Although IL-23 induces apoptosis of self-reactive thymocytes in thymic negative selection [55], we observed that serum levels of IL-23 correlated negatively with apoptosis of PBMCs isolated from RA patients, indicating a possible link between the production of IL-23 by monocytes/macrophages and resistance to apoptosis of PBMCs. The gene discussed is IL23A; the disease is rheumatoid arthritis.