Isoform A binds to IL-18 and inhibits its activity. Functions as an inhibitor of the early TH1 cytokine response. Strongly expressed in heart, lung, placenta and spleen. N- and O-glycosylated. O-glycosylated with core 1-like and core 2-like glycans. O-glycan heterogeneity at Ser-53: HexHexNAc (major) and Hex2HexNAc2 (minor). N-glycan heterogeneity at Asn-103: Hex5HexNAc4 (minor), dHex1Hex5HexNAc4 (major) and Hex6HexNAc5 (minor); N-glycan at Asn-147: dHex1Hex5HexNAc4. Disease susceptibility may be associated with variants affecting the gene represented in this entry. Truncated N-terminus. Truncated N-terminus. Intron retention. Truncated N-terminus. Truncated N-terminus. Intron retention. Truncated N-terminus.