Abstract
Patients with Systemic sclerosis (SSc) presents immune dysregulation, vasculopathy, and fibrosis of the skin and various internal organs. Pulmonary fibrosis leads to SSc-associated interstitial lung disease (ILD), which is the main cause of morbidity and mortality in SSc. Recently autoimmunity to type V collagen (Col V) has been characterized in idiopathic pulmonary fibrosis and show promise to be related to the development in SSc. Our aim was to evaluate autoimmunity to Col V α1(V) and α2(V) chains and to the antigenic peptides of these Col V chains in early-SSc sera employing lung tissue of SSc-ILD, as antigen source. We found that sera samples from patients with early-SSc were reactive to Col V (41.18%) and presented immunoreactivity for Col5A1(1.049) and Col5A1(1.439) peptides. The IgG isolated from early-SSc patients-anti-Col V positive sera (anti-ColV IgG) was adsorbed with α1(V) chain (anti-ColV IgG/ads-α1(V)) and α2(V) chain (anti-ColV IgG/ads-α2(V)) and biotinylated to evaluate the spectrum of reactivity in SSc-ILD patients lung biopsies by immunofluorescence. The SSc-ILD lung tissue samples immunostained with anti-ColV IgG showed increased green fluorescence in the vascular basement membrane, bronchiolar smooth muscle, and adventitial layer, contrasting with the tenue immunostaining in control lungs. Col V protein expression in these pulmonary compartments immunostained with early-SSc anti-ColV IgG was confirmed by immune colocalization assays with commercial anti-human Col V antibodies. In addition, SSc-ILD lung tissues immunostained with anti-ColV IgG/ads-α1(V) (sample in which Col V α1 chain-specific antibodies were removed) showed decreased green fluorescence compared to anti-ColV IgG and anti-ColV IgG/ads-α2(V). Our data show that autoimmunity to Col V in early-SSc was related to peptides of the α1(V) chain, suggesting that these antibodies could be biomarkers of SSc stages and potential target of immunotherapy with Col V immunogenic peptides.