Abstract
Background: As key regulatory cells, the impact of follicular regulatory T (Tfr) cells, whose function is regulated by V-domain Ig suppressor of T cell activation (VISTA), on downstream immune cells remains unclear. These cellular-level regulatory mechanisms are closely associated with the development of immune escape in ovarian cancer, a disease characterized by severe effector immune cell dysfunction in the tumor microenvironment. This study aims to elucidate the regulatory effects of VISTA+ Tfr cells on the functions of CD8+ T cells, CD4+CD25- T cells, and B cells, and to reveal their significance in the immune escape of ovarian cancer. Methods: VISTA-overexpressing and silenced Tfr cell models were constructed in vitro. Through co-culture experiments, CFSE proliferation assays, ELISA, and flow cytometry were employed to investigate the effects of VISTA+ Tfr cells on CD8+ T cell proliferation, effector cytokine secretion, and activation status; their regulation of CD4+CD25- T cell proliferation, cytokine secretion, and Th cell differentiation; and their impact on B cell proliferation and antibody secretion. Results: VISTA+ Tfr cells significantly inhibited CD8+ T cell proliferation, secretion of effector cytokines (IL-2, IFN-γ), and expression of the activation marker CD69, while upregulating their exhaustion molecules (PD-1, CTLA-4). They skewed the differentiation of CD4+CD25- T cells toward a Th2 phenotype and suppressed Th1 and Th17 cell differentiation. Furthermore, they specifically inhibited IgE secretion by B cells, with no significant effect on other antibodies. Conclusion: VISTA+ Tfr cells multi-dimensionally suppress the function of effector immune cells, providing experimental evidence for the potential role of VISTA-targeted strategies in improving anti-tumor immune responses in ovarian cancer.