Further molecular complexities of H-2 K- and D-region antigens.

The K and D regions of the H-2 gene complex are highly polymorphic and control cell-surface structures involved in the H-2 restriction of cytotoxic T lymphocytes. Originally it was assumed that each of these regions controlled only one type of antigenic molecule, H-2K and H-2D, respectively. The finding that the D region controls H-2L and H-2M, as well as H-2D, molecules suggests that the system of H-2 antigens is more complicated. We demonstrate here previously unknown H-2 molecules detected by anti-K- and D-region alloantisera in co-capping experiments. Three different types of molecule, distinct from Ia and Qa antigens, are distinguished in the products of the Ddx region, and two in the products of the Dk and Kd regions. Analysis of the antigenic heterogeneity of K- and D-region products may further understanding of the function of these regions in cell-mediated immunity.