Herpes simplex-specific IgG subclass response in herpetic keratitis.

The measurement of the local IgG response in ocular Herpes simplex virus infection presents particular problems due to the difficulty in obtaining sufficient tear samples and the possible transudation of IgG from the serum to the inflamed eye. Using specific monoclonal antibodies to Human IgG subclasses in an enzyme-linked immunoabsorbant assay (ELISA) the local IgG antibody response in Herpes simplex keratitis was analysed. All serum samples from patients and controls contained quantifiable levels of HSV specific IgG1 and IgG4 antibody. Comparison of serum antibody levels with tear levels for patients showed that HSV specific IgG1 serum concentrations were 16.1 fold or more higher than in tears, whereas IgG4 concentrations were only 6.5 fold higher in serum than in tears. This difference was not apparent in the control group. Radioimmunoprecipitation assay of 35S-methionine labelled HSV antigens revealed only minor differences in the protein profiles produced by immunoprecipitation using serum or tear antibody. These results suggest a role for IgG4 antibodies in mucosal immunity in the eye as has been suggested for the mucosal surface of the lung.