Immunohistochemical studies of complement receptor (CR1) in cases with normal sinus mucosa and chronic sinusitis

The complement receptor (CR1) in the maxillary sinus mucosa of normal patients and in cases of chronic sinusitis was studied with the peroxidase-antiperoxidase, avidin-biotin peroxidase and immunofluorescent methods. CR1 was localized on the ciliary surface and in the cytoplasm of the covering epithelium in both normal controls and the cases of chronic sinusitis. CR1 tended to be denser in the mucosa of chronic sinusitis than in normal mucosa. CR1-binding capacity was also studied with the immunofluorescent method, using C3b-conjugated zymosan. Although CR1 did not bind to C3b in vivo, it was found to bind to C3b in the normal maxillary mucosa when it was treated with C3b-conjugated zymosan. CR1-binding capacity could not be detected in the mucosa from cases with chronic sinusitis, indicating that CR1 was already bound to activated C3b in these cases.