A possible null phenotype in the Cromer blood group complex.

The red blood cells of a Japanese man failed to react with anti-Cra sera and with three Cromer-related sera, B.P., G.T., and K.T.O. His serum reacted with all red blood cells tested except his own. This phenotype, which may represent a null phenotype in the Cromer complex, supports the suggestion that the phenotypes of B.P., G.T., and K.T.O. are Cromer related.