Increased association of CD38 with lipid rafts in T cells from patients with systemic lupus erythematosus and in activated normal T cells.

In this study we have determined whether there is a relationship between CD38 expression on T cells, its distribution in different membrane microdomains, and T cell activation in SLE patients. The data show that CD38 expression is augmented in ex vivo CD3+, CD4+, CD8+, and CD25+ SLE T cells, which correlates with its increased insolubility in Brij 98 detergent, and its translocation into lipid rafts. Moreover, SLE T cells show an altered CD4:CD8 ratio, which is due to a decreased proportion of CD4+ T cells and a concomitant increase in the proportion of CD8+ T cells. These data are consistent with the increased CD38 expression and lipid raft formation, and the significant reduction in the CD4:CD8 ratio observed in mitogen-stimulated normal T cells as compared with that in ex vivo untouched normal T cells. Increased expression of CD38 in floating rafts from SLE T cells, or from activated normal T cells may modulate TCR signaling by providing or sequestering signaling molecules to the engaged TCR.