Transforming growth factor beta and immunosuppression in experimental visceral leishmaniasis.
Hamsters infected with Leishmania donovani develop a disease similar to human kala-azar. They present hypergammaglobulinemia, and their T cells do not respond to parasite antigens. This unresponsiveness has been primarily ascribed to defects in antigen-presenting cells (APCs), because these cells are unable to stimulate proliferation of parasite-specific T cells from immunized animals. In this study, we show that APCs (adherent spleen cells) from L. donovani-infected hamsters produce high levels of the inhibitory cytokine transforming growth factor beta (TGF-beta). Immunohistochemical studies with an anti-TGF-beta monoclonal antibody (MAb) showed that this cytokine is abundantly produced in vivo by the spleen cells of infected animals. In addition, high levels of TGF-beta are produced in vitro by infected hamster cells, either spontaneously or after stimulation with parasite antigen or lipopolysaccharide. Furthermore, in vivo-infected adherent cells obtained from spleens of L. donovani-infected hamsters caused profound inhibition of the in vitro antigen-induced proliferative response of lymph node cells from hamsters immunized with leishmanial antigens. Moreover, this inhibition was totally abrogated by the anti-TGF-beta MAb. These results suggest that the immunosuppression observed in visceral leishmaniasis is, at least in part, due to the abundant production of TGF-beta during the course of the infection.
Rodrigues
V
V
Immunology Laboratory, Medical School of Triângulo Mineiro, Uberaba, MG, Brazil. vrodrigues@mednet.com.br
Santana da Silva
J
J
Campos-Neto
A
A
D000818:Animals; D006224:Cricetinae; D007108:Immune Tolerance; D007898:Leishmaniasis, Visceral / Q000276:immunology*; D051379:Mice; D016212:Transforming Growth Factor beta / Q000096:biosynthesis*
D016212:Transforming Growth Factor beta