Mechanism of CD138 expression in CD3+ T cells of MRL/lpr mice
Current research on CD138+ T cells remains limited, and little is known about the mechanism underlying the CD138 expression in CD3+ T cells. A recent study revealed that CD138+ T cells accumulated in MRL/lpr mice, but not in non-lupus prone mice 14. Furthermore, CD3+ T cells in MRL/lpr mice have been shown to exhibit significantly defective activation and proliferation, compared with the cells in MRL/MPJ mice (unpublished data by Tianhong Xie et al.). Importantly, previous research has demonstrated CD138+ T cells exhibit significantly lower proliferation and activation in MRL/lpr mice, compared with CD3+CD138- T cells 14. The activation levels of CD3+ T and CD138+ T cells have also been shown to be inversely correlated with the frequency of CD138+ T cells in splenocytes (unpublished data by Tianhong Xie et al.). It has also been suggested that the mechanistic target of rapamycin controls the expression of CD138 in T cells. Furthermore, rapamycin has been reported to significantly reduce the expression of CD138 and the frequency of CD138+ T cells14. However, an in vitro effort to decrease the frequency of CD138+ cells in CD3+ T cells with rapamycin treatment was unsuccessful. On the contrary, phorbol 12-myristate 13-acetate and Ionomycin treatments were found to significantly decrease the frequency of CD138+ cells in CD3+ T cells and induce the specific apoptosis of CD138+ T cells (unpublished data by Tianhong Xie et al.). This suggests that the defective activation of CD3+ T cells in MRL/lpr mice probably leads to the expression of CD138 in CD3+ T cells.