Date of Award

Winter 2006

Project Type

Thesis

Program or Major

Animal Sciences

Degree Name

Master of Science

First Advisor

Robert L Taylor

Abstract

Recombination between chicken major histocompatibility complex (MHC) class I B-F and class IV B-G genes has enabled more precise identification of genes controlling immune responses. Congenic lines, each containing a unique MHC recombinant, were developed with 99.9% genetic uniformity to inbred Line UCD 003 (B17B17). A new recombinant, R13 (BF17-BG23), originated in the tenth backcross generation for R1 (BF24-BG23). Two experiments tested the R13 immune response to bovine red blood .cells (BRBC) and Rous sarcoma virus (RSV).

A single R13B17 sire mated to five R131317 dams produced progeny segregating for R13R13, R13B17, and B17B17 genotypes. These progeny were injected with 1 mL of 2.5% bovine RBC (BRBC) at 4 and 11 weeks of age to stimulate primary and secondary immune responses, respectively. Serum antibody titers against BRBC seven days post-injection were evaluated by least squares ANOVA. Primary total and mercaptoethanol (ME)-resistant antibodies were significantly lower in R13R13 chickens compared with R13B17 and B17B17 genotypes. R13R13 chickens also had significantly lower secondary total and ME-resistant antibodies than did the R13B17 genotype. The results suggest that genetic differences in R13 homozygotes lower their antibody response to BRBC. This lower response is mitigated by a complementary effect in R13B17 heterozygotes.

Congenic lines homozygous for MHC recombinants (R1R1 = BF24-BG23, R2R2 = BF2-BG23, R4R4 = BF2-BG23, R5R5 = BF21-BG19, R13R13 = BF17-BG23), were inoculated with 20 pock forming units of RSV subgroup C at six weeks of age. Tumor size was scored six times over ten weeks post-inoculation followed by assignment of a tumor profile index (TPI). Tumor growth over time and rank transformed TPI values were analyzed by least squares ANOVA. Tumor size increased over the experimental period in all genotypes except R5R5. R5R5 chickens had significantly lower TPI values compared with R2R2, R4R4 and R13R13 chickens. R1R1 did not differ significantly from any of the other genotypes. The R5 BF21 produced a greater response against RSV tumors than did BF24, BF2 and BF17. Together, the results indicate that the R13 recombination event impacted genes that lowered antibody responses and possibly the antitumor response.

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