HLA class I/class II interaction in early onset pauciarticular juvenile chronic arthritis

The most homogeneous form of juvenile chronic arthritis (JCA), early onset pauciarticular juvenile chronic arthritis (EOPA-JCA), is simultaneously associated with a series of major histocompatibility complex (MHC) class I (HLA-A2) and MHC class II (DR5/8/6-DR/DQ) haplotypes and (DPB1*0201) alleles, resulting in a complex pattern of associations. It is generally accepted that there is no linkage disequilibrium for all combinations of HLA-A2, DR5/8/6-DR/DQ haplotypes, and DPB1*0201. Thus, these associations are considered to be independent of each other. There is strong evidence for HLA-DP/DR-DQ interaction in EOPA-JCA patients. Interaction between different disease-associated HLA alleles could be a general phenomenon and could possibly provide insight into a molecular mechanism of the multiple associations. We investigated by DNA typing a large homogeneous group of EOPA-JCA patients for a possible interaction between HLA-A2 and HLA class II markers.