Given that IL4i1 expression is often associated with tumor-associated myeloid cells (Ramspott et al., 2018), we speculate that especially in low-perfused tissue environments, such as found in solid tumors, local concentrations of IL4i1 can reach much higher levels, attaining a ng/ml range in which we found IL4i1 to mediate its protective effects. This evidence concerns the gene IL4I1 and neoplasm.