Lectin-induced blast transformation of human lymphocytes.

Abstract

Phytohaemagglutinins1 comprise a class of leguminous plant proteins exhibiting differing specificities for the binding of carbohydrate residues. Despite their shared ability to induce specific precipitation of various polysaccharides, glycoproteins, blood group substances and cellular membranes, only a few phytohaemagglutinins are known to be capable of inducing blast transformation of small lymphocytes. Among such phytomitogens are the lectins from Phaseolus vulgaris2, Lens culinaris3, Wistaria floribunda4 and Canavalia ensiformis5,6. The use of concanavalin A (con A) from Canavalia ensiformis in the detection and preliminary characterization of carbohydrate-containing polymers has been established7. Con A also has been shown to be capable of distinguishing between transformed and normal cells; in vitro agglutination of transformed cells occurs under conditions which produce little agglutination of most normal cells8. A similar preference of con A for tumour cells is exhibited in vivo, resulting in diminished survival of mouse tumour cells (to 1% at 100 mg kg−1 i.p.) (H. Lin, W. R. Bruce and M. J. Walcroft, submitted for publication). The efficacy of con A as a therapeutic agent, however, has been limited by its toxicity and therefore it is of interest to study: (1) other lectins which might manifest similar biological activities but with diminished toxicity; (2) means of chemical modification which might lower con A toxicity without concomitant loss of activity.