DRB1 allele frequencies in rheumatoid arthritis patients and their correlation with anti-cyclic citrullinated peptide antibodies severity marker


Genetic influence, mainly the HLA-DRB1 on the predisposition of rheumatoid arthritis (RA) disease course is highly contradictive. This study aimed to shed spot light on the DRB1 genetic constitutions and their influence on the anti-citrullinated peptide autoantibodies (ACCP) modulation as a disease activity marker in Iraqi RA patients. A total of 110 RA patients and 50 healthy controls were enrolled in the study. Their HLA-DRB1 allelic constitution and ACCP serum level were evaluated highly sensitive ELIZA technique. The results reveals that the highest DRB1 allele frequencies were in *03, followed by *13, *11, *04, and *07. The majority of Iraqi patients were with positive ACCP and the frequency of this positivity were highest in *10, *16, followed by *04, *03, *11, *08, and *07, allele groups. This study also found that the highest ACCP mean titers were in the allele *13 followed by *11, *04 and *07. In addition, DRB1 *13, 13 homozygotic allelic combination was the highest in frequency (9.1%) and mean titer (3271.7 U/ml) among positive ACCP combinations, followed by *11, 7, *11, 4 and 11, 15. Finally, 44% of the RA-patients DRB1 allelic combination were RA-restricted, whereas 57.1% of the healthy control DRB1 allelic combinations were control-restricted. In conclusion, the distribution of the DRB1 alleles among Iraqi RA patients as well as their ACCP positivity was not subjected to the SE allele roles, and in addition, the presence of RA-restricted and control-restricted allelic combinations is a novel result and of value in differentiating the at-risk from the protecting allelic combination.