This review surveys soluble Folate Receptors (FOLRs) in humans. FOLR1 and FOLR2 are equipped with cellular glycosylphosphatidylinositol (GPI) anchors. FOLR1 is secreted from epithelia with or without a micelle-encapsulated GPI-anchor into milk and other body fluids/secretions, e.g. semen where its interaction with spermatozoa indicates a role in male fertility. FOLR1 and FOLR2 serve as serum biomarkers of various diseases. FOLR3 possesses no GPI-anchor and originates from secretory granules of neutrophil granulocytes; its concentration in serum correlates to the FOLR3 content in leukocytes and rises with increased leukocyte counts (infection, malignancy and pregnancy). FOLR3 exerts anti-microbial and anti-tumor effects by depriving bacteria and tumor cells of natural folates. Megalin receptors mediate reabsorption of ultrafiltered folate-bound FOLR into cells of proximal kidney tubules and of folate-bound FOLR uptake in growing embryos. Megalin receptors overexpressed in malignant tumors could be suitable therapeutic targets for folate-conjugated cytotoxic agents utilizing soluble FOLRs as vectors.

这篇评论调查了人类中的可溶性叶酸受体（FOLR）。FOLR1和FOLR2配备了细胞糖基磷脂酰肌醇（GPI）锚。FOLR1是在有或没有胶束封装的GPI锚的情况下从上皮分泌到牛奶和其他体液/分泌物中的，例如精液，它与精子的相互作用表明其在男性生殖力中的作用。FOLR1和FOLR2充当各种疾病的血清生物标志物。FOLR3没有GPI锚，起源于嗜中性粒细胞的分泌颗粒。其在血清中的浓度与白细胞中的FOLR3含量相关，并随着白细胞计数（感染，恶性肿瘤和妊娠）的增加而升高。FOLR3通过剥夺细菌和肿瘤细胞中的天然叶酸来发挥抗微生物和抗肿瘤作用。Megalin受体介导超滤叶酸结合的FOLR进入近端肾小管细胞的重吸收以及叶酸结合的FOLR在生长中的胚胎中的吸收。在恶性肿瘤中过表达的Megalin受体可能是利用可溶性FOLRs作为载体的叶酸偶联细胞毒剂的合适治疗靶标。