CD4 and arthritic joint disease: To assess the effect of PLGA‐ATRA MP on Treg stability, CD4+tdTom+ T cells after arthritis induction were compared between littermates that received IA PLGA‐ATRA MP or PLGA‐Blank MP, analyzing the pooled draining lymph nodes (inguinal and popliteal), pooled ankles, and the spleen.