Role of Ia.W39 in the interaction of antigen‐presenting cells with T and B lymphocytes

Abstract

Ia.W39 is a B cell differentiation antigen whose membrane expression is controlled by the xid gene. Analogous to its B cell expression, Ia.W39 is also present on a subset of Ia+ macrophages, indicating heterogeneity within that cell population. The Ir gene(s) for the antigenic determinants on the A chain loop of beef insulin maps to the I-Ab subregion of the H-2 complex and, as previously reported, is associated with the private specificity Ia.W39. Depletion of Ia.W39+ macrophages eliminates their capacity to present beef insulin to immune T cells, the presentation of the multideterminant antigen trinitrophenylated ovalbumin is reduced < 50%. H-2b mice lacking Ia.W39+ cells are unable to make a secondary in vivo IgG plaque-forming cell (PFC) response to beef insulin, the primary IgG PFC response is not dependent on Ia.W39. No shift in the kinetics of the response, nor development of suppressor T cells was detected in Ia.W39- mice, which would explain their apparent nonresponsiveness to beef insulin after boosting with this antigen. These results may reflect a difference in the Ir gene control acting at the primary vs. secondary response level.