MHC class II antigens on lung epithelial of human fetuses and neonates. Ontogeny and expression in lungs with histologic evidence of infection.

An immunohistochemical study with anti-HLA-DP, anti-HLA-DQ and anti-HLA-DR monoclonal antibodies was carried out on lung tissue from 29 fetuses and 19 infants that died within the 1st year of life. The aim of the study was to verify the influence of lung maturation and lung inflammation, caused by intrauterine infection, on the expression of MHC class II antigens on lung epithelia. No positive reaction of lung epithelia was noticed in 6 fetuses of less than 21 weeks' gestation. In fetuses of more than 21 weeks' gestation, lung inflammation strongly correlated with the expression of MHC class II subregion products on lung epithelia. All 4 fetuses with histopathologic evidence of lung infection but only 4 out of 23 fetuses without lung inflammation bore HLA-DR antigens on their immature cuboidal alveolar epithelium. Within the bronchial epithelial layers only scattered MHC class II positive epithelia were found. After birth, MHC class II antigens were almost constantly detected on cuboidal type II pneumocytes of inflamed and noninflamed lung tissue as well. Only 3 infants that died within the 1st week of life did not show any MHC class II antigen expression on their lung epithelia.