DEPLETION OF CD8-CELLS FOLLOWING PRIMARY IMMUNIZATION WITH OVALBUMIN RESULTS IN A HIGH AND PERSISTENT IGE RESPONSE( T)

The role of CD8+ T cells in the regulation of IgE was investigated by in vivo CD8+ T-cell depletion. Following intraperitoneal immunization with ovalbumin (OVA), OVA-specific T cell responses were first detecte d in the draining lymph nodes (LN) and subsequently in the spleen. In vitro depletion of LN CD8+ cells reduced the OVA-specific LN CD4+ T ce ll response; while depletion of splenic CD8+ cells enhanced the OVA-sp ecific splenic CD4+ T cell response, suggesting an early helper and la ter suppressor function. CD8+ cell depletion in vivo up to 7 days afte r immunization failed to enhance IgE production, but depletion of CD8 T cells between day 12 and day 18 increased IgE levels to over 10 mu g/ml. Adoptive transfer of 1x10(7) purified CD8+ T cells (>95% CD8+ >9 8% CD3+ <1% NK, <1% CD4+ from parallel immunized rats or of 1x106 cell s of an OVA-specific, MHC class I restricted CD8+ T cell line suppress ed the IgE, but not Igc, response by >95%. These results provide furth er evidence that CD8+ T cells inhibit IEE production, possibly by prev enting the generation of adequate amounts of appropriate CD3+ T cell h elp.