Objective  To investigate the predictive and diagnostic value of absolute value and function of different lymphocyte subsets in evaluating the risk of early viral infection after kidney transplantation.

  Methods  Ninety-five kidney transplant recipients were enrolled in this prospective observational cohort study, and divided into the stable group (n=77) and infection group (n=18) according to postoperative immune status. Peripheral blood samples were collected for flow cytometry before operation, and 2 weeks, 1 month, 2 months and 6 months after operation. The dynamic changes of the absolute values of CD4⁺T cells, CD8⁺T cells and natural killer (NK) cells were compared between two groups. The function of lymphocyte subsets in two groups was evaluated by detecting the proportion of interferon (IFN)-γ⁺CD4⁺T cells, IFN-γ⁺CD8⁺T cells and IFN-γ⁺NK cells. The value of the absolute values and function of lymphocyte subsets in predicting and diagnosing viral infection in the early stage after kidney transplantation was evaluated.

  Results  During viral infection, the absolute values of CD4⁺T cells, CD8⁺T cells and NK cells in the infection group were at a relatively low level. At 2 months after operation, the absolute values of CD4⁺T cells and NK cells in the infection group were lower than those in the stable group. At 6 months after operation, the absolute values of CD4⁺T cells and CD8⁺T cells in the infection group were significantly lower compared with those in the stable group (all P < 0.05). During viral infection, the proportion of IFN-γ⁺CD4⁺T cells, IFN-γ⁺CD8⁺T cells and IFN-γ⁺NK cells in the infection group were all at a relatively low level, especially that of IFN-γ⁺CD8⁺T cells decreased most significantly. At postoperative 2 months, the proportion of IFN-γ⁺CD8⁺T cells and IFN-γ⁺NK cells in the infection group was significantly higher than those in the stable group. At 6 months after operation, the proportion of IFN-γ⁺CD4⁺T cells and IFN-γ⁺CD8⁺T cells in the infection group was significantly higher than those in the stable group (all P < 0.05). Logistic regression analysis showed that the increasing proportion of IFN-γ⁺CD8⁺T cells and IFN-γ⁺NK cells was correlated with the increasing risk of viral infection at 2 months after operation (both P < 0.05). The receiver operating characteristic (ROC) curve demonstrated that the diagnostic value of absolute values of lymphocyte subsets combined with IFN-γ secretion function for viral infection in the immunocompromised recipients was significantly higher than that of absolute values of lymphocyte subsets alone (P < 0.05).

  Conclusions  Dynamic monitoring of the changes of absolute values and function of lymphocyte subsets provides critical reference value for the prediction, diagnosis and medication guidance of viral infection.