Submitted to: NE-60 Regional Meeting
Publication Type: Experiment Station
Publication Acceptance Date: December 6, 1999
Publication Date: N/A
Interpretive Summary: Coccidiosis in chickens is caused by several different species of Eimeria parasites, which damage the intestinal tissues of infected chickens. Currently, coccidiosis is managed by prophylactic medication and live parasite vaccination. ARS scientists are developing new control strategies to reduce economic losses due to coccidiosis. This report describes new research findings, which indicate that natural factors, which are secreted by chicken macrophages and lymphocytes, can mediate protective immune response against Eimeria parasites. This basic knowledge will lay ground work for future development of immunological control strategy against coccidiosis.
Macrophages, activated during the inflammatory phase of a host's immune response, play a major role in defense against infections through their high output, sustained production of NO, catalyzed by iNOS. The results of our studies on NO production in two inbred chicken lines are consistent with the idea that the genetics of resistance of chickens to E. tenella infections is complex. The SC strain, which is considered resistant, appears to express a heightened iNOS response to infection compared to the TK strain. This report also showed that recombinant chicken IFN-gamma demonstrates anti-viral activity and activates macrophages. We also showed that chicken IFN-gamma not only increases the percentage of class I and class II MHC antigen positive cells, but also enhances other antigen expression on macrophages. These results indicate that one of the ways in which IFN-gamma immunoregulates macrophage activity is by upregulating cell surface antigens involved in host immune responses. The availability of chicken rIFN-gamma will now enable further characterization of the role of this cytokine in host immune responses in normal and diseased chickens. Lastly, three crucial evidence indicates that the gene encoding gamma/delta T cell growth factor in the chicken IL-15; 1) The wide tissue distribution; 2) the presence of conserved cysteine residues as in the mammalian IL-15s, and ;3) the ability of recombinant IL-15 to support the growth of gamma/delta T cells.