Changes in thymocyte reactivity to lectins induced by B-cell mitogens of the type of sulphated polyanions

Dextran sulphate, polyvinyl sulphate and carrageenan (but not the other polyanions tested, such as poly I:poly C, poly-L-glutamic acid or E. coli lipopolysaccharide) act synergisticaly with PHA on mouse thymocyte stimulation, as measured by thymidine uptake and blast cell transformation. Furthermore the active compounds shift the dose response of thymocytes to Con A. The effect could be observed in four different strains of mice tested by using normal or cortisone-resistant thymocytes. Two possibilities are envisaged for explanation of these effects: (a) attachment of polyanions by their anionic groups to cell surface constituents and interaction of the sulphate groups of the polymers with plant lectins; and (b) modification of the cell membrane induced by sulphated polymers changing either the binding capacity or the effectiveness of the membrane-associated events leading to thymocyte stimulation by the lectins.