Case study: Use of A2 and donor red blood cells for anti ABO a titer

Abstract

ABO incompatibility (ABOi) is no longer an absolute contraindication for kidney transplantation. Recipients who are either blood group O or B have successfully received kidney transplants from donors who are blood group A, as long as their titer against the donor A antigen is low. Although the predominant A antigen subtype in the population is A1, less than 20% of blood group A individuals are of other subtypes, with weaker antigen expression, A2 being the most common of these. Accurate quantification of the amount of Anti A antibody titer in the recipient against the intended donor is important to determine compatibility for ABOi transplants. A review of the literature demonstrated that there is a high degree of technique variability, especially concerning the target cells utilized to determine such titers. Accordingly, we decided to use A2 and donor RBCs as well as our standard A1 RBCs in our assays, in order to determine the differences in titer when various A subtype cells are utilized as the target. Our case is a 54 year old male; 0% CPRA, blood group O recipient, whose donor was ABO typed as a non-A1. Flow T and B cell crossmatch negative. The transplant program decided to move forward with the ABO incompatible transplant since no other live donors were available. Determination of the Anti-A titer was as follows: Recipient sera was serially diluted with saline from 1:1 to 1:512. One drop of RBC suspension is added to 2 drops (100 ul) of each sera dilution. Three different titrations were performed using commercially produced A1 and A2 RBC as well as donor RBC. Tubes were incubated at RT for 30 minutes, centrifuged and agglutination macroscopically observed and recorded. Tubes were then incubated at 37C for 30 minutes, washed 4 times with saline, IgG added then centrifuged and agglutination recorded again. This procedure allows for determination of both IgM and IgG antibodies against blood group A antigens. IgG titers were 1:16 with A1 RBC; 1:8 with A2 RBC; and 1:8 with donor RBC. Our transplant program considers an IgG titer less than or equal to 1:8 acceptable and the transplant was performed. Recipient is out 11 weeks with no rejection episodes.