Visualization of signaling pathways and cortical cytoskeleton in cytolytic and noncytolytic natural killer cell immune synapses

Summary:  Recent applications of imaging approaches and other methods of cell biology have provided high‐resolution visualization of the location of fluorescent proteins in living and fixed cells during cell–cell interactions between lymphocytes, antigen presenting cells and target cells. We review the composition and dynamics of molecular and cytoskeletal events occurring during natural killer cell interactions with susceptible and nonsusceptible target cells. The natural killer cell immune synapse and the concomitant changes in cytoskeletal components and cytoplasmic organelles are described. The findings are compared with the observations made in T helper cells and cytotoxic T cells. It is concluded that the cytolytic immune synapses display spatial–temporal dynamics that are accelerated as compared with T helper cells. In addition, the cytolytic conjugates have unique characteristics relating to their effector function. Furthermore, the natural killer cell immune synapses in cytolytic and noncytolytic interactions are distinctly different and display patterns consistent with characteristic signaling pathways identified in biochemical studies of disrupted cells. The precise relationship between different stages of the natural killer cell immune synapse formation and progression in signal transduction pathways is yet to be established.

[1]  A. Diefenbach,et al.  The innate immune response to tumors and its role in the induction of T‐cell immunity , 2002, Immunological reviews.

[2]  J. Madrenas,et al.  Clustering of a lipid-raft associated pool of ERM proteins at the immunological synapse upon T cell receptor or CD28 ligation. , 2002, Immunology letters.

[3]  E. Ingulli,et al.  In Situ Analysis Reveals Physical Interactions Between CD11b+ Dendritic Cells and Antigen-Specific CD4 T Cells After Subcutaneous Injection of Antigen1 , 2002, The Journal of Immunology.

[4]  P. Leibson,et al.  Natural killer cell activation in mice and men: different triggers for similar weapons? , 2002, Nature Immunology.

[5]  Michael J. Byrne,et al.  Wiskott–Aldrich syndrome protein is required for NK cell cytotoxicity and colocalizes with actin to NK cell-activating immunologic synapses , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[6]  D. Davis,et al.  Assembly of the immunological synapse for T cells and NK cells. , 2002, Trends in immunology.

[7]  F. Sánchez‐Madrid,et al.  TCR Engagement Induces Proline-Rich Tyrosine Kinase-2 (Pyk2) Translocation to the T Cell-APC Interface Independently of Pyk2 Activity and in an Immunoreceptor Tyrosine-Based Activation Motif-Mediated Fashion1 , 2002, The Journal of Immunology.

[8]  Balbino Alarcón,et al.  Recruitment of Nck by CD3ϵ Reveals a Ligand-Induced Conformational Change Essential for T Cell Receptor Signaling and Synapse Formation , 2002, Cell.

[9]  Brian A. Smith,et al.  CD28 plays a critical role in the segregation of PKCθ within the immunologic synapse , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[10]  L. Atherly,et al.  The Absence of Itk Inhibits Positive Selection Without Changing Lineage Commitment1 , 2002, The Journal of Immunology.

[11]  R. Germain,et al.  Dynamic Imaging of T Cell-Dendritic Cell Interactions in Lymph Nodes , 2002, Science.

[12]  É. Vivier,et al.  Lymphocyte activation via NKG2D: towards a new paradigm in immune recognition? , 2002, Current opinion in immunology.

[13]  R. Bleackley,et al.  Cytotoxic T lymphocytes: all roads lead to death , 2002, Nature Reviews Immunology.

[14]  G. Koretzky,et al.  Control of T Cell Function by Positive and Negative Regulators , 2002, Science.

[15]  J. D. Dal Porto,et al.  B Cell Antigen Receptor Signaling: Roles in Cell Development and Disease , 2002, Science.

[16]  N. Mitchison,et al.  The immunological synapse. , 2002, Molecular immunology.

[17]  R. Zaru,et al.  Cutting Edge: TCR Engagement and Triggering in the Absence of Large-Scale Molecular Segregation at the T Cell-APC Contact Site1 , 2002, The Journal of Immunology.

