IL7 and rheumatoid arthritis: We had already demonstrated a direct correlation between in vivo levels of circulating IL-7 and the functional capacity of the thymus [10] and showed that peripheral blood mononuclear cells (PBMCs) from RA patients in CR exhibited increased responsiveness to phyto-haemagglutinin (PHA) in vitro, in direct relation to their in vivo exposure to IL-7 [15].