A novel, soluble homologue of the human IL-10 receptor with preferential expression in placenta.

The cytokine receptor family type 2 (CRF2) comprises receptors for important immunomediators like interferons and interleukin-10 (IL-10). We identified a novel member of this family which represents the first exclusively soluble receptor in this group and was therefore designated as CRF2-soluble 1 (CRF2-s1). The CRF2-s1 gene covers about 28 kb and is located on chromosome 6 in close proximity to the CRF2 members interferon (IFN)-gamma receptor 1 and IL-20 receptor 1. It comprises seven exons and generates two different mRNA splice variants, CRF2-s1-long and CRF2-s1-short. CRF2-s1-long and CRF2-s1-short encode proteins of 263 and 231 amino acids, respectively. A comparison of predicted protein structures led to the postulation that each receptor variants binds a different ligand. Quantitative analysis of human mRNA expression revealed a very restricted pattern for both splice forms. CRF2-s1 turned out to be the first member of this receptor family which was expressed neither in resting nor in stimulated leucocyte populations. CRF2-s1-long was only expressed in placenta, whereas CRF2-s1-short was additionally expressed in human mammary gland and, at a lower level, in skin, spleen, thymus and stomach. The preferential expression of CRF2-s1 in placenta suggests a role for this receptor in establishing and maintaining successful pregnancy.