Non-specific immune suppression by CD8+ T cells in Brugia pahangi-infected rats

Non-specific suppression of the immune response was investigated in Brugia pahangi-infected Lewis rats. The proliferative response of peripheral blood lymphocytes or splenic non-adherent cells to mitogens was significantly reduced by B. pahangi infection. The degree of hyporesponsiveness of splenic non-adherent cells to mitogens was comparable between microfilaremic and non-microfilaremic animals. The suppressed proliferative response of splenic non-adherent cells was restored by blocking with anti-CD8 monoclonal antibody. After separation of T cells into CD4+ and CD8+ subpopulations, only CD8+ T cells from B. pahangi-infected rats suppressed the proliferative response of normal spleen cells to concanavalin A. CD8+ T cells from normal rats had no suppressive effect. On the other hand, the proliferative response of CD4+ T cells to concanavalin A was comparable between normal and infected rats. These results suggest that CD8+ T cells participate in the non-specific suppression of immune response in experimental filariasis.