Comparison of immune response of inducible nitric oxide synthesis (iNOS) hyper and hypo-responsive genotypes of chickens

Abstract: Cornell K-strain (B B) is hyper and GB1 (B B) and GB2 (B B) are hypo responder chicken15 15 13 13 6 6 genotypes for iNOS gene expression and activity. Two trials were conducted to compare these lines for immune parameters. For mononuclear phagocytic function quantification, 5 chickens per group were injected i.v. with Black India Ink at a rate of 1 mL/kg body weight (BW) at 4 wk. Blood samples were drawn and optical density measured at 640 nm on plate reader. K-strain was significantly better in clearing carbon (P = 0.04) than the GB1 and GB2 chickens at 10 min post i.v. injection. Lymphoproliferation was measured in vitro by incubating 0.2 x 10 peripheral blood leukocytes with 25 µg Concanavalin A. K-strain chicks had the highest6 lymphoproliferation index than the GB1 and GB2. On the contrary, K-strain chicks had a weaker PHAP-mediated toe-web swelling response as compared with the GB1 and GB2 chicks. No differences were observed between genotypes for the total or IgG anti-SRBC antibodies in primary or secondary immunization response (one trial). However, K-strain exhibited greater persistence (P < 0.05) of IgM levels than GB2 chicks during the decline phase of the booster response. While K chicks had heavier BW (P < 0.01), they had smallest bursal, thymic and splenic weights (relative to BW) vs. GB1 and GB2 in both trials. These findings show that the iNOS hyper responder K-strain chickens also perform better for monocyte/macrophage, T-lymphocyte and perhaps even B-lymphocyte functions even though their lymphoid organ growth lagged behind the iNOS hyporesponder (GB1 and GB2) genotypes