We also associated reduced levels of interleukin-7 (IL-7) in the bone marrow, thymus and blood with profound and persistent lymphopenia in RA post chemotherapy [10,15–17] and showed normalization of circulating IL-7 levels in approximately 50% of RA patients in clinical remission (CR) defined by disease activity score (DAS) <2.6 [12]. Here, IL7 is linked to lymphopenia.