title: Calculations show substantial serial engagement of T cell receptors.
abstract: The serial engagement model provides an attractive and plausible explanation for how a typical antigen presenting cell, exhibiting a low density of peptides recognized by a T cell, can initiate T cell responses. If a single peptide displayed by a major histocompatibility complex (MHC) can bind, sequentially, to different T cell receptors (TCR), then a few peptides can activate many receptors. To date, arguments supporting and questioning the prevalence of serial engagement have centered on the down-regulation of TCR after contact of T cells with antigen presenting cells. Recently, the existence of serial engagement has been challenged by the demonstration that engagement of TCR can down-regulate nonengaged bystander TCR. Here we show that for binding and dissociation rates that characterize interactions between T cell receptors and peptide-MHC, substantial serial engagement occurs. The result is independent of mechanisms and measurements of receptor down-regulation. The conclusion that single peptide-MHC engage many TCR, before diffusing out of the contact region between the antigen-presenting cell and the T cell, is based on a general first passage time calculation for a particle alternating between states in which different diffusion coefficients govern its transport.
authors.affiliation: Department of Mathematics and Statistics, University of New Mexico, Albuquerque, New Mexico 87131, USA.
authors.forename: C
authors.initials: C
authors.lastname: Wofsy
authors.forename: D
authors.initials: D
authors.lastname: Coombs
authors.forename: B
authors.initials: B
authors.lastname: Goldstein
mesh_terms: D000938:Antigen-Presenting Cells / Q000276:immunology; D055592:Biophysical Phenomena; D001703:Biophysics; D004058:Diffusion; D008285:Major Histocompatibility Complex; D008954:Models, Biological; D010455:Peptides / Q000276:immunology / Q000378:metabolism; D011485:Protein Binding; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry* / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D010455:Peptides; D011948:Receptors, Antigen, T-Cell