The interaction of mammalian cells with antibodies. I.

The single cell plating technique has been applied to quantitation of the reproductive killing of mammalian cells by specific antibodies. This method confirms previous demonstrations by other workers of localization of all the killing activity in the gamma-globulin fraction of specific cell antisera but not of normal sera; the need for complement for the killing action in low doses of antibody and the leakage of cell constituents attending cell killing under these conditions. In concentrations of 4 per cent or higher of heated antiserum cell killing occurs without added complement. The cell plating technique permits highly reproducible quantitation of antibody action and demonstrates antibody activity in sera diluted 1:3000. It permits demonstration of very high degrees of species specificity as shown by virtually complete absence of cross-reaction between antisera to Chinese hamster and S3 HeLa cells, respectively. Somatic cells which have been sensitized by absorption of specific antibody lose their sensitization when incubated at 37 degrees unless complement is added within 1 hour.