Molecular events in the processing of avidin by antigen-presenting cells (APC)

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Abstract
The differences between the immune response (Ir) phenotypes ofH-2 gene-controlled high- and low-responder mice have been attributed to events occurring at the interaction between antigen-presenting cells (APC) and lymphocytes. To investigate this interaction we undertook a study of molecular events in the processing of avidin, a molecule whose uniquely strong affinity for binding to biotin renders it traceable at very low concentrations, and a molecule to which the T-lymphocyte immune response is controlled byIr genes. In this paper we describe the generation of processed avidin by APC and characterize it biochemically and,immunologically. We found that APC ofH-2 genetically high-and low-responder mice were indistinguishable in their capacity to generate immunogenic processed avidin (PA). Immunogenic PA differed from native avidin in size and carbohydrate moieties, but preserved its capacity to bind biotin, and was 1000-fold more efficient than NA as an immunogen for primed T lymphocytes. Primed T lymphocytes appeard to recognize PA that was conformationally intact. Highly immunogenic PA was notH-2 restricted. Thus, differences in the Ir phenotype of the response to avidin could not be attributed to determinant selection by APC.