The activation of cloned macrophages by concanavalin A for tumoricidal effect: Assessmetn of tumor cell cytotoxicity by a clonogenic assay

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Abstract
The activation of pure populations of cloned peritoneal macrophages for tumor cell cytotoxicity by Con A was demonstrated using a recently developed tumor cell clonogenic assay. Cloned macrophages were rendered cytotoxic by Con A at concentrations above 20 μg/ml. The tumor cell cytotoxicity was caused mainly by the tumoricidal activity of the Con A‐activated cloned macrophages. Increasing the Con A‐activation time from 24 hours to 48 hours and 72 hours heightened the cytotoxic activity of cloned macrophages. Cloned macrophages incubated with con A for only 2 hours possessed no cytotoxic effect. Culture fluid from cultures of activated macrophages exerted no tumor cell cytotoxicity. Alpha‐methyl‐D‐mannoside, a specific receptor‐binding inhibitor for Con A, was capable of blocking the activation of macrophages for cytotoxicity at 0.01 M concentration.