C5AR1 and neoplasm: A possible explanation of our observation is that pAb mediated CDC against target cells, releasing tumor-derived antigens and resulting in the local production of C3a and C5a anaphylatoxins that bind their respective GPCRs, C3aR and C5aR, expressed on T cells and antigen-presenting cells, and this binding drives T cell differentiation, expansion, and survival (46).