The Effect of the Changes in T Lymphocyte Subsets and IL-2 During Different Stages of Pregnancy and Puerperium on the Carcinogenesis of TA2 Mice

Abstract

Objective: To observe the changes in T lymphocyte subsets and IL-2 during different stages of pregnancy and puerperium in TA2 mice, and to investigate the possible influences of pregnancy and puerperium on the cellular immune function and the carcinogenesis of TA2 mice.Methods: The TA2 mice were divided into 9 groups including normal group, spontaneous breast cancer group, mice on the 5th day of pregnancy, 10th day of gestation, 20th day of gestation and mice on the 1st, 7th, 14th, and 21st days of postpartum.The percentages of CD3+, CD4+ and CD8+ T cell subsets in mice spleen were examined by flow cytometry.The ratio of CD4+ to CD8+ T cell subsets (CD4/CD8) was caculated, and IL-2 in mice serum was determined by ELISA.Results: Compared with that in the normal group, the percentage of CD3 + T cell subsets was decreased during every stage of pregnancy and postpartum (P0.01) and reached the lowest level on the 10th day of pregnancy (P0.01).The percentages of CD4+ T cell subsets and CD4/CD8 were decreased to the lowest in 20th day of pregnancy group (P0.01 and 0.05), while the percentage of CD8+ T cell subsets was increased to the highest (P0.01).Compared with that in the spontaneous breast cancer group, the percentage of CD3+ T cell subsets in other groups (except in the 10th days of pregnancy group) was higher.There was no significant difference in the percentages of CD4+ and CD8+T cell subsets and CD4/CD8 ratio between the spontaneous breast cancer group and other groups.IL-2 level was decreased during pregnancy, and there was a significant difference between the 10th day of pregnancy group and the 20th day of pregnancy group (P0.05).Although IL-2 was increased on the 1st day after delivery, it was decreased gradually in the 7th, 14th, and 21st days of postpartum groups, significantly lower than that in the normal group (P0.01) and similar to that of the spontaneous breast cancer group (P0.01).Conclusion: Pregnancy and delivery affect the distribution of T cell subsets and the level of IL-2 to some degree, which could suppress cellular immune function and is one of the reasons of carcinogenesis of mammary gland in TA2 mice.