Compartmentalization of MHC class II gene expression in transgenic mice.

A set of transgenic mouse lines carrying Ek alpha genes with promoter region deletions was created in an attempt to compartmentalize MHC class II gene expression. Fine immunohistological analyses established that one transgenic line is essentially devoid of E complex in the thymic cortex, another displays almost no E in the thymic medulla or on peripheral macrophages, and two lines display no E on greater than 98% of B cells. We have assayed these mice for immune function: E-dependent tolerance, antigen presentation, T cell priming, and antibody response. Certain of the findings are difficult to reconcile with currently popular hypotheses, e.g., tolerance induction to E molecules in the virtual absence of E complex in the thymic medulla and efficient antibody responses to E-restricted antigens when almost all B cells are E-.