HA induces FN production by HCs. HCs were cultured for 24 hours at 37°C on glass coverslips that were either untreated or coated with HA. FN was stained by an indirect immunocytochemical method involving anti-FN mAbs and peroxidase-labeled goat antimouse antibody as first and second layers, respectively. This is a representative example of 5 experiments involving 3 different cases of HCL. Original magnification, × 40.