (Bos indicus) cattle. To assess the importance of this phenomenon as it may relate to the ability of trypanotolerant cattle to control infection with trypanosomes, T cell proliferative responses to mitogenic stimulus with Concanavalin A were measured in N'Dama (Bos taurus) cattle throughout infection. The responses of peripheral blood mononuclear cells from Boran and N'Dama cattle were similar. Depressed proliferative responses were observed with cells of both breeds at 12 days post infection, after which the responses returned to levels similar to those recorded pre-infection. Immunosuppression was also studied in the lymph nodes of a major histocompatibility complex (MHC)-matched pair of N'Dama cattle. Lymph node cells from the infected animal failed to respond to mitogenic stimulus. Co-culture experiments in which the cells from this node were mixed with either lymph node cells or peripheral blood mononuclear cells from the non-infected MHC-compatible animal revealed the presence of suppressor cells, acting in a prostaglandin-independent manner, capable of arresting mitogen-induced T cell proliferation.

Topics: Animals; Cattle; Cells, Cultured; Concanavalin A; Immune Tolerance; Immunosuppression Therapy; Lymph Nodes; Lymphocyte Activation; Major Histocompatibility Complex; T-Lymphocytes; T-Lymphocytes, Regulatory; Trypanosoma congolense; Trypanosomiasis, African; Trypanosomiasis, Bovine

Impairment of T-cell function in Boran (Bos indicus) cattle during primary infection with Trypanosoma congolense ILNat 3.1 was found to occur in peripheral blood, spleen and, in particular, the lymph nodes. Lymph node cells from infected cattle failed to proliferate in response to mitogenic stimulus and suppressed proliferation of both normal peripheral blood mononuclear cells and lymph node cells in co-culture assays. The addition of indomethacin, to inhibit prostaglandin synthesis, had no effect on the ability of lymph node cells from infected cattle to suppress the proliferative response of responder cells from uninfected cattle. The supplementation of the culture media with catalase, which degrades hydrogen peroxide, either alone or in combination with indomethacin, also did not result in restoration of proliferation. This suggested the presence of suppressor cells in lymph nodes of infected cattle which exert their effects via a prostaglandin-independent mechanism. By depleting lymph node cells from infected cattle of the monocyte-macrophage population using a cell sorter it was possible to abrogate the previously observed immunosuppression, thus indicating a key role for these macrophages in the induction of trypanosome-associated immunosuppression.

Topics: Animals; Cattle; Cell Division; Cells, Cultured; Concanavalin A; Immune Tolerance; Lymph Nodes; Macrophages; Prostaglandins; T-Lymphocytes; Trypanosoma congolense; Trypanosomiasis, Bovine