Comparison between HLA class I PCR-ARMS and serologic typing in cadaveric kidney transplantation.

The aim of the present study was to value the possible application of the ARMS method in clinical practice of kidney transplantation and to compare this allelic resolution with serologic techniques. For this purpose, we analyzed the incidence of HLA-A and -B serologic blanks in cadaveric donors, and we used the PCR-ARMS technique to discriminate whether they reflected a homozygous formor a mistyped allelic assignation. PCR-ARMS seems to be a method with an useful applicability in definition of class I compatibility in cadaveric kidney transplant for its speed of execution (4 hours including DNA extraction), ease of result interpretation, and the best resolution in allele definition, even if for the present it is limited by relatively low resolution capability and by the difficulty in distinguishing some alleles and some heterozygote forms, depending on the identical reactivities of some primer mixes for certain allele combinations. It would be advisable to raise the number of mixes available to avoid these problems and to have a higher resolution, expecially for HLA-B antigens. The better definition of HLA-A locus obtained by this molecular method to serologic typing concerned the A19 group, cases in which one allele might mask the presence of the second cross-reactive allele, such as Al 1 missed allele in a donor serologically typed as Al/blank or A24 missed allele in a A2/blank donor or A23,24 in a A9/blank case. Moreover, antigens that one would expect to identify easily by serology, such as Al or A2, can be missed but detected by DNA typing, probably for a low expression of a particular antigen. As regards HLA-B, a more polymorphic locus thanHLA-A, it is very important to obtain a better definition because these antigens are mainly involved, together with HLA class II antigens, in the clinical outcome of the transplant. Therefore, the increase of HLA-B mismatches, found retrospectively in our donor-recipient pairs, underlines the importance of PCR-ARMS and suggests its possible application in routine cadaver donor typing.