RESPONSE TO SALMONELLA-ENTERITIDIS INFECTION BY THE IMMUNOCOMPROMISEDAVIAN HOST

To develop knowledge of the avian immune response and improve the abil ity of chickens to resist infection by Salmonella enteritidis (SE), th e role of the different components of the immune response against SE i nfection was examined. Birds were given treatments with cyclophosphami de, cyclosporine A, or testosterone propionate to induce immunological deficiency, and experiments were performed to determine the effects o f each on the immune response. Each treatment reduced hatch rate, surv ival rate, and rate of weight gain. As measured by flow cytometry, tre atments with cyclophosphamide and testosterone propionate decreased th e percentages of B cells to background levels and increased the percen tages of CT8 cells significantly above controls. The intestinal shed r ate of SE increased after treatment with testosterone propionate and c yclophosphamide, but dissemination to the spleen of infected birds was not different from controls for any treatment. The SE infection was a lso immunosuppressive as measured by the proliferative response to mit ogenic stimulation. Maximum lymphocyte proliferation occurred 1 wk aft er infection in response to .5 mu g concanavalin A per 10(6) cells. By the 2nd wk, proliferation dropped 10-fold to almost no response. Resu lts showed that immunocompetence relied on interdependent functions of multiple components of the immune response, i.e., aspects of both hum oral and cell-mediated immunity.