Self-reactivity and the expression of memory markers vary independently in MRL-Mp+/+ and MRL-Mp-lpr/lpr mice.
MRL-Mp-lpr/lpr mice contain phenotypically abnormal populations of T cells, and exhibit an SLE-like autoimmune disease in which autoantibodies are a prominent feature. We analyzed the phenotype and T-cell receptor V beta expression pattern in CD4+ T cells of this mutant mouse strain to detect abnormalities that could explain the autoimmunity. The CD4+ T cells contain two distinct abnormal populations. One of these expresses B220 and HSA, and in these and other respects closely resembles the accumulating CD4-CD8- population. The other expresses a high level of CD44 (Pgp-1), and a high level of the 16A epitope of CD45, and so resembles post-activation T cells. Both of these cell types are exclusive to MRL-Mp-lpr/lpr. We also identified V beta 5- and V beta 11-positive CD4+ T cells, in both MRL-Mp-lpr/lpr and MRL-Mp-+/+ mice. We conclude that autoimmune T cells can be detected in these mice, but that they are not the cause of the accumulation of abnormal CD4+ and CD4-CD8- cells.