A shared B-T cell phenotype in autoimmune mice bearing the lpr gene.

MRL-lpr mice and MRL-+/+ mice are identical except for the presence of an autosomal recessive lymphoproliferation gene (designated lpr) in the former. Mice bearing the lpr gene develop autoimmune and lymphoproliferative abnormalities. An antigenic marker designated 14D10, characteristically expressed on the surface of Lyt-2+ T cells and B cells of normal mice, is expressed in unusually high levels on Thy-1+ cells of lpr mice which are Lyt-2-. In younger lpr animals, 14D10+ cells are a minor subpopulation of Ia+ cells which, when expanded in diseased animals, continue to express Ia. 14D10+ cells from lpr mice are elevated in fetal spleen and adult bone marrow (BM) but are absent on pre-B cells in the BM. Medullary thymocytes of lpr mice are enriched in 14D10+ cells compared to congenic (+/+) controls. Although 14D10 appears to be present on the activated, proliferating T-cell population, coculture of lpr cells with IL-2 leads to minimal proliferation. 14D10+ Lyt-2- T cells can be isolated from normal spleens, indicating the lpr gene may be responsible for the disregulated proliferation of a minor cell subset. The functional significance of this molecular complex is still undetermined.