Lung expression, processing, and localization of inducible SP-C expression. Part A: Top row; Western blot analysis of proSP-C and processed SP-C expression in 55.3/Sftpc -/- mice. An antibody to proSP-C detected proSP-C in the lung homogenates from line 55.3/Sftpc -/- mice maintained on dox (white arrows). Lower row; Antibody to the proteolytically processed SP-C detected the mature 4.5kD SP-C in BAL fluid indicating secretion into the airspace (dark arrows). SP-C protein was only detected in the dox-treated 55.3/Sftpc -/- animals. Lung tissue and BAL fluid from Sftpc +/+ mice are shown as positive controls and Sftpc -/- mice as negative controls for the specificity of SP-C immunostaining. Part B: Immuno-localization of dox-induced proSP-C in the lungs of line 55.3/Sftpc -/- mice: Panel A, Sftpc +/+ lung with no primary antibody. Panel B, Lung tissue from Sftpc +/+ mice ,Immunostaining with anti proSP-C antibody. Staining localized to alveolar type II cells. Panel C, No proSP-C staining was detected in the lungs of line 55.3/Sftpc -/- mice without dox induction. Panel D, proSP-C was detected in a type II cell pattern in lungs of dox treated line 55.3/Sftpc -/- mice, similar to Sftpc +/+ mice in panel B. No alteration of lung morphology was observed by dox treatment.