ANALYSIS OF IMMUNIZATION ROUTE-RELATED VARIATION IN THE IMMUNE-RESPONSE TO HEAT-KILLED SALMONELLA-TYPHIMURIUM IN MICE

In examinations of the factors regulating the quality and quantity of the immune response to Salmonella typhimurium, we have shown previously that live and heat-killed preparations of S. typhimurium can induce gamma interferon-dominant and interleukin 4-dominant immune responses, respectively, upon intraperitoneal (i.p,) immunization of BALB/c mice, Using this system to investigate the role of the route of immunization in the immune response, we show in the present study that i.p. immunization with heat-killed S. typhimurium generates a quantitatively better immune response than does intradermal (i.d.) immunization, The quantitative differences observed between the i.p. and i.d. routes are apparent in the amount of S. typhimurium-specific antibodies produced, the extent of responses in T-cell proliferation assays, and the quantities of lymphokines generated, However, the ratios of immunoglobulin (Ig) isotypes [IgG1/IgG2a] are comparable and the relative dominance of interleukin-il over gamma interferon is seen in both i.p.- and i.d.-immunized mice, suggesting that the predominant T-cell effector pathways triggered are not qualitatively dependent on the route of immunization, An examination of the antigenic profile recognised by the B-cell and T cell responses in i.p.-versus i.d.-immunized mice shows that while the Western immunoblot patterns recognized by serum antibodies from the two groups of mice were not significantly different, T cells from i.p.-immunized mice recognized a broader spectrum of antigens in an immunoblot assay than did those from i.d.-immunized mice, These data suggest that there may be a significant difference in the antigen-processing ability of peritoneal and dermal antigen-presenting cells for complex antigenic formulations such as bacterial vaccines.