Appearance of complement components and immunoglobulins on nasopharyngeal epithelial cells following naturally acquired infection with respiratory syncytial virus.

Nasopharyngeal epithelial cells (NPEC) were collected from 144 infants and children with respiratory syncytial virus (RSV) infection, and were analyzed by fluorescent antibody techniques for the presence of cell-bound complement (C'3), IgA, IgG, and IgM class of immunoglobulins (Ig), and respiratory syncytial virus antigen. Viral antigen was present on the surface of NPEC in 100% of samples obtained in the first 3 days or illness. The percentage of patients positive for RSV antigen declined steadily, so that no patient still expressed viral antigen on NPEC by 57 days after the onset of illness. Cell-bound IgA, IgG, and IgM could be detected in most of the samples tested in the first 13 days after the onset of illness. Subsequently, the frequency of detection of cell-bound Ig gradually declined. Only 8-33% of patients tested 57 days after the onset of illness expressed IgA, IgG, or IgM on NPEC. About 45% of samples tested in the first 8 weeks after the onset of illness exhibited complement binding to NPEC. The percentage of subjects showing cell-bound C'3 reached a maximum at 8-13 says after the onset of illness, while cell-bound C'3 could not be detected in any of the samples collected 57-90 days after the onset of illness. Although cell-bound C'3 was generally present in association with cell-bound Ig on NPEC, in a small percentage (4.6%) of patients cell-bound C'3 could be detected in the absence of any cell-bound Ig. Cell-bound C'3 and IgA, IgG, and IgM were present with equal frequency in patients with all forms of clinical disease caused by RSV, and in patients less than or greater than 6 months of age at the onset of illness.