Interstitial lung disease (ILD) is a lung condition resulting in inflammation and stiffening of the lung, often associated with connective tissue diseases (CTDs). ILD causes reduction in lung volume, shortness of breath, cough and fatigue therefore has high impact on quality of life and is also the leading cause of death in participants with these conditions. The study will assess whether treatment of CTD-ILD participants with belimumab in addition to standard therapy will result in the stabilization and/or improvement of lung function and improve symptoms associated with ILD with an acceptable safety profile.