Human-platelet-antigen and neutrophil-antigen gene frequency in the Italian population determined by polymerase chain reaction with sequence specific primers.

Sir, Platelets and neutrophil antigen systems play important roles in immune-mediated disorders, since the respective alloantibodies and autoantibodies mediate immune thrombocytopenia and granulocytopenia. Serologic typing for human platelet antigen (HPA) and neutrophil-antigen (NA) systems is well developed but good quality sera are available only in a few specialized laboratories while DNA based methods now afford a way round the limitations of the serologic technique.1 In the Italian Caucasian population only the distribution of HPA-1 dialleles has been described2-5 and there are few data describing the distribution of NA systems among the Caucasian population.6,7 We studied the genotype and gene frequency of HPA-1,2,3,5 and NA1 and NA2 systems by polymerase chain reaction sequence specific primers (PCR-SSP) in 200 randomly selected healthy volunteer blood and bone marrow donors, belonging to the Italian Caucasian population. We evaluated the frequency of HPA and NA system genotypes and from these data obtained the gene frequencies with standard error (Table 1). All the alleles of the HPA-1,2,3,5 systems are present in the Italian Caucasian population with the gene frequency of alleles HPA-1a, 2a, 3a, 5a being 0.86±0.017, 0.87±0.016, 0.72±0.022, 0.785±0.02, which is greater than the gene frequencies of HPA-1b, 2b, 3b, 5b (0.14±0.017, 0.13±0.016, 0.28±0.022 and 0.225± 0.02 respectively). The homozygous genotypes have a frequency of 78, 76, 53, 58.5% for HPA-1a/a, 2a/a, 3a/a, 5a/a. This is more frequent than heterozygous patterns HPA-1a/b, 2a/b, 3a/b, 5a/b (16, 22, 38 and 40%) and homozygous HPA-1b/b, 2b/b, 3b/b, 5b/b (6, 2, 9, 1.5%) respectively. The genotype patterns evaluated in the Italian population overlap those observed in other Caucasian populations but a few differences emerge: in the Asian population HPA-1a/a, HPA-2a/a, HPA-5a/a are the most commonly present patterns, occurring with a percentage of 99, 95 and 93, respectively, whereas in the Italian population the frequencies are 78, 76, 58.5 respectively.2,8 The NA system is represented by the two alleles NA1 and NA2. Here the gene frequency of NA2 (0.692±0.023) is more frequent than that of NA1 (0.282±0.022). In particular the homozygous NA1 genotype (10.5%) occurs at a lower rate than the heterozygous NA1/NA2 (35.5%) or homozygous NA 2 pattern (54%), the last being the most represented genotype in several Caucasian populations. We found that gene NA2 is more frequent in the Italian population (0.692) which is in accordance with the reported NA phenotype in other white populations (European and North American),6,7 in contrast with the gene frequency of 0.65 and 0.68 for NA1 and 0.30 and 0.31 for NA2 reported for the Japanese and Chinese populations, respectively.9 PCR-SSP applied to the typing of HPA and NA systems is thus an available tool, and a way to replace serologic typing, especially in patients who are severely thrombocytopenic and neutropenic, and in prenatal diagnosis. The simplicity and accuracy of this method for platelet and granulocyte investigation in patients and donor recommend its widespread application.