TPH1 and rheumatoid arthritis: In T cell subpopulations, a significant increase in cTh1 cells, cTfh1 cells, and Tph cells and significant decrease in cTh17 cells, cTh17.1 cells, and CD8+ Treg cells was observed in the patients with RA from Karuizawa compared with those of Tsukuba after IPW adjustment.