BACKGROUND Associations between IgA nephropathy (IgAN) and HLA-DRB1 and -DQB1 alleles have been reported in several ethnic groups. We investigated the association of HLA-DRB1 and -DQB1 alleles with the predisposition for IgAN and disease progression to end-stage kidney disease (ESKD) in Korean patients.

METHODS We analyzed HLA-DRB1 and -DQB1 genotypes in 399 IgAN patients between January 2000 and January 2019 using a LIFECODES sequence-specific oligonucleotide (SSO) typing kit (Immucor, Stamford, CT, USA) or a LABType SSO Typing Test (One Lambda, Canoga Park, CA, USA). Alleles with a significant difference in two-digit resolution were further analyzed using in-house sequence-based typing and sequence-specific primer PCR. As controls, 613 healthy hematopoietic stem cell donors were included. Kidney survival was analyzed in 281 IgAN patients with available clinical and laboratory data using Cox regression analysis. Where needed, P-values were adjusted using Bonferroni correction.

RESULTS The allele frequencies of HLA-DRB1*04:05 (corrected P [Pc]<0.001), -DQB1 *04:01 (Pc=0.048), and -DQB1*03:02 (Pc=0.021) were significantly higher in IgAN patients than in controls, whereas those of HLA-DRB1*07:01, -DRB1*15:01, -DQB1*02:02, and -DQB1*06:02 (Pc<0.001 for all) were significantly lower in IgAN patients than in controls. The allele frequency of HLA-DQB1*05:03 (Pc=0.016) was significantly lower in the ESKD group than in the non-ESKD group; however, there was no significant difference for ESKD progression between these groups.

CONCLUSIONS We report novel associations of HLA-DRB1*15:01, DQB1*02:02, -DQB1*03:02, and -DQB1*04:01 with IgAN. Further studies of HLA alleles associated with IgAN progression in a larger cohort and in various ethnic groups are needed.