GPI and juvenile idiopathic arthritis: 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).