IMMUNOGENETICS OF HENOCH-SCHOENLEIN-DISEASE

In order to investigate the genetic basis of susceptibility to Henoch- Schoenlein purpura (HS), blood samples of 152 patients, 105 of whom ha d renal disease, were collected in a two-step study. The evaluation of DRB, DQB and DQA polymorphism was done by analysis of the restriction polymorphisms produced by TaqI enzyme. DRB107 was less frequent in p atients than in the control group (gene frequency 0.09 and 0.18, respe ctively; P = 0.0023), whereas 64% of the patients were positive for DR B101 and/or DRB1*11 compared with 48% of the control group (P = 0.006 9). Polymerase chain reaction-sequence-specific oligonucleotide (PCR-S SO) typing of DRB101- and DRB1*11-positive individuals did not show a ny deviation of frequencies of DRB101 subtypes between patients and c ontrols, whereas among DRB111 subtypes DRB1*1104 was significantly in creased in the patients (P-c = 0.033). The comparison between patients with renal disease and those without renal disease showed no signific ant differences in the frequency of the single DRB, DQB and DQA allele s. The study of restriction polymorphisms in the switch region of the constant genes alpha 1, alpha 2 and mu of the heavy chains of immunogl obulins, using the enzyme Sad and a specific probe, did not show any d ifference between 44 patients and 54 controls. This study demonstrates that susceptibility to HS also has a genetic origin: on one hand, the presence of DRB101 or DRB1*11 makes disease onset easier; on the oth er hand, DRB107 could induce some resistance to the disease. It is su ggested that, as well as for other diseases caused by an impaired immu ne response, single amino acids in a key position in the HLA-DRB molec ule make it more or less easy to recognize some antigenic peptide, tow ards which an immune response leading to disease is triggered.