In vivo adjuvant effect of interleukins 5 and 6 on rat tear IgA antibody responses.

Interleukins 5 and 6 have previously been shown to exhibit IgA-enhancing activity in vitro. This study investigated the effect of IL-5 and IL-6 on antigen-specific tear IgA antibody responses in vivo. Rats were given primary and secondary immunizations by the ocular-topical (OT) route with either antigen (DNP-Pn) alone or antigen plus IL-5 and IL-6 (IL-5/6). Antigen was administered for the first 3 days of each stimulation cycle and lymphokines (50 units of each lymphokine/eye/day) or control media for the first 7 days of the primary and secondary immunizations. Co-administration of antigen with IL-5/6 markedly enhanced (approximately three-fold) the secondary tear IgA anti-DNP antibody response in the lymphokine-treated group. Enhanced tear IgA antibody responses were maintained in the lymphokine-treated group following a tertiary immunization in the absence of IL-5/6. There was no apparent effect on the total tear IgA levels in either group of animals. Ocular topical immunization also elicited secondary and tertiary serum IgG antibody responses which were not affected by the administration of IL-5/6. Neither secondary nor tertiary serum IgM antibody responses were detected in either group of animals. These data indicate that IL-5 and IL-6 are able to augment tear IgA antibody responses in vivo. That the enhancement was maintained following a subsequent antigenic challenge in the absence of the lymphokines suggests a potential therapeutic application for lymphokines in augmenting IgA responses at mucosal surfaces.