To explore the role of methotrexate (MTX) in regulating the number of regulatory T cells (Treg) and the mRNA expression of transcription factor Foxp3.
 Methods: 1) We analyzed the number of Treg and the mRNA expression of Foxp3 by flow cytometry (FCM) and quantitative real-time PCR (qRT-PCR) respectively in patients with psoriasis vulgaris, patients with psoriasis vulgaris after the 8-week treatment of MTX, and healthy people. 2) BALB/c female mice were smeared with imiquimod (IMQ) cream for 6 days. We recorded the change of the lesion in mice every day. The morphological changes of lesion in mice were evaluated by the psoriasis area and severity index (PASI) and HE staining. 3) The mouse model was randomly divided into a control group and an MTX group. The MTX group was treated with different doses of MTX (38.5 and 77.0 nmol/L) on the third day of this experiment. The morphological changes of lesion in mice were evaluated by PASI and HE staining. We tested the number of Treg and the expression level of Foxp3 mRNA in splenic lymphocytes.
 Results: 1) The number of Treg and the expression level of Foxp3 mRNA were lower in psoriasis vulgaris patients than those in the healthy control group (P<0.05). After 8-week treatment of MTX, the number of Treg was increased (P<0.05) and Foxp3 mRNA level was up-regulated (P<0.01). 2) Typical psoriasis-like skin lesions, such as red scaly skin plaque were found after topical application of IMQ. Both the number of Treg in the splenic lymphocytes of mice and the Foxp3 mRNA level of Treg were reduced by IMQ (P<0.01 and P<0.05). 3) Different doses of MTX for mice showed the ability to improve skin lesion, increase the number of Treg in the spleen of mice and Foxp3 mRNA level in psoriatic dermatitis of mice (P<0.05).
 Conclusion: MTX is able to regulate the number of Treg and Foxp3 mRNA expression in psoriasis.
Adjuvants, Immunologic ; pharmacology ; Aminoquinolines ; pharmacology ; Animals ; Case-Control Studies ; Female ; Forkhead Transcription Factors ; metabolism ; Humans ; Imiquimod ; Immunosuppressive Agents ; administration & dosage ; pharmacology ; Lymphocyte Count ; Methotrexate ; administration & dosage ; pharmacology ; Mice ; Mice, Inbred BALB C ; Psoriasis ; drug therapy ; immunology ; metabolism ; pathology ; RNA, Messenger ; metabolism ; Random Allocation ; Spleen ; cytology ; T-Lymphocytes, Regulatory ; cytology ; drug effects ; metabolism