Macrophage migration inhibitory factor (MIF): genetic evidence for participation in early onset and early stage rheumatoid arthritis

Abstract

Macrophage migration inhibitory factor (MIF) is an upstream pro-inflammatory cytokine that is associated with the pathogenesis of autoimmune inflammatory diseases including rheumatoid arthritis (RA). Two polymorphisms in the upstream region exist in the MIF gene and are associated with RA susceptibility or severity in different populations. In this case-control study, we investigated whether MIF polymorphisms are associated with RA susceptibility or activity in a western Mexican population .The relationship of MIF levels with clinical features of disease also was assessed. Genotyping of the -794 CATT5-8 (rs5844572) and the -173 G>C (rs755622) polymorphisms was performed by PCR and PCR-RFLP respectively on 226 RA patients and 210 healthy subjects. Serum MIF levels were determined by ELISA. We found a significant association between the -794 CATT5-8 6,7 MIF genotype with RA. Moreover, we detected an association between the -794 CATT7 allele with early onset RA. The -794 CATT7 and -173(*)C alleles, which are in linkage disequilibrium, were associated with high disease activity on RA patients. A positive correlation between circulating MIF levels and C-reactive protein, erythrocyte sedimentation rate, rheumatoid factor, anti-citrullinated protein/peptides antibodies and TNFα was detected. MIF levels appear to be associated with disease progression rather than disease activity, which is distinct from the established relationship between disease activity and TNFα levels. In conclusion, the MIF gene and protein are associated with RA in a western Mexican population, with a main contribution onto early onset and early stages of disease.

Figure1. MIF levels correlation with clinical features of RA

MIF serum levels positively correlated with C reactive protein (A), erythrocyte sedimentation rate (B), rheumatoid factor (C), anti-citrullinated protein/peptides (D) and TNFα serum levels (E).

Figure 2. Correlation of MIF and TNFα serum levels with disease activity and years of RA evolution

MIF serum levels showed a negative correlation with years of disease evolution (A), indicating a possible role on early RA while no correlation was detected with disease activity (B). On the other hand, TNFα serum levels did not correlate with years of disease evolution (C) but correlated positively with disease activity (D), suggesting participation on active and established RA rather than on early RA.