A Japanese family with two sisters apparently homozygous for Mk.

Two Japanese sisters with consanguineous parents have M-N- En(a-) Wr(a-b-) S-s-U- red cells and are therefore apparently homozygous for Mk; the third reported family with members of this genotype. The serum of the proposita (ORCMK) contained anti-EnaTS, anti-EnaFR and possibly anti-Wrb, whereas the serum of her MkMk sister contained no atypical antibodies. Total absence of sialoglycoproteins alpha and delta from red cell membranes of an Mk homozygote was demonstrated by lactoperoxidase-catalysed radioiodination of accessible tyrosine residues with subsequent SDS polyacrylamide gel electrophoresis and autoradiography, and by use of a monoclonal antibody directed at the cytoplasmic portion of alpha-sialoglycoprotein.