The human blood cell that had an factor in common with the turtle blood cell was discovered (in Mr. Wakatsuki), and this common factor was discovered (in Mr. Wakatsuki), and this common factor was named Wk factor.
The Wk factor proved to be an entity entirely independent of the known heterogenetic antigens such as Forssman's antigen, Eisler-Kagatani's antigen, Schiff-Adelsberger's antigen and Castaneda's X antigen.
Of Mr. Wk's family, his younger sister and two of his children were Wk positive (+): thus, it was clear that the Wk factor had been inherited.
From this phenomenon, the Wk factor may be said to be one of the human blood factors.
The occurrence of the Wk (+) type in man has hitherto been limited to Mr. Wk's family, but has not been found in any other family.
In view of these facts, the Wk factor appears to be a kind of family antigen.
