CTLA4 and interstitial lung disease: Abatacept (CTLA4-Ig) is a fusion protein consisting of an IgG1 Fc domain fused to the CTLA-4 extracellular domain that has successfully been used to control autoimmune inflammation and interstitial lung disease in patients with CTLA-4 haploinsufficiency and LRBA deficiency (61, 62).