RECEPTOR MOBILITY AND ITS COOPERATIVE RESTRICTION BY LIGANDS

The emphasis is on the phenomenon of restriction of receptor mobility in lymphoid cells by ligands such as Concanavalin A [Con A], a phenomenon discovered in recent years using morphological techniques. A method for studying this phenomenon is discussed. This consists of quantitatively measuring the active sites on cell-bound lectin molecules by subsequent fixation of horse-radish peroxidase. This study has shown a cooperative binding of Con A to cells which corresponds to a modification of the membrane, leading to the recruitment of new receptors. The existence of a post-binding event, that has been called micro-redistribution, was shown at 4.degree. C, through the use of peroxidase binding to cell-bound lectin. A cooperative restriction of receptor microredistribution is observed when the cooperative recruitment of receptors induced by increasing concentrations of Con A occurs. Both phenomena are modulated by drugs such as colchicine and cytochalasin B. Density and distribution of receptors may be dependent upon the state of a multimeric submembrane structure which is still functional at 4.degree. C.