Although the requirement for these macrophages to maintain the inflammatory milieu in Crohn’s disease, ulcerative colitis, idiopathic pulmonary fibrosis, nonspecific interstitial pneumonia, chronic obstructive pulmonary disease, rheumatoid arthritis, systemic lupus erythematosus, sarcoidosis, psoriasis, and scleroderma has not been established, successful therapy of several of these diseases, regardless of the drug used, has been shown to cause disappearance of FR-β-positive macrophages from the inflamed lesions [40, 41]. This evidence concerns the gene FOLR2 and rheumatoid arthritis.