Objective:To investigate the correlation between CD4+T cell division and surface molecule expression or cytokine production after stimulation with antigen.Methods:Isolation of CD4+T cells from spleens and lymph nodes of OVA-T cell-receptor transgenic mouse (TCR-Tg ). After stimulation with OVA peptide antigen in the presence of antigen-presenting cells, CD4+T cell division, surface molecule expression and intracellular cytokine production are determined in flow cytometry.Results:CD4+T cells are divided 1-5 times after stimulation for 3 days with antigen. The cell division is associated with both up- and down-regulation of surface molecules such as CD25, CD44, CD62L and CD69 and of cytokines such as IFN-?, IL-4 and IL-10.IL-12 promotes cell division and enhances IFN-? but inhibits IL-4 and IL-10 production.Conclusion:After stimulation with antigen, CD4+T cells are divided in association with the quantitative and qualitative changes of surface molecules and cytokine production.