THE ROLE OF CD4 CELLS IN PROTECTIVE IMMUNITY TO BRUGIA-PAHANGI

The BALB/c mouse immunized sub-cutaneously (s.c.) with 45 kRad attenua ted third stage larvae (L(3)) of the lymphatic filarial nematode Brugi a pahangi is strongly immune to a challenge infection (75-100% reducti on in recovery at day six post challenge). Analysis of spleen cell sup ernatants from immunized mice re-stimulated in vitro, with parasite an tigen or the non specific T cell mitogen Con-A reveals a cytokine prof ile (IL-4, IL-5 and IL-9) which indicates that the Th2 subset of CD4 c ells has been expanded. In an attempt to formally prove a critical rol e for CD4 cells in immunity in this model system, immunized mice were given either anti-CD4 or anti-CD8 neutralizing antibodies. Administrat ion of anti-CD4 antibody had a significant and detrimental effect on t he immune response whereas anti-CD8 antibody had a negligible effect o n immunity. The efficacy, of antibody, in neutralizing their target ce lls was determined by fluorescence activated cell sorting analysis (FA CS). Spleen cells from anti-CD4 treated immunized mice, when re-stimul ated with parasite antigen had a significantly reduced potential to se crete IL-4, IL-5 and IL-9 in vitro and serum from these mice had reduc ed levels of parasite specific IgG and IgE. These results demonstrate a critical role for CD4 T cells in host protective immunity to B. paha ngi in vivo anti strongly suggest that some component of the Th2 respo nse plays an important role in the immune response elicited in this mo del system.