C1QBP and neoplasm: The C1q–gC1qR interaction in the TME appears to mimic that of the PD-1/PD-L1 interaction with the cancer cell surface-expressed C1q serving the role of PD-L1 and the immune cell-expressed gC1qR serving the role of PD-1, thereby attenuating the T-cell signals directed at attacking the tumor cells19.