RESUMO
The role that T and B lymphocytes play in the clearance of Giardia muris in the mouse model is well known, but the cytokines produced by CD4+ T cells in response to Giardia antigenic stimulation are unknown. In this study, we have determined how Giardia trophozoite antigenic crude extract and T cell mitogens can trigger the production of cytokines by Peyer's patch and spleen cells removed from infected animals. When Giardia trophozoite proteins were used to challenge the cells in vitro, IL-4, IL-5 and IFN-gamma were not detected in the culture supernatant. When the cells were challenged with Con-A, all three cytokines were released in vitro. However, the level of each cytokine released by the spleen or Peyer's patch cells varied with the latent, acute and elimination phases of the infection. The high levels of IL-4 and IL-5 released by Peyer's patch cells confirm the importance of IgA in the control of the infection. However, we propose that the relative success of G. muris in completing its life cycle in a primary infection might be due, in part, to the stimulation of a Th2-type response (IL-4, IL-5). A stronger Th1 response (IFN-gamma) may lead to a better control of the primary infection.