[18]  R. Aebersold,et al.  The Direct Recruitment of BLNK to Immunoglobulin α Couples the B-Cell Antigen Receptor to Distal Signaling Pathways , 2002, Molecular and Cellular Biology.

[19]  Kenneth G. Johnson,et al.  Polar Redistribution of the Sialoglycoprotein CD43: Implications for T Cell Function1 , 2002, The Journal of Immunology.

[20]  R. Tan,et al.  Association of the X-linked Lymphoproliferative Disease Gene Product SAP/SH2D1A with 2B4, a Natural Killer Cell-activating Molecule, Is Dependent on Phosphoinositide 3-Kinase* , 2002, The Journal of Biological Chemistry.

[21]  L. Lanier,et al.  Direct Recognition of Cytomegalovirus by Activating and Inhibitory NK Cell Receptors , 2002, Science.

[22]  T. Zal,et al.  Inhibition of T cell receptor-coreceptor interactions by antagonist ligands visualized by live FRET imaging of the T-hybridoma immunological synapse. , 2002, Immunity.

[23]  B. Zhong,et al.  Syk Regulation of Phosphoinositide 3-Kinase-Dependent NK Cell Function1 , 2002, The Journal of Immunology.

[24]  Bo Dupont,et al.  Cutting Edge: Differential Segregation of the Src Homology 2-Containing Protein Tyrosine Phosphatase-1 Within the Early NK Cell Immune Synapse Distinguishes Noncytolytic from Cytolytic Interactions1 , 2002, The Journal of Immunology.

[25]  J. Trapani,et al.  Cytotoxic cell granule-mediated apoptosis: perforin delivers granzyme B-serglycin complexes into target cells without plasma membrane pore formation. , 2002, Immunity.

[26]  Michael Loran Dustin,et al.  T Cell Receptor Signaling Precedes Immunological Synapse Formation , 2002, Science.

[27]  J. Ortaldo,et al.  Natural cytotoxicity uncoupled from the Syk and ZAP-70 intracellular kinases , 2002, Nature Immunology.

[28]  J. Coligan,et al.  Structure and function of major histocompatibility complex (MHC) class I specific receptors expressed on human natural killer (NK) cells. , 2002, Molecular immunology.

[29]  Eric O Long Tumor cell recognition by natural killer cells. , 2002, Seminars in cancer biology.

[30]  M. Robertson Role of chemokines in the biology of natural killer cells , 2002, Journal of leukocyte biology.

[31]  Peter Parham,et al.  KIR: diverse, rapidly evolving receptors of innate and adaptive immunity. , 2002, Annual review of immunology.

[32]  L. Samelson,et al.  Signal transduction mediated by the T cell antigen receptor: the role of adapter proteins. , 2002, Annual review of immunology.

[33]  M. Poenie,et al.  Dynamic polarization of the microtubule cytoskeleton during CTL-mediated killing. , 2002, Immunity.

[34]  Mark M. Davis,et al.  Costimulation and endogenous MHC ligands contribute to T cell recognition , 2002, Nature Immunology.

[35]  J. Strominger,et al.  Signaling at the inhibitory natural killer cell immune synapse regulates lipid raft polarization but not class I MHC clustering , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[36]  T. Tan,et al.  Cell cycle regulation of c-Jun N-terminal kinase activity at the centrosomes. , 2001, Biochemical and biophysical research communications.

[37]  Leo M. Carlin,et al.  Intercellular Transfer and Supramolecular Organization of Human Leukocyte Antigen C at Inhibitory Natural Killer Cell Immune Synapses 〉 , 2001, The Journal of experimental medicine.

[38]  Michael F Denny,et al.  Superantigen-Induced T Cell:B Cell Conjugation Is Mediated by LFA-1 and Requires Signaling Through Lck, But Not ZAP-701 , 2001, The Journal of Immunology.

[39]  Z. Lou,et al.  A Role for a RhoA/ROCK/LIM-Kinase Pathway in the Regulation of Cytotoxic Lymphocytes1 , 2001, The Journal of Immunology.

