Background: Methotrexate (MTX) represents the most used anti-rheumatic drug in rheumatoid arthritis (RA). HLA-G antigens are inducible non classical MHC class Ib molecules important in maintaining anti-inflammatory conditions. HLA-G gene is characterized by a deletion/insertion polymorphism of 14 bp, that controls the specific mRNA stability and the protein levels. It has been reported that MTX therapy mediates an increase of Interleukin-10 (IL-10) producing cells. This cytokine up-regulates HLA-G expression.
Objectives: To test the hypothesis of a MTX mediated HLA-G production and the possible relationship between the HLA-G 14 bp polymorphism and therapeutic responsiveness to MTX.
Methods: Peripheral blood mononuclear cells (PBMCs) from 25 healthy subjects and 5 no-MTX-treated RA patients were activated with different MTX concentrations. sHLA-G and IL-10 production was investigated by specific immunoenzimatic assay (ELISA). HLA-G 14 bp polymorphism genotyping was also performed in 162 healthy subjects and in 156 RA patients, defined as "responders" (n=88) and "non responders" (n=68) to the MTX therapy after a 6 months therapeutic trial, on the basis of EULAR response criteria.
Results: MTX activation induces the production of sHLA-G molecules. A significant association was observed between the highest sHLA-G concentrations and the -14/-14 bp genotype. The analysis of the HLA-G 14bp polymorphism in MTX treated RA patients confirmed an increase of the -14/-14 bp genotype in the responder group (p = 0.036; Fisher exact p test) (OR = 2.77 [95%CI 1.19 - 6.45] logistic regression model).
Conclusion: Our results suggest that MTX induces the production of anti-inflammatory sHLA-G molecules that concur to the overall therapeutic response. Furthermore, the association between -14/-14 bp genotype and MTX responsiveness, indicates that HLA-G 14 bp polymorphism may be useful in the therapeutic decision during the early phases of the disease. A prospective study aimed to confirm these data is ongoing.
References: Carosella ED, Moreau P, Aractingi S, Rouas-Freiss N. HLA-G: a shield against inflammatory aggression. Trends Immunol 2001; 10: 553-555.
Hviid TV, Rizzo R, Christiansen OB, Melchiorri L, Lindhard A, Baricordi OR. HLA-G and IL-10 in serum in relation to HLA-G genotype and polymorphisms
