Expression of CD138 prevents T cell apoptosis and contributes to accumulation of DN T cells
DN T cells are a subset of T cells that are CD3 and B220 positive and are negative for both CD4 and CD8. DN T cells have been found to accumulate in the peripheral blood of SLE patients and in an SLE murine model 9-11. They were found to account for <7% in the T cells of healthy mice6, and resulted in profound lymphadenopathy in an SLE murine model10, 31. DN T cells have been shown to express activation-associated antigens, such as CD44, Ly-6C, CD138, and CD69 13, 26, 32-34. Interestingly, it has recently been shown that a majority of DN T cells express high levels of CD138 12-14. Moreover, the expression of CD138 in T cells has been demonstrated to significantly prevent the apoptosis of T cells 14. Thus, it appears that the expression of CD138 contributes to the accumulation of DN T cells in lupus mice by decreasing the number of apoptotic DN T cells (Figure 2). However, the underlying mechanism for the expression of CD138 in CD3+ T cells remains undeciphered.