Since MTX also decreased IL-6 synthesis after stimulation with LPS of PBMC from juvenile idiopathic arthritis (JIA) (96) and in the GPI-arthritis model (glucose-6-phosphate isomerase-induced arthritis model), MTX potently inhibits the development of arthritis, and this effect relates to the progressive reduced SLC19A1 expression (the folate carrier SCL19A1) (97). Here, GPI is linked to arthritic joint disease.