CD4 and psoriasis: DHA, a derivative of Nobel Prize-winning artemisinin family, not only is as effective as MTX, a conventional immunosuppressive agent, in ameliorating the acute skin inflammation of psoriasis, but also is better than MTX in alleviating the recurrence of psoriasis via reducing CD8+, but not CD4+, T cell memory, including both CD8+ TCM and CD8+ TRM cells.