[40]  J. Olivo-Marin,et al.  The membrane-microfilament linker ezrin is involved in the formation of the immunological synapse and in T cell activation. , 2001, Immunity.

[41]  G. Griffiths,et al.  The immunological synapse of CTL contains a secretory domain and membrane bridges. , 2001, Immunity.

[42]  S. Takahashi,et al.  ERM-dependent movement of CD43 defines a novel protein complex distal to the immunological synapse. , 2001, Immunity.

[43]  R. Germain,et al.  Exclusion of CD43 from the immunological synapse is mediated by phosphorylation-regulated relocation of the cytoskeletal adaptor moesin. , 2001, Immunity.

[44]  I. Mellman,et al.  Distinct patterns of membrane microdomain partitioning in Th1 and th2 cells. , 2001, Immunity.

[45]  A. Frey,et al.  CD8+ Tumor-Infiltrating T Cells Are Deficient in Perforin-Mediated Cytolytic Activity Due to Defective Microtubule-Organizing Center Mobilization and Lytic Granule Exocytosis , 2001, The Journal of Immunology.

[46]  B. Freiberg,et al.  Formation of supramolecular activation clusters on fresh ex vivo CD8+ T cells after engagement of the T cell antigen receptor and CD8 by antigen-presenting cells , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[47]  Steffen Jung,et al.  Spatial Organization of Signal Transduction Molecules in the NK Cell Immune Synapses During MHC Class I-Regulated Noncytolytic and Cytolytic Interactions , 2001, The Journal of Immunology.

[48]  Boris Barbour,et al.  Functional antigen-independent synapses formed between T cells and dendritic cells , 2001, Nature Immunology.

[49]  Adelheid Cerwenka,et al.  Natural killer cells, viruses and cancer , 2001, Nature Reviews Immunology.

[50]  A. Khoruts,et al.  Single-cell analysis of signal transduction in CD4 T cells stimulated by antigen in vivo , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[51]  L. Uharek,et al.  Activation of natural killer cells with interleukin 2 (IL‐2) and IL‐12 increases perforin binding and subsequent lysis of tumour cells , 2001, British journal of haematology.

[52]  Gerra L. Bosco,et al.  Wasp recruitment to the T cell:APC contact site occurs independently of Cdc42 activation. , 2001, Immunity.

[53]  S. Anderson,et al.  The ever‐expanding Ly49 gene family: repertoire and signaling , 2001, Immunological reviews.

[54]  D. F. Barber,et al.  Inhibition of natural killer cell activation signals by killer cell immunoglobulin‐like receptors (CD158) , 2001, Immunological reviews.

[55]  A. Kenworthy,et al.  Imaging protein-protein interactions using fluorescence resonance energy transfer microscopy. , 2001, Methods.

[56]  S. Latour,et al.  Proximal protein tyrosine kinases in immunoreceptor signaling. , 2001, Current opinion in immunology.

[57]  M. Neuberger,et al.  B cells acquire antigen from target cells after synapse formation , 2001, Nature.

[58]  Stephen P. Schoenberger,et al.  Naïve CTLs require a single brief period of antigenic stimulation for clonal expansion and differentiation , 2001, Nature Immunology.

[59]  S. Diekmann,et al.  Recent advances in FRET: distance determination in protein-DNA complexes. , 2001, Current opinion in structural biology.

[60]  Gonzalo G. Garcia,et al.  Single-Cell Analyses Reveal Two Defects in Peptide-Specific Activation of Naive T Cells from Aged Mice1 , 2001, The Journal of Immunology.

[61]  L. Machesky,et al.  Rab27a Is Required for Regulated Secretion in Cytotoxic T Lymphocytes , 2001, The Journal of cell biology.

[62]  R. Biassoni,et al.  Activating receptors and coreceptors involved in human natural killer cell-mediated cytolysis. , 2001, Annual review of immunology.

[63]  D. Yablonski,et al.  Mechanisms of signaling by the hematopoietic-specific adaptor proteins, SLP-76 and LAT and their B cell counterpart, BLNK/SLP-65. , 2001, Advances in immunology.

