ABCB1 and rheumatoid arthritis: It is interesting, however, that these changes are to be found in lymphocytes from peripheral blood and not exclusively located in the synovia, being that, although peripheral blood lymphocytes from patients with RA do not coincide within a general activation state, there have been reports of alterations in their proliferation and differentiation rate, with a decrease of naïve CD4 cells [31], and certain memory T-lymphocytes populations show an increase in the expression of ABCB1, whose functional meaning has not yet been ascertained [32].