RARA and rheumatoid arthritis: In addition, under Th1 or Th17 polarization conditions, the RARα-deficient T cells cultured in vitro did not differentiate into Th1 or Th17 cells, supporting the role of RA in the differentiation of Th1 and Th17 cells, and VitAD mice exhibit significant Th1 and Th17 responses in vivo [53,87,88].