[64]  S. Bromley,et al.  The immunological synapse. , 2001, Annual review of immunology.

[65]  B. Zhong,et al.  Pivotal role of phosphoinositide-3 kinase in regulation of cytotoxicity in natural killer cells , 2000, Nature Immunology.

[66]  H. Lin,et al.  Signaling via LAT (linker for T-cell activation) and Syk/ZAP70 is required for ERK activation and NFAT transcriptional activation following CD2 stimulation. , 2000, Blood.

[67]  G. Crabtree,et al.  The vav exchange factor is an essential regulator in actin-dependent receptor translocation to the lymphocyte-antigen-presenting cell interface. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[68]  S. Bromley,et al.  A supramolecular basis for CD45 tyrosine phosphatase regulation in sustained T cell activation. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[69]  M. Davis,et al.  Differential clustering of CD4 and CD3zeta during T cell recognition. , 2000, Science.

[70]  C. Cabañas,et al.  Paxillin Localizes to the Lymphocyte Microtubule Organizing Center and Associates with the Microtubule Cytoskeleton* , 2000, The Journal of Biological Chemistry.

[71]  F. Beermann,et al.  Impaired Natural Killing of MHC Class I-Deficient Targets by NK Cells Expressing a Catalytically Inactive Form of SHP-11 , 2000, The Journal of Immunology.

[72]  L. Samelson,et al.  Association of Grb2, Gads, and phospholipase C-gamma 1 with phosphorylated LAT tyrosine residues. Effect of LAT tyrosine mutations on T cell angigen receptor-mediated signaling. , 2000, The Journal of biological chemistry.

[73]  N. Schmitz,et al.  Impaired binding of perforin on the surface of tumor cells is a cause of target cell resistance against cytotoxic effector cells. , 2000, Blood.

[74]  C. Cabañas,et al.  The Tyrosine Kinase Pyk-2/Raftk Regulates Natural Killer (Nk) Cell Cytotoxic Response, and Is Translocated and Activated upon Specific Target Cell Recognition and Killing , 2000, The Journal of cell biology.

[75]  A. Weiss,et al.  Signal transduction by the TCR for antigen. , 2000, Current opinion in immunology.

[76]  S. Beck,et al.  Plasticity in the organization and sequences of human KIR/ILT gene families. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[77]  J. Wehland,et al.  Fyn-Binding Protein (Fyb)/Slp-76–Associated Protein (Slap), Ena/Vasodilator-Stimulated Phosphoprotein (Vasp) Proteins and the Arp2/3 Complex Link T Cell Receptor (Tcr) Signaling to the Actin Cytoskeleton , 2000, The Journal of cell biology.

[78]  F. Vély,et al.  Signaling pathways engaged by NK cell receptors: double concerto for activating receptors, inhibitory receptors and NK cells. , 2000, Seminars in immunology.

[79]  E. Schaeffer,et al.  PKC-θ is required for TCR-induced NF-κB activation in mature but not immature T lymphocytes , 2000, Nature.

[80]  J. D. Di Santo,et al.  Tyrosine kinase SYK: essential functions for immunoreceptor signalling. , 2000, Immunology today.

[81]  L. Samelson,et al.  The role of membrane-associated adaptors in T cell receptor signalling. , 2000, Seminars in immunology.

[82]  P. Más,et al.  A novel functional interaction between Vav and PKCtheta is required for TCR-induced T cell activation. , 2000, Immunity.

[83]  Z. Lou,et al.  A Balance between Positive and Negative Signals in Cytotoxic Lymphocytes Regulates the Polarization of Lipid Rafts during the Development of Cell-Mediated Killing , 2000, The Journal of experimental medicine.

[84]  É. Vivier,et al.  Early signaling via inhibitory and activating NK receptors. , 2000, Human immunology.

[85]  L. Lanier,et al.  NK cell activation: distinct stimulatory pathways counterbalancing inhibitory signals. , 2000, Human immunology.

