Abstract: 【abstract】Objective To investigate T lymphocyte function and prevalence of microangiopathy in Type 2 diabetes mellitus patients with black patches on pre-tibia. Methods Percentage of CD3+ to total lymphocytes was measured through flow cytometry, so were the percentages of CD4+ and CD8+ to T lymphocytes. Results (1) There was no significance between black-patch group and non-black-patch group in the percentage of CD3+ to total lymphocytes（P＞0.05）; The percentage of CD8+ to T lymphocytes in the black-patch group was significantly lower than that in the non-black-patch group （P＜0.01）; Both of the the percentage of CD4+ and the ratio of CD4+/CD8+ in the black-patch group were significantly higher than those in the non-black-patche group（P＜0.01）.(2) Incidence of chronic complications, especially microangiopathy, in the black-patche group was significantly higher than that in the non-black-patch group （P＜0.05）Conclusion Black patches on pre-tibia could be a dermatic sign of immune disorder and microangiopathy in type 2 diabetes mellitus. Black patches and other microangiopathy in type 2 diabetes mellitus could be related to disorder of cyto-immune function.

Key words: Type 2 diabetes mellitus, Black patches on pre-tibia, CD3+, CD4+, CD8+, CD4+/CD8+, T cell