Several well-known quantitative mathematical models which describe division/death processes of activated CD4 positive T cells can be equivalently reformulated by a system of delay equations. Based on this finding, I show some stochastic simulation results for cell division, death and differentiation of CD4 positive T cells. Our method can be used to investigate the dynamics of cell population growth both qualitatively and quantitatively. In the workshop, I would like to discuss possibility of contribution of our method to experimental studies on CD4 positive T cell division and differentiation.