The Raph blood group system consists of only one antigen. It has the unique distinction in that more is know about this antigen (and system) using monoclonal antibodies than could be deduced through the use of human source antibody. While the human source antibody was detected first in a patient from whom the name is derived, most of the serological information was collected from tests with the monoclonal antibody (MER2) of a similar specificity. The human source antibody was difficult to work with, whereas the monoclonal antibody was more readily available and contained no other contaminating antibodies.

The Raph antigen is found in 92% of the English population and is a product of a gene located on the short arm of chromosome 11 (11p15). The expression of the antigen appears to be quantitatively variable amongst the Raph+ individuals. The protein structure that carries the Raph antigen is unknown at the present time.

Interestingly, the three presently known examples of human antibody were produced in Jews of India origin but now living in Israel (a set of sibs and the other unrelated). All three individuals are on renal dialysis because of kidney failure. Is this merely coincidental or could this possibly suggest the Raph is located on other tissue and this may have some significance with the original antibody producers disease? The monoclonal antibodies that have been produced were stimulated in a mouse using a human small cell carcinoma line, therefore, it is possible that Raph could be located on other tissue.

The importance of Raph in transfusion medicine appears to be nonexistent in that the above three individuals have received Raph+ transfusions and have not had transfusion reactions.