Hence, calcitriol exerts a profound effect on CD46-costimulated CD4+T cells, by modulating CD46, CD28, CD25, CTLA-4 and Foxp3 expression, but the modulation of expression of CD25, and in some patients of CD28, is aberrant in MS T cells upon CD46-costimulation. Here, CTLA4 is linked to myeloid sarcoma.