The expression patterns of the inhibitory receptors PD-1 and TIGIT on CD4+ and CD8+T lymphocytes at different stages of differentiation

T lymphocytes are a highly diverse group of cells that play a pivotal role in the adaptive immune response. The T cell population consists of two subsets: CD4+T-helper cells and CD8+ cytotoxic T lymphocytes, each comprising cells with varying functionality and maturity levels. Inhibitory receptors such as PD-1 and TIGIT tightly regulate T lymphocyte functions to maintain immune homeostasis. However, the presence of inhibitory receptors on T cells is also associated with exhaustion. The specific characteristics of inhibitory receptor expression on CD4+ and CD8+T lymphocyte subsets are not fully understood. This study aimed to assess the expression of inhibitory receptors PD-1 and TIGIT on different subsets of CD4+ and CD8+T lymphocytes in healthy individuals. The study involved 10 relatively healthy volunteers, averaging 43 years. T lymphocytes subsets were identified using flow cytometry. CD4+ and CD8+T cells were classified as naive (CD45R0-CCR7+), central memory (CD45R0+CCR7+), effector memory (CD45R0+CCR7-), or terminally differentiated effectors (CD45R0-CCR7-) followed by analysis of PD-1 and TIGIT expression. The study showed that the expression of suppressor molecules PD-1 and TIGIT on T lymphocytes in healthy individuals is closely linked to their differentiation stage. The presence of cells carrying PD-1 and TIGIT receptors was significantly lower in naive T lymphocytes compared to more mature subsets (p 0.05). Affiliation with CD4+ or CD8+T cells also significantly influenced the nature of inhibitory receptor expression. CD8+T lymphocytes had more TIGIT-positive elements than CD4+T cells (p 0.01). Moreover, unlike PD-1, TIGIT was found on most memory and terminally differentiated effector CD8+T lymphocytes. These findings improve our understanding of how inhibitory receptors regulate T cell functions and emphasize the need to reconsider how we interpret data in the context of T lymphocyte exhaustion.