An antibody that recognizes a determinant common to S and s-bearing sialoglycoproteins.

We describe an antibody, made by an individual of the phenotype M+, N+, S+, s+, U+, that reacted only with ficin or papain-treated red blood cells, and that initially appeared to have anti-S specificity. However, further studies revealed that the antibody, which did not have anti-U specificity, recognized a determinant present on S+, s-, U+, and S-, s+, U+, but missing from S-, s-, U-, and S-, s-, U+, red blood cells. The specificity of this antibody is discussed in terms of current knowledge of the structure of the Ss sialoglycoprotein.