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Results for “Immunologic Capping”

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PubMed2001

The immunological synapse.

The adaptive immune response is initiated by the interaction of T cell antigen receptors with major histocompatibility complex molecule-peptide complexes in the nanometer scale gap between a T cell and an antigen-presenting cell, referred to as an immunological synapse. In this review we focus on the concept of immunological synapse formation as it relates to membrane structure, T cell polarity, signaling pathways, and the antigen-presenting cell. Membrane domains provide an organizational principle for compartmentalization within the immunological synapse. T cell polarization by chemokines increases T cell sensitivity to antigen. The current model is that signaling and formation of the immunological synapse are tightly interwoven in mature T cells. We also extend this model to natural killer cell activation, where the inhibitory NK synapse provides a striking example in which inhibition of signaling leaves the synapse in its nascent, inverted state. The APC may also play an active role in immunological synapse formation, particularly for activation of naïve T cells.

Animals↗
PubMedDate not supplied

Stability of E-rosettes in aged humans: effect of cytochalasin B and colchicine.

A greater stability of E-rosettes and a reduced rate of capping of sheep erythrocytes are observed in elderly people. The lack of qualitative changes in the sensitivity of these processes to colchicine and cytochalasin B suggests that the function of the microfilaments and the microtubules is not primarily affected by ageing. The density and the affinity of the lymphocytes for sheep erythrocytes do not decrease in aged subjects. So the defective rearrangement of the E-receptors cannot be accounted for by some receptor alteration but points to a possible hindrance of their cross-linking in the membrane or their submembrane connection to the cytoskeleton.

Aging↗
PubMed1988

Isolation of Thy-1 caps and analysis of their phospholipid composition in mouse T-lymphoma cells.

In this study we have used a density perturbation method to isolate anti-Thy-1 antibody-induced Thy-1 caps from mouse T-lymphoma cells in the absence of detergents, and then compared the phospholipid composition of these capped membranes with that of uncapped membranes. Initial phospholipid analysis by two-dimensional thin layer chromatography (2-D TLC) reveals a significant increase in the amount of 32P-labeled phosphatidylcholine in the Thy-1 capped membrane. In contrast, no significant changes are observed in the labeling of phosphatidylserine, phosphatidylethanolamine, or the sphingomyelins. Therefore, it is suggested that phosphatidylcholine may be involved in the organization and/or regulation of Thy-1 antigen redistribution. The composition of phosphoinositide in uncapped and capped membranes was analysed separately using one-dimensional thin layer chromatography (1-D TLC) to resolve phosphatidylinositol (PI), phosphatidylinositol 4-phosphate (PlP), and phosphatidylinositol 4, 5-bisphosphate (PIP2) from all other phospholipids. This analysis reveals a significant reduction in levels of PIP and PIP2, but not PI, in Thy-1 caps. Through the use of ion exchange column chromatography, we have found an increased production of all three species of inositol phosphates during anti-Thy-1 antibody-induced capping. Inositol 1, 4, 5-triphosphate (IP3) shows the most significant increase, compared to the much smaller increases in inositol 4, 5-bisphosphate (IP2) and inositol monophosphate (IP). These results suggest that the binding of anti-Thy-1 antibody to Thy-1 antigen activates phospholipase C which, in turn, initiates polyphosphoinositide turnover and IP3 production. It is proposed that these observed effects are the result of early signal transducing events which are prerequisite steps in Thy-1 receptor cap formation.

Animals↗
PubMed1979

Inhibition of human lymphocyte mitogen and antigen response by a 15,000-dalton protein from feline leukemia virus.

Peripheral blood lymphocyte response of normal human subjects to mitogens and antigens was suppressed by a 15,000-dalton protein (p15) from a C-type feline leukemia virus. Four of six subjects were suppressed 70 to 96% when responding to concanavalin A or phytohemagglutinin in the presence of 5.0 microgram of p15. The three subjects who responded to streptokinase-streptodornase and Candida were suppressed 68 to 91% when cultured with 5.0 microgram of p15. The subviral protein did not appear to be cytotoxic at doses reported. Lymphocyte membrane studies with fluorescein isothiocyanate-concanavalin A revealed a reduction in concanavalin A-induced cap formation of 51 to 91% in the presence of the same dose of p15. These results demonstrate that in vitro immunological dysfunction in human lymphocytes can be induced by a C-type virion protein.

Antigens↗
PubMed1981

Capping of DNA on phytohemagglutinin-stimulated human lymphoblasts.

A portion of the DNA released by PHA-stimulated human lymphoblasts becomes bound to the plasma membranes of the cells and is actively capped. Capping is accompanied by shape change, and caps are localized to uropods. DNA can be exchanged between cells for capping.

Animals↗
PubMedDate not supplied

[Lateral diffusion of the concanavalin A and immunoglobulin receptors on the surface of lymphocyte plasma membranes on exposure to antigen].

The lateral diffusion of integral glycoproteins of lymphocyte plasma membranes is not described only in terms of Brown movement. The development of immune process to the thymus-dependent antigene in vivo induces changes in physico-chemical state of ConA and immunoglobulin receptors of the surface of immuno-competent cells revealed when studying cap formation in vitro.

Animals↗
PubMed1979

Some membrane events occurring during fusion and exocytosis in rat peritoneal mast cells.

We have used the mast cell as a model system for studying some of the membrane events which occur during exocytosis. Our observations indicate that the maximum cluster size of IgE molecules necessary for the 'on' signal to activate a mast cell is ten or less, and that the 'off' signal is not associated with the gross patching or pinocytosis of IgE and its Fc receptors. Furthermore, the use of Con A-Sepharose beads to stimulate mast cells has shown that such signalling is localized to the areas of stimulus, but this localization is not a function of desensitization over the rest of the cell since the subsequent addition of soluble Con A to locally released cells induced generalized degranulation. Ca2+ influx therefore acts in a localized manner to initiate degranulation. Following receptor cross-linking, most of the membrane proteins and the layer of intervening cytoplasm are laterally displaced away from the areas of membrane interaction. This displacement may act as the signal for fusion to occur. The resulting fused bilayers are predominantly lipid, a situation which may be common in all transient membrane fusion.

Animals↗
PubMed1982

Private specificity of H-2Ldx molecule detected serologically by a surface antigen redistribution method (capping).

The presence of H-2.1 positive-H-2.63 negative molecules, H-2Ldx, in the products of the Ddx region was originally detected in H-2dx inbred strains GRS/A and LIS/A (Snoek et al. 1979). This study confirms the existence of H-2Ldx molecules in 2 congeneic strains with a H-2dx haplotype on C3H (C3H.LG strain) and B10 (B10.GR strain) background. Besides anti-H-2.1-like antibodies present in anti-Ddx allo-antiserum, monoclonal antibody d anti-k (H100-5/28, H-2.m3) was shown to react with H-2Ldx molecule. Furthermore, evidence is shown that H-2Ldx molecule has a unique specificity, which is detected serologically in a capping experiment.

Animals↗