HLA class II genes polymorphism in DR4 giant cell arteritis patients

Area of Science:

• Immunogenetics
• Rheumatology
• Molecular Biology

Background:

• Giant cell arteritis (GCA) is an autoimmune vasculitis.
• Previous studies indicated a significant association between HLA-DR4 antigen and GCA.
• Inherited susceptibility to autoimmune diseases is often linked to specific Human Leukocyte Antigen (HLA) alleles, including DR4-associated DQ beta alleles.

Purpose of the Study:

• To investigate the specific DQ beta alleles associated with HLA-DR4 in patients with GCA.
• To determine if specific DQ beta allele clusters within the DQW3 group are more prevalent in GCA patients compared to healthy individuals.

Main Methods:

• DNA samples from 27 HLA-DR4 positive GCA patients were analyzed.
• Restriction fragment length polymorphism (RFLP) analysis using Taq I and Bam HI restriction enzymes.
• Agarose gel electrophoresis and Southern blot hybridization with DR beta, DQ alpha, and DQ beta probes.

Main Results:

• No detectable variants were found within the DR beta hybridization for DR4.
• DQ beta probe analysis identified two clusters among DR4-associated DQW3 alleles: DQW 3.1 (defined by Bam HI 360 Kb fragment) and DQW 3.2 (defined by Taq I 1.9 Kb and Bam HI 11 Kb fragments).
• In the 27 DR4-positive GCA patients, 34% carried DQW 3.1 and 66% carried DQW 3.2. These frequencies did not differ significantly from those observed in healthy controls.

Conclusions:

• While HLA-DR4 is associated with GCA, specific DQ beta allele subtypes (DQW 3.1 and DQW 3.2) do not appear to confer additional susceptibility or resistance in this patient cohort.
• The immunogenetic contribution of HLA-DR4 in GCA may not be solely determined by the specific DQ beta alleles investigated here.