Technical Articles

IL-21 protein belongs to the IL-2 cytokine superfamily and is primarily produced by CD4-positive T cells. It can also be partially secreted by natural killer T cells, follicular helper T cells, and CD8-positive T cells, with some lymphoid hematopoietic cells capable of producing it in small amounts.

The lack of functional tumor-infiltrating lymphocytes in the tumor microenvironment is a significant reason for the suboptimal efficacy of tumor immunotherapy. Even in tumor tissues rich in tumor-infiltrating lymphocytes, the presence of dysfunctional PD-1-positive Tim-3-positive CD8-positive T cells remains a major indicator of poor prognosis in cancer patients.