My donor card says O Ccee rhesus positive as donor – rhesus neg. as a receiver. Can I only give to positive?

Answer

If you are rhesus positive, this means that D antigens (specific proteins) are present on your red blood cells (RBC). If this rhesus positive blood is given to a person who is rhesus negative, the recipient will form antibodies against the D antigen on the RBC, because the recipient’s body does not recognize this antigen because the recipient does not have this antigen itself. Those antibodies can then destroy rhesus positive blood if this person were to receive rhesus positive blood for the second time.

Since you are rhesus positive as a giver and rhesus negative as a recipient, this means that you probably have incomplete D antigens on the RBC.

So if your blood were given to a person who is rhesus negative, the recipient will form antibodies to destroy rhesus positive blood cells. So your blood is best given to people who are rhesus positive who won’t form antibodies. If you need blood yourself, they will opt to give rhesus negative blood. If you were to receive rhesus positive blood, your body may not recognize part of the D antigen on the RBC you received, because that piece of D antigen is missing from your RBC. As a result, your body will produce antibodies against the rhesus positive RBC. If you then received rhesus positive blood for the second time, the RBCs received would be destroyed by those antibodies. This is why you as a recipient are considered rhesus negative.