Evidence that Thy-1 and Ly-5 (T-200) antigens interact with sulphated carbohydrates.

Recent studies have demonstrated that lymphocytes express an array of cell surface receptors for sulphated polysaccharides (SP). Experiments were undertaken to determine the binding characteristics of these receptors and establish whether any known lymphocyte cell surface antigens interact with sulphated carbohydrates. It was found that murine thymocytes lack receptors for chondroitin-4-sulphate but express saturable, high affinity binding sites for heparin, fucoidan and dextran sulphate, with an apparent affinity constant range of 0.03-2.6 x 10(-9) mol/l. Binding inhibition experiments revealed one class of binding sites on murine thymocytes that is shared by heparin, fucoidan and dextran sulphate and another class of sites that is dextran sulphate-specific. The cell surface receptors for the SP were affinity-purified by applying detergent lysates of 125I-labelled thymocyte membranes to SP-coupled solid supports. It was found that the Thy-1 and Ly-5 (T-200 or leucocyte common antigen) molecules of murine thymocytes bind to sulphated carbohydrates, although the two molecules differed substantially in their reactivity with the four different SP tested. Furthermore, only subpopulations of the Thy-1 and Ly-5 molecules interacted with sulphated sugars. Four additional sulphated carbohydrate-binding molecules were also detected. It is suggested that the SP-binding molecules are involved in the interaction of lymphocytes with glycosaminoglycans on other cells and in the interstitial space.