Concanavalin A receptors, immunoglobulins, and theta antigen of the lymphocyte surface. Interactions with concanavalin A and with Cytoplasmic structures.

Abstract

The effect of concanavalin A (Con A) on the capping of mouse lymphocyte surface immunoglobulin (surface lg), cross-linked by rabbit anti-mouse Ig antibody, and on the capping of mouse thymocyte 0 antigen, cross-linked by anti-0 alloantibody and rabbit anti-mouse lg antibody, has been studied by immunofluorescence, using fluorescein conjugated Con A and rhodamine-conjugated anti-mouse lg antibody, and by electron microscopy, using native or fluorescein-conjugated Con A and ferritin-conjugated anti-mouse lg antibody.Prior incubation of the cells with Con A inhibited only partially capping of surface Ig, whereas it blocked almost completely capping of 0 antigens. Both on cells with rings and on cells with caps the staining for surface Ig or 0 antigen was superimposed to the staining for Con A. When Con A receptors on spleen cells were capped by Con A at concentrations of 10 ug/ml or higher, and the distribution of surface lg was examined under noncapping conditions, all detectable surface lg were found in the caps. As shown by electron microscopy, surface lg remained dispersed in a layer of Con A. The ability of Con A to cap surface ig was not alterecl by the presence of colchicine or vinblastine. These results suggest that surface lg are cross-linked by Con A to other Con A receptors. In these conditions surface lg behave essentially as Con A receptors, as for example, in their sensitivity to cytochalasin B during inhibition or reversal of capping induced by this drug. The behavior of surface lg parallels that of Con A receptors also in the presence of vinblastine. It is concluded that in the presence of Con A, antimitotic drugs do not modify directly the interaction between Con A receptors and surface lg, but probably influence the capping ability of the Con A receptors or, more in general, affect the ability to elicit movements over the cell surface. The role in capping of cytochalasin-sensitive and vinblastine-sensitive structures is discussed. Both types of structures appear to play an active role in the formation of a cap, although the former probably corresponds to the main mechanical system responsible for the active displacement of cytoplasmic and surface material.

Actin associated with purified lymphocyte plasma membrane

“…In whole lymphocytes, micro filaments are found preferentially underlying the cell surface membrane [4,20] and in surface protrusions such as microvilli [20]. Electron micrographs of the purified plasma membrane vesicles revealed membrane-adherent filamentous material similar in appearance to microfilaments ( fig.…”

“…It has recently been proposed [4,20] that cytoplasmic microfilaments play a key role in the regulation of lymphocyte cell surface receptor mobility. Our results indicate that a protein having a high degree of homology with muscle actin is a major constituent of highly purified preparations of human and pig lymphocyte plasma membrane.…”

“…microfilaments) and monomeric form, has, however, yet to be clearly defined. In the case of lymphocytes, microfilaments have been implicated in various cell surface-mediated phenomena including the capping of surface immunoglobulin [2][3][4][5], lectin-induced mitogenicity [6,7] and lymphocyte-mediated cytotoxicity [8,9]. One possible explanation for the apparent linkage between cell surface events and cytoplasmic microfilaments would be a specific interaction between the filaments and the cell surface (plasma) membrane.…”

Cell surface-associated structural proteins in connective tissue cells.

“…In lymphocytes, the translational movement of cell surface-associated immunoglobulin can be demonstrated directly by the patch and cap formation that occurs after treatment with a divalent antibody (3). It has been suggested that, in both lymphocytes and fibroblasts in suspension, the mobility of some macromolecular components of the membrane is subject to transmembrane control by cellular organelles including microfilaments and microtubules (2,4,5).…”

A kinetic study of membrane immunoglobulin capping by flow cytometry

“…By contrast, the width profiles of cells treated with noninhibitory agents would mimic the width profiles of untreated cells incubated at permissive temperatures. To test this hypothesis the following drugs were used: (1) sodium azide, an inhibitor of capping but not patching (19, ZO), (2) sodium fluoride, which does not interfere with capping (19, ZO), (3) propranolol, a drug that inhibits capping (9, lo), and (4) vinblastine, colchicine, and demecolcine, which reportedly inhibit endocytosis, but not capping (11,19,201. As predicted, cells treated with either azide or propranolol displayed relatively small decreases in their width profiles, and the change in width values was confined to the first 300 sec of the analyses.…”