Sources of HLA typing sera.

Antibodies to antigens of the HLA system are formed by a proportion of women during a pregnancy and sometimes after blood transfusion. The gestational antibodies are of no significance to the pregnancy and in most cases they are thought to disappear from the serum a few weeks after termination of the pregnancy. They are, however, of great value as HLA typing reagents and most tissue typing laboratories (including our own) rely heavily on pregnancy sera as their source of HLA antisera. Blood samples from many mothers during their pregnancies are sent to the Northern Ireland Blood Transfusion Service for red cell antibody screening and aliquots of these sera are also examined for HLA antibodies. When a serum is found to contain a monospecific antibody of potential value for tissue typing, the patient and/or her family doctor are contacted and arrangements are made to take a further 50 ml sample of blood. This serum is sufficient for our own needs but in order to facilitate the interchange of sera with other laboratories both in the United Kingdom and abroad larger volumes of sera are necessary. It is inappropriate to ask for a full standard donation of blood from a mother a short time before or after the end of a pregnancy. Large volumes of serum can be obtained by plasmapheresis, a procedure which entails no loss of red cells by the patient, but because of the time involved it is often inconvenient for the mother of a new baby to attend hospital (or the transfusion service building) to give plasma by this means. "We have therefore considered a different approach for obtaining large volume supplies of HLA typing sera. In some women, HLA antibodies may persist for years after pregnancy (Tongio, Berrebi and Mayer, 1973) and therefore a proportion of female blood donors might be expected to have these persistent and stable antibodies. It would not be difficult to obtain 'dry bottle' donations from selected regular blood donors at their next visit to the transfusion centre. With a view to obtaining HLA typing sera in this way we screened blood samples from a group of female blood donors. This paper reports our findings.