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 allele s were simultaneously segregating for nine alloantigen systems, including t he MHC (B). Chicks from Ancona-derived (BB19)-B-19 females crossed with Whi te leghorn (BB21)-B-19 males were blood typed, resulting in genotypic categ ories for the A-E, C, D, H, I, L, and P loci with the objective of determin ing which, if any, of the eight non-MHC alloantigen systems influence or in teract 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,(TM) density gradient and were allowed to adhere to glass cov erslips. The resulting adherent monocyte monolayers were incubated with via ble Escherichia coil for 1 h and stained with Leukostat,(TM) and the phagoc ytic 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 sig nificant differences were noted relative to the B system genotype at 2 wk o f age ((BB21)-B-19 > (BB19)-B-19: P = 0.049), L at 4 wk ((LL1)-L-1 > (LL2)- L-1; P = 0.009), and P at 4 wk ((PP4)-P-4 > (PP1)-P-1; 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. T hese studies suggest that the L and P non-MHC alloantigen systems have the potential to influence immune responses by modulating phagocytic function i n chickens. Furthermore, this modulation seems to be independent of the B ( MHC) system.