If an antigen encounters a T cell, the T cell can multiply rapidly. These activated T cells engulf and digest the antigen, such as a cancer cell, virus, fungus, or bacterium. T cells also react to foreign tissues, such as skin grafts and transplanted organs.

如果抗原遇到T细胞，T细胞可迅速繁殖。这些活化的T细胞吞噬并消化抗原，例如癌细胞，病毒，真菌或细菌。 T细胞也会对外来组织起反应，例如皮肤移植物和移植器官。