Expansion of unusual CD4(+) T cells with an intermediate T cell receptor intensity in autoimmune BXSB mice and their T cell receptor repertoire

CD4(+)T cells accumulate in autoimmune male BXSB mice with age. In the pres ent study, we carried out a detailed T cell receptor (TCR) repertoire analy sis of MNC (mononuclear cells) of the liver, spleen and lymph nods in these mice. Expanded MNC consisted mainly of IL-2 receptor beta chain (IL-2R bet a)(+) CD4(+)T cells with intermediate TCR intensity (TCRint) that was lower than the high TCR intensity (TCRhi) of:regular T cells. Although the IL-2R beta(+) CD4(+)TCR(int) cells in normal mice or female BXSB mice are consid ered to be natural killer T (NKT) cells and mainly express V alpha 14 gene products coupled with either V beta 8 or V beta 7 gene products, IL-2R beta (+) CD4(+)TCR(int) cells of aged male BXSB mice were V alpha 14(-) and the frequency of the V beta 8 T cells was much lower that of IL-2R beta(+) TCRi nt cells of female BXSB mice. Furthermore, the proportions of V beta 3, V b eta 6 and V beta 7 T cells increased in the IL-2R beta(+) TCRint cells more than in the TCRhi cells of aged BXSB mice. On the other hand, the IL-12 in jected liver MNC and splenocytes from male BXSB mice showed much greater NK activities than those from female mice and the IL-2R beta(+) CD4(+)TCR(int ) cells were found to be responsible for the NK activity of liver MNC. Thes e findings suggest that although IL-2R beta(+) CD4(+)TCR(int) cells in male BXSB mice are different from either regular NKT cells or TCRhi cells, they are nevertheless still functionally closer to NKT cells than to regular TC Rhi cells.