Alloantigen systems L and P influence phagocytic function independent of the major histocompatability complex (B) in chickens.

Synthetic parent stocks were designed to produce progeny among which alleles were simultaneously segregating for nine alloantigen systems, including the MHC (B). Chicks from Ancona-derived B19B19 females crossed with White leghorn B19B21 males were blood typed, resulting in genotypic categories for the A-E, C, D, H, I, L, and P loci with the objective of determining which, if any, of the eight non-MHC alloantigen systems influence or interact with the B system genotypes for blood monocyte phagocytic activity. Leukocytes obtained from whole blood at 2 and 4 wk were separated on a Fico/Lite LymphoH, density gradient and were allowed to adhere to glass coverslips. The resulting adherent monocyte monolayers were incubated with viable Escherichia coli for 1 h and stained with Leukostat, and the phagocytic monocytes and numbers of internalized bacteria per phagocytic monocyte were scored microscopically. The combined results from two separate trials demonstrated that the genotypes of the A-E, C, D, H, and I systems did not differ in the percentage of monocytes exhibiting phagocytosis, whereas significant differences were noted relative to the B system genotype at 2 wk of age (B19B21 > B19B19; P = 0.049), L at 4 wk (L1L1 > L1L2; P = 0.009), and P at 4 wk (P4P4 > P1P1; P = 0.047). The data were further analyzed to determine any interactions of P and L alloantigen genotypes with the B system genotypes; no such interaction was observed. These studies suggest that the L and P non-MHC alloantigen systems have the potential to influence immune responses by modulating phagocytic function in chickens. Furthermore, this modulation seems to be independent of the B (MHC) system.