A unique subset of normal murine CD4+ T cells lacking Thy‐1 is expanded in a murine retrovirus‐induced immunodeficiency syndrome, MAIDS

Abstract

Some strains of mice inoculated with LP-BM5 murine leukemia virus (MuLV) develop a syndrome, termed mouse acquired immunodeficiency syndrome (MAIDS), characterized by progressive lymphoproliferation and profound immunodeficiency. LP-BM5 MuLV is a virus mixture that contains ecotropic (eco) and mink cell focus-induced MuLV and a defective genome that is the proximal cause of disease. Flow cytometry analyses of spleen and lymph nodes from susceptible C57BL/6 mice infected with this virus mixture revealed the presence in spleen and peripheral lymph nodes of a previously unrecognized subset of CD4⁺CD3⁺ T cells that are Thy-1⁻. The frequency of these cells increased with progression of disease, eventually comprising between 30% and 50% of all CD4⁺ cells. Infection of A/J mice, a strain which is genetically resistant to development of MAIDS, did not induce an increase of this T cell population, indicating that infection with the virus mixture was insufficient to induce its proliferation. A central role for the defective virus in this process was suggested by the finding that C57BL/6 mice infected with LP-BM5 eco alone did not have increased frequencies of Thy-1⁻CD4⁺ cells in spleen. Studies of spleen and peripheral lymph node cells from normal mice demonstrated the presence of Thy-1⁻CD4⁺ cells at frequencies of 1%–2%. Studies using two anti-T cell monoclonal antibodies, SM6C10 and SM3G11, that define four CD4⁺ subsets showed that Thy-1⁻CD4⁺ T cells from normal and infected mice were present only in the 6C10⁻ subsets.