IL-15-IGG2B FUSION PROTEIN ACCELERATES AND ENHANCES A TH2 BUT NOT A TH1 IMMUNE-RESPONSE IN-VIVO, WHILE IL-2-IGG2B FUSION PROTEIN INHIBITS BOTH

We have explored how IL-15 influences Th1 or Th2 type immune response in vivo. Intraperitoneal application of an IL-15-IgG2b fusion protein (FP) to mice did neither significantly affect the footpad swelling nor the production of hemagglutinizing antibodies in a delayed type hyper sensitivity reaction to sheep red blood cells. In contrast, in an esta blished murine Th2 model of sensitization to ovalbumin (OVA), IL-15-Ig G2b FP plus OVA sensitization resulted in massively accelerated and en hanced allergen-specific IgE and IgG1 antibody production. In vitro, s timulation of spleen cells from OVA-sensitized mice with OVA+IL-15 or OVA+IL-15-IgG2b resulted in a significantly enhanced IgE production. I L-4 secretion was significantly induced by IL-15 but not by IL-15-IgG2 b. An IL-2-IgG2b FP with the same Fc tail as the IL-15-IgG2b FP was us ed as control in both models. In striking contrast to the IL-15-IgG2b FP, IL-2-IgG2b significantly inhibited the Th2 type antibody productio n in vivo. The current study suggests that IL-15-IgG2b may be employed as a potent accelerator and enhancer of Th2 type immune responses in vivo, while IL-2-IgG2b can suppress the latter.