In order to explore whether T cells alter during the generation and maturation in SLE patients, we researched the composition of immune cells in the thymus using MRL/lpr mice as a model, as results showed, in the thymus of MRL/lpr mice, the proportion of double positive cells (CD8+CD4+) decreased and the CD4 single positive cells as well as PD1+CXCR5+ Tfh cells increased. The gene discussed is PDCD1; the disease is systemic lupus erythematosus.