Multiple mechanisms regulate the expression of murine immune response genes

The immune response antigens (la antigens) are heterodimeric cell-surface glycoproteins that regulate lymphocyte and macrophage interactions leading to the production of antibody against foreign antigens. The class II genes in the I region of the murine major histocompatibility complex encode the α and β chains of the two known la antigens, I-A and I-E. Molecular cloning of the I region led to the discovery of three DNA regions, Aβ2, ψAβ3, and Eβ2, which share some nucleotide homology with the classical class II β genes. In this report we present evidence that Aβ2 is transcribed in spleen and in a cultured B cell hybridoma. Aβ2 mRNA is also found on membrane-bound polysomes, suggesting that it is translated. In contrast to the classical I region genes, Aβ2 transcripts are not induced in macrophage cells by γ-interferon (γ-IFN). This difference in sensitivity to γ-IFN suggests that B cells and macrophages regulate the expression of the class II genes by distinct mechanisms.