Influence of the chicken major histocompatibility complex on the development of Escherichia coli derived cellulitis

A common subcutaneous infection in chickens is caused by Escherichia coli (E. coli) and is known as cellulitis. Though not fatal this affliction costs the broiler industry millions due to carcass condemnation at the processing plant. One way to control E. coli in a commercial broiler operation is by administering antibiotics to the flock, however due to governmental as well as consumer pressures this practice will become forbidden. It was hypothesized that if the bird's immune system were able to control this infection it would preclude the need for antibiotics in controlling this problem. A key component of the chicken immune system is the major histocompatibility complex (MHC or B). The MHC is important for orchestrating the interactions between antigen presenting cells and lymphocytes within an organism.; Little is known of the role chicken MHC plays in preventing bacterial infections. Given that the MHC is a major factor influencing immune response, it is hypothesized that different MHC types may produce different incidences of cellulitis and/or influence the severity of the cellulitis lesion. In order to determine this a series of experiments were performed to determine the effect chicken MHC has on E. coli induced cellulitis. Specifically, by looking at different chicken lines and E. coli from different origins. Additionally immunological parameters were also examined to determine if either cellular or humoral immunity is the predominant immunological branch responsible for removing the E. coli.; These experiments indicate that the MHC genotype B13 conferred relative resistance to most strains of cellulitis causing E. coli, while B21/B21 was susceptible. This MHC difference was seen in both broiler and leghorn strain chickens, which implies that it is MHC or some gene(s) that are closely linked to the MHC that are responsible for this pattern. Interestingly, though, is that this MHC effect seemed specific to only certain E. coli isolates. Additionally, antibodies, specifically IgG, control the prevention of cellulitis development.; This research could financially benefit the broiler industry and also could be used to develop a vaccine to prevent cellulitis caused by E. coli.