Immunohistochemical expression of secretory proteins in pneumonic rat lungs

Abstract

The present study evaluated the expression of secretory proteins involving surfactant proteins (SP-A, SP-B, proSP-C), Claracell secretory protein (CCSP), and thyroid transcription factor-I (TTF-I), together with lambda light chain IgG (λ-IgG), proliferatingcell nuclear antigen (PCNA), and lymphocytic phenotypes (T and B cells) in the pneumonic rat lungs. The most prominent grosslesion was severe pulmonary abscession. The lungs showed severe parenchymal destruction and necrosis encapsulated by fibrous tissue.Immunostaining for SPs displayed evident hyperplasia of type II pneumocytes. Immunoreaction to SP-A and SP-B occurred stronglyon the luminal surface of type II cells, and to proSP-C in the perinuclear area. CCSP immunolabeling was seen in the cytoplasm of thelining epithelium of the distal airways. The nuclei of type II cells labeled positively for TTF-I. The λ-IgG positive reaction was found inthe cytoplasm of plasmacytes and B cells. PCNA staining confirmed proliferation of type II cells and fibroblasts. Moderate numbers ofCD3+ T cells, but few CD79αcy+ B cells, were found in the lungs. Statistical analysis found high significance (P < 0.001, except for λ-IgG)between groups. The results of the study revealed that type II cells proliferate highly to restore the damaged lungs and that CCSP andSPs may be used to identify tumors originating from Clara cells and type II pneumocytes of rats, respectively.