[86]  O. Mandelboim,et al.  The human natural killer cell immune synapse. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[87]  K. Siminovitch,et al.  Antigen Receptor–Induced Activation and Cytoskeletal Rearrangement Are Impaired in Wiskott-Aldrich Syndrome Protein–Deficient Lymphocytes , 1999, The Journal of experimental medicine.

[88]  R. Hynes,et al.  The Talin Head Domain Binds to Integrin β Subunit Cytoplasmic Tails and Regulates Integrin Activation* , 1999, The Journal of Biological Chemistry.

[89]  P. Marrack,et al.  Live cell fluorescence imaging of T cell MEKK2: redistribution and activation in response to antigen stimulation of the T cell receptor. , 1999, Immunity.

[90]  A Steinle,et al.  Activation of NK cells and T cells by NKG2D, a receptor for stress-inducible MICA. , 1999, Science.

[91]  Jun Wu,et al.  An activating immunoreceptor complex formed by NKG2D and DAP10. , 1999, Science.

[92]  S. Bromley,et al.  The immunological synapse: a molecular machine controlling T cell activation. , 1999, Science.

[93]  G. Koretzky,et al.  NK cytokine secretion and cytotoxicity occur independently of the SLP‐76 adaptor protein , 1999, European journal of immunology.

[94]  S. Tangye,et al.  Cutting edge: human 2B4, an activating NK cell receptor, recruits the protein tyrosine phosphatase SHP-2 and the adaptor signaling protein SAP. , 1999, Journal of immunology.

[95]  R. Abraham,et al.  Functional analysis of LAT in TCR-mediated signaling pathways using a LAT-deficient Jurkat cell line. , 1999, International immunology.

[96]  Y. Chien,et al.  Visualizing lymphocyte recognition , 1999, Immunology and cell biology.

[97]  R. Abraham,et al.  Cutting edge: a role for the adaptor protein LAT in human NK cell-mediated cytotoxicity. , 1999, Journal of immunology.

[98]  J. Miller,et al.  TCR, LFA-1, and CD28 play unique and complementary roles in signaling T cell cytoskeletal reorganization. , 1999, Journal of immunology.

[99]  A. Lanzavecchia,et al.  T lymphocyte costimulation mediated by reorganization of membrane microdomains. , 1999, Science.

[100]  C. Rudd Adaptors and Molecular Scaffolds in Immune Cell Signaling , 1999, Cell.

[101]  J. Coligan,et al.  Specific recognition of HLA-E, but not classical, HLA class I molecules by soluble CD94/NKG2A and NK cells. , 1999, Journal of immunology.

[102]  C. Biron,et al.  Natural killer cells in antiviral defense: function and regulation by innate cytokines. , 1999, Annual review of immunology.

[103]  G. Koretzky,et al.  Integration of T cell receptor-dependent signaling pathways by adapter proteins. , 1999, Annual review of immunology.

[104]  W Carrington,et al.  Digital imaging microscopy of living cells. , 1998, Trends in cell biology.

[105]  F. Sánchez‐Madrid,et al.  Roles of chemokines and receptor polarization in NK-target cell interactions. , 1998, Journal of immunology.

[106]  Patricia L. Widder,et al.  A Novel Adaptor Protein Orchestrates Receptor Patterning and Cytoskeletal Polarity in T-Cell Contacts , 1998, Cell.

[107]  Colin R. F. Monks,et al.  Three-dimensional segregation of supramolecular activation clusters in T cells , 1998, Nature.

[108]  D. Cantrell,et al.  GTPases in antigen receptor signalling. , 1998, Current opinion in immunology.

[109]  A. Weiss,et al.  Cytoskeletal Polarization of T Cells Is Regulated by an Immunoreceptor Tyrosine-based Activation Motif–dependent Mechanism , 1998, The Journal of cell biology.

[110]  J. Bell,et al.  HLA-E binds to natural killer cell receptors CD94/NKG2A, B and C , 1998, Nature.

[111]  L. Lanier NK cell receptors. , 1998, Annual review of immunology.

[112]  P. Leibson,et al.  Signal transduction during NK cell activation: balancing opposing forces. , 1998, Current topics in microbiology and immunology.

