CRIPTO3 and neoplasm: Given the abundant expression of CR3 in NK cells, negative regulatory roles of iC3b/CR3 axis in other immune cells and the association of iC3b with tumor progression, we hypothesized that iC3b/CR3 signaling is an important negative regulator of NK cell function, which may have negative impact on tumor surveillance and hinder the efficiency of NK-based and antibody-based therapies.