title: Recovery of soluble sheep erythrocyte receptor from the T lymphocyte surface by proteolytic cleavage.
abstract: Proteolytic digestion of the human T lymphoblastoid cell line (Molt-4) and of peripheral blood lymphocytes by trypsin, chymotrypsin, and pronase results in a progressive, time-and dose-dependent diminution of T lymphocyte-sheep red bloock cell (SRBC) rosette formation, whereas thrombin, plasmin, collagenase, DNAse, and phospholipase have not effect. Complete abrogation of SRBC binding is achieved when lymphocytes (1 x 108/ml) are incubated with either trypsin or chymotrypsin at 10 mug/ml for 30 min, and greater than 50% abrogation is observed between 3 to 10 min. Preincubation of SRBC with the 10 min and 20 min lymphocyte digest supernatants inhibited their subsequent binding by normal T lymphocytes by as much as 64%. Thirty-minute digests were less inhibitory. Equivalent digests from several human B lumphoblastoid cell lines and from a non-rosetting clone of Molt-4 cells were not inhibitory. Polyacrylamide gel electrophoresis followed by elution of serial gel slices revealed four distinct inhibitory bands (I-IV) in the 20-min digest supernatant whereas only bands I-III and band IV were present in the 10-min and 30-min digest supernatants, respectively, suggesting progressive proteolysis of a distinct receptor. These experiments indicate that the binding of SRBC by human T lymphocytes represents a receptor-ligand interaction rather than a nonspecific electrical charge phe nomenon and that the receptor is a discrete molecular species which can be isolated from the surface of T but not B lymphocytes by limited enzymatic proteolysis.
mesh_terms: D001665:Binding Sites; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology; D002918:Chymotrypsin / Q000494:pharmacology; D004912:Erythrocytes / Q000276:immunology*; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000276:immunology; D010447:Peptide Hydrolases / Q000494:pharmacology*; D011402:Pronase / Q000494:pharmacology; D011485:Protein Binding; D013601:T-Lymphocytes / Q000276:immunology*; D014357:Trypsin / Q000494:pharmacology
chemical_list: D008565:Membrane Proteins; D010447:Peptide Hydrolases; D002918:Chymotrypsin; D014357:Trypsin; D011402:Pronase