Experimental investigation of roles of STAT4 and SOCS3 in differentiation and cytokine secretion of T helper cells by RNA interference

Abstract

To investigate the roles of signal transducer and activator of transcription 4 (STAT4) and suppressor of cytokine signaling 3 (SOCS3) in differentiation and cytokine secretion of T helper (Th) cells by separate silencing. Th0 cells were induced to differentiate to Th1 or Th2 cells by interleukin 12 (IL-12) or interleukin 4 (IL-4). The mRNAs of STAT4 and SOCS3 were silenced separately by small interfering RNA (siRNA) in Th0, Th1 and Th2 cells and then the lymphocytes cultured in Th1 or Th2 medium with IL-12 or IL-4 for another 48 h before cells and supernatants were collected for the detection of Th1 and Th2 type cytokines by reverse transcriptase polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). By comparing different amounts of cytokines between before and after silencing the target mRNAs, the roles of STAT4 and SOCS3 in the differentiation and cytokine secretion in T helper cells were evaluated. Th1 type cytokine significantly decreased and Th2 type cytokine increased after silencing STAT4 in Th0 and Th1 cells; minimal changes were detected in both Th1 and Th2 type cytokines after silencing SOCS3. STAT4 mediates the IL-12-induced differentiation of T cells to Th1 subset and maintains the cytokine secretion of Th1 cells; STAT4 directly inhibits the development and cytokine secretion of Th2 cells; STAT4 deficiency results in impaired development and cytokines secretion of Th1 cells and the enhanced development and cytokines secretion of Th2 cells. SOCS3 has minimal effects on IL-12 or IL-4 induced differentiation and cytokine secretion of T helper cells.