We describe a streamlined method for the simultaneous identification of alleles of the human platelet antigens (HPA) 1-5. The method employs the polymerase chain reaction with sequence specific primers (PCR-SSP). Although PCR-SSP has been applied to HPA genotyping, all methods previously described have required different reaction mixes and PCR conditions. We have designed a set of sequence-specific primers for HPA 1-5 which react optimally under identical reaction and PCR conditions. Comparative testing with reference samples gave 100% concordance. The advantages of this method include speed; accuracy; smaller sample requirements and no reliance on human typing sera or platelet integrity. The method also has the potential to be applied to amniotic fluid. Simplified DNA techniques will lead to more extensive and proficient platelet antigen typing. This will facilitate accurate laboratory diagnosis of alloimmune thrombocytopenia and the provision of HPA-matched blood products.
Accurate typing of patients for platelet-specific (human platelet) antigens (HPA) is required in several different clinical situations, and blood services need to maintain panels of HPA-typed apheresis platelet donors and whole-blood donors to support HPA alloimmunized patients. Six clinically relevant HPA alloantigen systems have been described and, in addition, a significant number of HPA alloantigens with a highly skewed allele frequency or of very low immunogenicity have been reported. Certain well-characterized biallelic systems such as Gov have not as yet been included in the HPA nomenclature but are included in this review. Biochemical studies have identified the platelet membrane proteins on which the HPA antigens are localized. Cloning of the genes encoding these proteins and the realization that there is adequate mRNA in fresh platelets has led to identification of the molecular basis of HPA antigens over the last decade. All but one of the biallelic platelet-specific alloantigen systems are based on a single nucleotide polymorphism in the DNA sequence, corresponding to a single amino acid substitution in the encoded primary protein sequence. The discovery of the genetic basis of the alloantigens has allowed the development of polymerase chain reaction-based techniques for HPA genotyping using genomic DNA. The genetic basis of the HPA alloantigens, the most commonly used genome typing techniques and their pitfalls, and future developments, are discussed in this review.
Mismatch for the adhesion molecule CD31 (PECAM-1) has been associated in some studies with graft-versus-host disease (GVHD), suggesting a role for CD31 as a minor histocompatibility antigen. We examined polymorphisms of the CD31 (PECAM-1) gene in 74 patients and their human leukocyte antigen-matched sibling donors, comparing CD31 genotype with outcomes of occurrence of GVHD and survival using regression analysis. Polymorphisms in codon 125, 563, and 670 are strongly linked forming conserved haplotypes. Donor CD31 (val/asn/gly) haplotype was associated with acute GVHD (P=0.004, odds ratio 7.5). In addition, donor heterozygosity at codon 563 was significantly associated with worse overall survival after correcting for other known variables by regression modeling. Peptide binding predictions support the hypothesis that CD31 could act as a minor histocompatibility antigen. Assessment for CD31 gene status may be of value in pretransplant assessment of bone marrow transplant recipients and donors for prediction of likely transplant-related complications.
A total of 231 sibships of the same sex (186 female, 45 male), in which the proband had classical or definite rheumatoid arthritis (RA) have been selected from rheumatology clinics. Each sibship member was questioned about symptomatic joints, which were then examined. Hospital records, radiographs, and rheumatoid factor measurements aliowed each sibling to be classified as having classical, definite, probable, or no RA. Each sibling was typed for HLA-A and B and was classified as sharing two, one, or zero HLA haplotypes with the proband.Concordance rates for classical and definite RA were three times greater in sibships of women than ofmen (9.3 v 300/6). Concordance rates in HLA identical sibships were twice those in hemi-and non-identical sibships (15.5, 7-1, and 5-2%, respectively). Probable RA was more common in male and HLA hemi-and non-identical sibships. These results suggest that female sex and the two inherited HLA haplotypes are important for the presence and expression of RA.Although environmental factors may be shared more in twins than siblings, a concordance rate of 20-5% in seropositive HLA identical sibships of the same sex compared with 300/o in monozygotic twins suggests that sex and HLA type account for about two thirds of the inherited risk of RA.
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