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Arup K Chakraborty

Publications and source records attributed to Arup K Chakraborty.

5 recordsLinked to original sources
PubMed2003

Low T cell receptor expression and thermal fluctuations contribute to formation of dynamic multifocal synapses in thymocytes.

Mature T cell activation and selection of immature T cells (thymocytes) are both initiated by binding of T cell receptor (TCR) molecules on the surface of T cells to MHC peptide (MHCp) molecules on the surface of antigen-presenting cells. Recent experiments have shown that the spatial pattern of receptors and ligands in the intercellular junction (synapse) is different during thymocyte selection compared with mature T cell activation. Using a statistical mechanical model, we show that lower TCR expression in thymocytes contributes to effecting these differences. An analogy with the phase behavior of simple fluids helps clarify how, for low TCR expression, thermal fluctuations lead to the dynamic synapse patterns observed for thymocytes. We suggest that a different synapse pattern resulting from lower TCR expression, which could mediate differential signaling, may be the reason why TCR expression level is low in thymocytes.

Animals↗
PubMed2002

How and why does the immunological synapse form? Physical chemistry meets cell biology.

During T lymphocyte (T cell) recognition of an antigen, a highly organized and specific pattern of membrane proteins forms in the junction between the T cell and the antigen-presenting cell (APC). This specialized cell-cell junction is called the immunological synapse. It is several micrometers large and forms over many minutes. A plethora of experiments are being performed to study the mechanisms that underlie synapse formation and the way in which information transfer occurs across the synapse. The wealth of experimental data that is beginning to emerge must be understood within a mechanistic framework if it is to prove useful in developing modalities to control the immune response. Quantitative models can complement experiments in the quest for such a mechanistic understanding by suggesting experimentally testable hypotheses. Here, a quantitative synapse assembly model is described. The model uses concepts developed in physical chemistry and cell biology and is able to predict the spatiotemporal evolution of cell shape and receptor protein patterns observed during synapse formation. Attention is directed to how the juxtaposition of model predictions and experimental data has led to intriguing hypotheses regarding the role of null and self peptides during synapse assembly, as well as correlations between T cell effector functions and the robustness of synapse assembly. We remark on some ways in which synergistic experiments and modeling studies can improve current models, and we take steps toward a better understanding of information transfer across the T cell-APC junction.

Antigen Presentation↗
PubMed2002

Correlation of a dynamic model for immunological synapse formation with effector functions: two pathways to synapse formation.

During antigen recognition by T cells different receptors and ligands form a pattern in the intercellular junction called the immunological synapse, which might be involved in T-cell activation. Recently, a synapse assembly model has been proposed, which enables the calculation of the propensity for synapse assembly driven by membrane-constrained protein binding interactions. We bring together model predictions of mature synapse assembly with data on the dependence of T-cell responses on T-cell receptor (TCR)-MHC-peptide (pMHC) binding kinetics. Predictions of mature synapse assembly, based on TCR-pMHC binding kinetics, correlate well with observed cytokine responses by T cells bearing the relevant TCR but not with cytotoxic T lymphocyte-mediated killing. We discuss the suggested different role for the synapse in pre- and post-nuclear activation events in T cells. The view of immunological synapse assembly given here emphasizes the importance of both the on and off rates for the TCR-pMHC interaction and in this context recent data on a positive role for analogs of self-peptides in synapse assembly is considered.

Animals↗
PubMed2002

The synapse assembly model.

A framework for quantitative analysis of the mechanisms underlying immunological synapse assembly has been recently developed. This model uses partial differential equations to describe the binding interactions of receptors and ligands, with the constraint that they are embedded in apposed deformable membranes linked to a cytoskeletal complex.

Animals↗