Immunocompetences and Marek's disease resistance in three pairs of chicken lines selected for different immunological characters.

Three pairs of chicken lines selected for high (H) and low (L) graft vs. host reaction (GVHR) competences, serum immunoglobulin G (IgG) levels, and antibody responses to Leucocytozoon caulleryi were examined for their immunocompetences and Marek's disease (MD) resistance. The GVHR-H and GVHR-L lines were further divided into two sublines according to their major histocompatibility B genotype. Immune responses to sheep erythrocytes (SRBC), bovine serum albumin (BSA), and a lipopolysaccharide (LPS) were compared between the high and low lines of each pair of selected lines. Significant differences were found in responses to SRBC and LPS in IgG-selected lines and in response to BSA in Leucocytozoon-selected lines. In all three instances antibody titers of the H line were higher than those of the L line. The GVHR competence expressed by the splenomegaly index (SI) was also significantly different between the H and L lines of all three selected-line pairs. The SI values in the GVHR-selected and IgG-selected lines were higher in the H line than in the L line, whereas those in the Leucocytozoon-selected lines were lower in the H line. Differences in MD incidence and in MD mortality were found between the GVHR-selected B11B11 subline and the IgG-selected lines. In both instances the L line was more resistant to MD than the H line.