A non-lysozyme antibacterial factor was found in normal, non-stimulated tears. Lysozyme content was measured by spectrophotometric assay. Total antibacterial activity was measured in terms of a zone of inhibited growth on an agar plate inoculated with M. lysodiekticus, and it was discovered that total antibacterial activity was 200 times greater than could be attributed to the amount of lysozyme present. Electrophoresis separated the lysozyme from the non-lysozyme antibacterial factor. The latter had no lysozyme activity by spectrophotometric assay, but exhibited antibacterial activity very close to the total tear activity on agar plates. This factor is destroyed by heating to 100 °C in an acid medium, whereas lysozyme is not. Dialysis and Sephadex gel filtration separated the factor from other constituents of tears and approximated the molecular weight as between 5000 and 7500. The non-lysozyme antibacterial factor exhibits activity against a wide spectrum of conjunctival inhabitants including pathogenic species, whereas lysozyme even in high concentrations, does not.
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