Immune Cytolysis of Three Mouse Ascites Tumors

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Abstract
Summary: Immune cytolysis of L4946 leukemia, Sa IA and EA Ca cells has been investigated further in an assay that uses microscopic observation to determine its end point of 50% cell deformation. The effects of adding low concentrations of Ca++ and Mg++ ions to the assay system were relatively slight. The relationship between cytolytic titer and cell concentration at constant complement concentration approached linearity at the lower cell concentrations assayed. Complement was titered against all three cell types and slopes of the von Krogh plots of the titers were evaluated. Criteria are given for choosing optimal assay conditions for titration of complement. The effect of complement concentration on the assay of cytolytic antibody was investigated, and criteria are given for choosing optimal assay conditions. Supernatants separated following cytolytic titer experiments were analyzed. For Sa IA and EA Ca cells, appreciable free cytolysin appeared only at antiserum levels causing close to complete lysis of the cells; for L4946, free antibody appeared at lower initial levels of antiserum. For all three cell types, complement fixation increased sharply with increase in percentage of deformed cells, and was close to maximal at the lowest concentrations of antiserum causing complete lysis.