Mouse Ia antigens are receptors for lactate dehydrogenase virus

Infection of mice with lactate dehydrogenase virus (LDV) leads to elevation of plasma lactate dehydrogenase, lifelong viraemia and perturbations of cell-mediated and humoral immune responses. The virus replicates exclusively in a restricted set of macrophages, but the basis for restricted cell susceptibility is unknown. By immunofluorescence techniques we have found that the per cent infected was the same as the per cent expressing antigens encoded by the I region of the major histocompatibility complex (Ia). Infection of CBA strain I-A+ peritoneal macrophages was blocked when cells were treated simultaneously with monoclonal antibody to I-A and I-E, but not with either antibody separately. LDV infectivity was inactivated when virus was treated with purified rat glycoprotein homologous to mouse I-A and I-E antigens. These results indicate that the receptors for LDV are I-A and I-E antigens. Selective infection of Ia-positive macrophages may have an important effect on the immunological capability of infected mice.