M.G.B. Nieuwland

PHAGOCYTIC ACTIVITY OF TWO LINES OF CHICKENS DIVERGENTLY SELECTED FOR ANTIBODY PRODUCTION

Differences in phagocytic capacity of two chicken lines selected for high (H) or low (L) antibody response against sheep red blood cells (SRBC) were studied in 8 month old cocks of the seventh selection generation. The H line cocks had significantly higher agglutinin titers after immunization with SRBC than the L line. The total clearance capacity of the phagocytes, measured by the clearance of carbon particles from the blood, did not differ between the lines. The L line cocks had more circulating granulocytes. However, the granulocytes of the H line phagocytized more yeast cells than those of the L line. Neither in immunized nor in non-immunized cocks, were line differences found in the intracellular destruction of antigen by phagocytes, estimated as the superoxide production during phagocytosis and the plasma levels of lysozyme activity and acid phosphatase, before and after immunization. It was concluded that the line difference in antibody response was not due to measurable differences in phagocytic activity.

Effects of route of immunization, adjuvant and unrelated antigens on the humoral immune response in lines of chickens selected for antibody production against sheep erythrocytes

Effects of intramuscular (i.m.), intravenous (i.v.) and intraperitoneal (i.p.) primary immunization with the T-dependent antigen, sheep red blood cells (SRBC), was studied in two chicken lines selected for either high (H) or low (L) antibody response after i.m. immunization with SRBC. The primary route of immunization affected the line differences in the primary response and in the secondary response after i.m. reimmunization. Intravenous immunization with the T-dependent antigen bovine serum albumin (BSA) showed line differences similar to those found after i.m. or i.v. immunization with SRBC. Immunization with both the partially T-independent antigens Brucella abortus (BA) or Salmonella H-antigen (SHA) revealed no line effect. Immunization with SRBC in incomplete Freunds adjuvant (IFA) did not change the difference between lines, whereas immunization with complete Freunds adjuvant (CFA) diminished the difference between lines. It is postulated that differences in antibody production between the selected lines might be attributed to differences in T-cell activity.

The Biozzi model applied to the chicken.

Resistance to infectious diseases is influenced by environmental factors as well as genetic constitution. Qualitative and quantitative inheritance of resistance is known for a variety of poultry diseases. However, genes directly responsible for resistance or susceptibility have not yet been identified. In this paper the direct and correlated responses to selection for antibody production to sheep red blood cells (SRBC) are presented and the strategy to identify the genes responsible for antibody production to SRBCs will be discussed. After seven generations of selection for antibody production to SRBCs we have obtained high (H) and low (L) antibody titer producing lines of ISA Warren origin. Differences in antibody production (titer 7.1 versus 2.1 for H and L lines in the seventh generation) became significant (P<0.5) from the first selection onwards. Upon contact exposure to Marek’s disease virus the H line showed 20–30% less mortality than the L line (P<0.001). The divergence in H and L lines demonstrates that genetic variation in immune responsiveness and disease resistance exists and exemplifies genetic differences between breeds and crosses in poultry production. As has previously been demonstrated in the mouse, genes contributing to these immunological and pathological differences between H and L lines may belong to polymorphic immunoglobulin (Ig) loci and/or loci of the major histocompatibility complex (MHC). To establish the role of these loci in the chicken, F1 and F2 generations will be obtained by crossing the H and L lines. In the F1 and F2 hybrids background genes of H and L lines will be randomly distributed, with the application of serological techniques for identifying Ig-allotypes and MHC-alleles it will then become possible to determine the effects of the individual alleles on SRBC antibody production and resistance to Marek’s disease.