To analyze the association between human leukocyte antigen (HLA) and insulin-dependent diabetes mellitus (IDDM) in the Egyptian population for the first time and, thus, to determine the frequency of risk-associated alleles identified by a genomic HLA class II typing. Egyptians are genetically classified as North Africans and considered to be between Caucasoids and Africans (closer to Caucasoids).
HLA class II typing was performed for 50 IDDM patients and 50 healthy control subjects by a restriction fragment-length polymorphism (RFLP) technique. The analysis of position 57 of the DQB1 molecules was conducted by polymerase chain reaction and specific sequence oligonucleotide hybridization.
The frequency of DRB1*0301-DRB3*0201-DQA1*0501-DQB1*0201 haplotype was 43.9% in the IDDM patients and 7.1% in the control subjects (P < 0.00001), reflecting the increased prevalence of DQA1*0501 susceptibility allele coding for arginine (Arg) in position 52 and DQB1*0201 susceptibility allele non-coding aspartic acid (Asp) at position 57. Alleles DQB1*0601 and 0603, both carrying Asp at position 57 of the β-chain, and DQA1*0103, encoding a non-Arg 52 alpha-chain, were significantly decreased among the IDDM patients. The presence of four susceptibility residues (two DQA1 Arg 52+ and two DQB1 Asp 57−) conferred the highest relative risk at 20.2. On the other hand, homozygous genotypes for DQA1 non-Arg 52 and DQB1 Asp 57 were found only in the control group.
IDDM susceptibility and resistance in the Egyptian population is strongly associated with the expressed DQ α- and β-heterodimers in a dose-effective manner, as already defined in many different ethnic groups.
