To further elucidate the mechanism by which FAP+CAFs and IL-31 mediate the polarization of naive CD4+ T cells into Th2 cells during immune evasion in gastric cancer, CD8+ T cells isolated from healthy donor peripheral blood mononuclear cells (PBMCs) were co-cultured either with FAP+CAFs alone or with both FAP+CAFs and naive CD4+ T cells. Here, FAP is linked to gastric cancer.