Significant associations of HLA-B*5101 and B*5108, and lack of associationof class II alleles with Behcet's disease in Italian patients

Behcet's disease has been known to be strongly associated with human leukoc yte antigen (HLA) B51, one of the split antigens of HLA-B5, An increased in cidence of HLA-B51 in the patient group has also been reported in an Italia n population. Since the B51 antigen has been recently identified to compris e nine alleles, B*5101-B*5109, we performed HLA-B51 allele genotyping by th e polymerase chain reaction-sequencing based typing . (PCR-SBT) method as w ell as serological HLA-A and -B typing among 21 Italian patients with Behce ts disease in order to investigate whether there is any correlation of one particular B51-associated allele with Behcet's disease. In addition, HLA cl ass II genotyping was performed by the PCR-restriction fragment length poly morphism (RFLP) method. As a result, only the phenotype frequency of the B5 1 antigen was found to be significantly increased in the patient group as c ompared to the ethnically matched control group by the corrected P-value an alysis (71.4% in patients vs. 17.9% in controls; chi(2) = 14.26, Pc=0.0042, R.R.=11.5), In the B51 allele genotyping, 11 out of 15 B51-positive patien ts were B*5101 and the remaining four were B*5108, whereas all of 5 normal controls were B*5101, showing significant association of each allele with B ehcet's disease. No significant difference was observed between the patient and control groups in the HLA class II allelic distribution. This study re vealed a strong association of Behcet's disease in Italian with B*5108 as w ell as B*5101, providing important insight into the molecular mechanism und erlying an FILA association with Behcet's disease.