Escherichia coli challenge in chickens selected for high or low antibody response and differing in haplotypes at the major histocompatibility complex.

Relative sensitivity to Escherichia coli challenge was evaluated in white leg-horn chickens that had been selected for high antibody (HA) or low antibody (LA) response and that differed in haplotypes at the major histocompatibility complex (MHC). Assessments were made of relative body-weight change and of heart and air-sac lesions after inoculation of 10(6), 10(5), or 10(4) E. coli via the posterior thoracic air sac. As has previously been reported, chicks from line HA were more sensitive to E. coli than those from line LA. Lesion scores were 1.58 +/- 0.12 in line HA and 1.02 +/- 0.12 in line LA (mean +/- S.E.), and ranged from 0.99 +/- 0.14 with the lowest dose of E. coli to 1.79 +/- 0.15 for the highest dose. Relative body-weight change to 72 hours after inoculation was greater in line LA (7.5 +/- 0.5) than in line HA (4.4 +/- 0.8). There was no apparent resistance or susceptibility conferred to chickens in either the HA or LA genetic background as a result of haplotypes present at the MHC.