TRIM21 and interstitial lung disease: Through immunohistochemical staining, studies have observed that TRIM21 is localized in alveolar M2 macrophages in the peripheral lung tissue of SSc-ILD patients and that the accumulation of anti-TRIM21 in bronchoalveolar lavage (BAL) fluid suggests a pathobiological link between TRIM21 and its autoantibodies and the progression of SSc-ILD (126).