Tear immunoglobulins measured by ELISA.

The authors applied an ELISA to measure IgG, IgA, and IgM concentration in tears from 20 normal subjects. This assay was more sensitive than any other previously reported technique to quantitate tear immunoglobulin. Only 2 microliter of tears were required and concentrations as small as 1 ng/ml could be detected. IgM was present in all samples at a geometric mean level of 5.6 micrograms/ml. Mean IgA level was 186 micrograms/ml and mean IgG was 6.7 micrograms/ml. No correlation was found between tear and serum levels, suggesting that local synthesis was responsible for most of the tear immunoglobulin. This ELISA offers a sensitive and reliable method to analyze very small volumes of tears. It can be modified to test for many different antigens and antibodies.