Peripheral CD4+CD8+ cells are the activated T cells expressed granzyme B (GrB), Foxp3, interleukin 17 (IL-17), at higher levels in Th1/Th2 cytokines

Peripheral CD4+CD8+ T cells have been identified as a T cell subset existing in animals and humans. However, the characterization of CD4+CD8+ T cells, their relationship with T memory (TM), T effector (TE), Th1/Th2, Treg and Th-17, remain unclear. This study was to characterize the CD4+CD8+ T cells. The results from human subjects showed that activated T cells were CD4+CD8+ T cells, comprised CD4hiCD8lo, CD4hiCD8hi and CD4loCD8hi subsets. They expressed CD62Lhi/lo, granzyme B (GrB), CD25, Foxp3, interleukin 17 (IL-17) and the cytokines of both Th1 and Th2, and had cytolytic function. These findings suggested that CD4+CD8+ T cells had over-lap function while they kept diversity, and that T cells could be divided into two major populations: activated and inactivated. Hence, the hypotheses of Th1/Th2, Treg and Th-17 might reflect the positive/negative feedback regulation of immune system. When compared to GrB+CD62Llo T effector (TE) cells, GrB+CD62Lhi T central memory effector (TCME) cells had a quicker response to virus without CD62L loss.