An H‐Deficient Blood with Normal H Transferase Levels

An H-deficient blood is described which, unlike other H-deficient, Bombay and para-Bombay bloods, has normal H transferase levels. In previous examples of Bombay and para-Bombay phenotypes the absence of H transferase has explained the lack of H substrate and therefore the weak A and B antigens which are characteristic of these phenotypes. This explanation obviously does not hold in the case described here and it is proposed that the biochemical block must be further back, either in the enzymes synthesising the oligosaccharide chains or in those making the GDP-fucose substrate for the H and the Le gene-specified fucosyltransferases. Inhibition of the synthesis of Leb substance, as well as H substance, although the saliva of the propositus contains the Le gene-specified transferase, supports this proposition.