HLA-DQ gene and cell surface expression in children at type 1 diabetes HLA genetic risk defined by next generation sequencing HLA typing.

Loss of pancreatic islet beta cells precedes the clinical onset of autoimmune (type 1) diabetes. The prodrome can go on for months to years during which time autoantibodies against insulin (IAA), GAD65 (GADA), islet antigen-2 (IA-2A) or ZnT8 (ZnT8A) may be present alone or in various combinations. The disease etiology and pathogenesis are strongly associated with HLA-DQ genotypes but differential expression of HLA-DQ heterodimers on blood cells is poorly investigated. Children at increased HLA genetic risk were followed from birth in the Diabetes Prediction in Skåne (DiPiS) to study factors that would predict clinical onset in children with islet autoantibodies. The aim was to test the hypothesis that the number of islet cell autoantibodies affected the expression of HLA-DQ in sorted white blood cells.

Magnetic microbeads were used to isolate peripheral blood cell subsets in a cross-sectional study of 69 children (age median 13.05; range 10.44-15.05 years of age) with genetic risk of type 1 diabetes defined by Next Generation Sequencing (NGS) of HLA-DRB3,4,5, -DRB1, -DQA1-B1 and DPA1-B1. The children had been followed annually since birth for the appearance of GADA, IAA, IA-2A, or ZnT8A. Flow cytometry was used to investigate HLA-DQ cell surface expression and qPCR for gene expression.

Mean fluorescence intensity (MFI) of HLA-DQ expression was found to vary on different white blood cells and the presence of one islet autoantibody affected MFI. In addition, MFI tended to be lower in cells from subjects with the HLA-DRB1*03:01:01 compared to any other allele variant.

We speculate that HLA-DQ expression may be affected by an on-going islet autoimmunity reflected by a varying number of islet autoantibodies.