Influence of antigens and adjuvants on the production of gamma-interferon and antibody by ovine lymphocytes.

The production of gamma-interferon (gamma-IFN) and antigen-specific immunoglobulin isotypes was monitored in sheep given primary and secondary inocula of protein and polysaccharide antigens with or without adjuvants. In efferent lymph from prefemoral nodes draining the site of inoculation, gamma-IFN levels increased within 24 h after injection of adjuvants Quill A, dextran sulfate (DXS) and 6 days after oil adjuvants in saline. The increased synthesis of gamma-IFN was prolonged by 1-2 days by the presence of adjuvanted antigen, but the major stimulus to gamma-IFN production was provided by the adjuvant. Alhydrogel (AH) did not initiate gamma-IFN synthesis. Following a second inocula of antigen in saline, increased levels of gamma-IFN were detected in efferent lymph after 3-4 h, and persisted for at least 2 days. Following cultivation of leucocytes from immunized sheep with specific antigen in vitro, strong positive correlations between levels of interleukin (IL) IL-2, gamma-IFN, proliferative responses and antibody titres were observed. However, after analysis of the antigen-specific isotypes of immunoglobulin (Ig) there was no correlation between the production of gamma-IFN and particular Ig isotypes. Together with findings that AH did not preferentially induce IgG1 or IgG2, these results suggest that the specific subpopulations of helper T lymphocytes which regulate the production of antibody isotypes by differential secretion of gamma-IFN or IL-4, are not as clearly defined in sheep as in mice.