Chicken Mhc alloantiserum cross-reactivity analysis by hemagglutination and flow cytometry.

The major histocompatibility complex (Mhc) haplotype in the chicken is generally determined by the use of alloantisera in a hemagglutination assay. This method restricts haplotype determination to antigens expressed on the surface of erythrocytes which includes class I (B - F) and class IV (B - G) antigens as well as any other polymorphic molecules on these cells. Alloantisera can result in complex cross-reactivity patterns. We describe here the analysis of 53 alloantisera made within Mhc-congenic lines. Each antiserum was tested by hemagglutination with erythrocytes and by flow cytometry with erythrocytes and peripheral white blood cells of seven Mhc haplotypes; B2, B5, B12, B13, B15, B19 , and B21 . Five types of antiserum were identified based on their reactivity to different cell subpopulations of the peripheral blood of the donor haplotype as well as in cross-reactivity for different haplotypes. RBC specific cross-reactive antigens attributed to B - G molecules were demonstrated for the B5 : B19, B12 : B19, and B19 : B21 cross-reactions. Cross-reactive antigens detected on RBC and thrombocytes attributable to B - G molecules on both types of cells were demonstrated for the B2 : B12, B2 : B15, B2 : B19, and B2 : B21 cross-reactions. In addition, cross-reactive antigens occurring on RBC and WBC were attributed to B - F (or RBC and lymphocyte-expressed B - G loci) and included the B12 : B13, B13 : B19, and B15 : B19 cross-reactions. Several antisera with specificity for B cells purportedly identifying B - L epitopes were found but their numbers were limited and cross-reactivities were not defined. The identities described here may be useful in understanding B haplotype similarities and differences in disease resistance and immune response.