PDCD1 and colorectal carcinoma: We further analyzed the T follicular helper (Tfh) response, and CD4+PD1+CXCR5+ cells were significantly decreased in adenoma grade II (3.95 vs. 0.63, P = 0.0157), grade III (3.95 vs. 0.26, P = 0.0002), and CRC (3.95 vs. 0.16, P < 0.0001) compared with the control (Figure 6A).