To determine whether polymorphisms of the TAP genes, which lie within the major histocompatibility complex (MHC), are associated with juvenile chronic arthritis (JCA).
Eighty five JCA patients and 166 white controls were typed for the TAP gene alleles using ARMS-PCR. The same populations were analysed for DRB1 and DPB1 alleles using PCR-SSO typing.
TAP2B was increased in early onset pauciarticular JCA (EOPA-JCA) compared with controls (62% v 44% Odds ratio (OR) 2.1, 95% CI 0.9-4.7). After allowing for the known linkage disequilibrium between TAP2B and DR1 the association of TAP2B and EOPA-JCA was maintained (OR 3.5, 95% CI 1.3-9.7). HLA-DRB1*04 and TAP2D were found to be in linkage disequilibrium in both the control (delta 0.018 p < 0.05) and JCA patient groups (delta 0.021 p < 0.05). No linkage disequilibrium was found between the TAP and DPB1 alleles.
The association between TAP2B and EOPA-JCA is a further indication of the heterogeneity which exists in this clinically defined subgroup of patients.