[113]  P. Leibson,et al.  Functional Role for Syk Tyrosine Kinase in Natural Killer Cell–mediated Natural Cytotoxicity , 1997, The Journal of experimental medicine.

[114]  T. Kurosaki,et al.  Molecular mechanisms in B cell antigen receptor signaling. , 1997, Current opinion in immunology.

[115]  Eric O Long,et al.  A single amino acid in the p58 killer cell inhibitory receptor controls the ability of natural killer cells to discriminate between the two groups of HLA-C allotypes. , 1997, Journal of immunology.

[116]  S. Lev,et al.  Tyrosine Phosphorylation of Pyk2 Is Selectively Regulated by Fyn During TCR Signaling , 1997, The Journal of experimental medicine.

[117]  B. Druker,et al.  RAFTK, a Novel Member of the Focal Adhesion Kinase Family, Is Phosphorylated and Associates with Signaling Molecules upon Activation of Mature T Lymphocytes , 1997, The Journal of experimental medicine.

[118]  C. Figdor,et al.  Dual role of the actin cytoskeleton in regulating cell adhesion mediated by the integrin lymphocyte function-associated molecule-1. , 1997, Molecular biology of the cell.

[119]  M. Reth,et al.  Initiation and processing of signals from the B cell antigen receptor. , 1997, Annual review of immunology.

[120]  J. Kinet,et al.  Sequential involvement of Lck and SHP-1 with MHC-recognizing receptors on NK cells inhibits FcR-initiated tyrosine kinase activation. , 1996, Immunity.

[121]  P. Parham,et al.  Killer Cell Inhibitory Receptor Recognition of Human Leukocyte Antigen (HLA) Class I Blocks Formation of a pp36/PLC-γ Signaling Complex in Human Natural Killer (NK) Cells , 1996, The Journal of experimental medicine.

[122]  A. Fauci,et al.  Human CD8+ T lymphocyte subsets that express HLA class I-specific inhibitory receptors represent oligoclonally or monoclonally expanded cell populations. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[123]  L. Lanier,et al.  Phosphotyrosines in the killer cell inhibitory receptor motif of NKB1 are required for negative signaling and for association with protein tyrosine phosphatase 1C , 1996, The Journal of experimental medicine.

[124]  M. Colonna,et al.  Tyrosine phosphorylation of a human killer inhibitory receptor recruits protein tyrosine phosphatase 1C , 1996, The Journal of experimental medicine.

[125]  D. Cantrell,et al.  T cell antigen receptor signal transduction pathways. , 1996, Annual review of immunology.

[126]  S. Ley,et al.  Interactions between the Protein-tyrosine Kinase ZAP-70, the Proto-oncoprotein Vav, and Tubulin in Jurkat T Cells (*) , 1995, The Journal of Biological Chemistry.

[127]  A. Weiss,et al.  The Syk/ZAP-70 protein tyrosine kinase connection to antigen receptor signalling processes. , 1995, Seminars in immunology.

[128]  P. Parham,et al.  Superantigen-dependent, cell-mediated cytotoxicity inhibited by MHC class I receptors on T lymphocytes. , 1995, Science.

[129]  P. Parham,et al.  The Bw4 public epitope of HLA-B molecules confers reactivity with natural killer cell clones that express NKB1, a putative HLA receptor , 1995, The Journal of experimental medicine.

[130]  G. Trinchieri,et al.  The role of natural killer cells in host-parasite interactions. , 1995, Current opinion in immunology.

[131]  P. Parham,et al.  NKB1: a natural killer cell receptor involved in the recognition of polymorphic HLA-B molecules , 1994, The Journal of experimental medicine.

[132]  S. Ley,et al.  Distinct intracellular localization of Lck and Fyn protein tyrosine kinases in human T lymphocytes , 1994, The Journal of cell biology.

[133]  V. Stewart,et al.  RAG-2-deficient mice lack mature lymphocytes owing to inability to initiate V(D)J rearrangement , 1992, Cell.

[134]  Susumu Tonegawa,et al.  RAG-1-deficient mice have no mature B and T lymphocytes , 1992, Cell.

[135]  R. Abraham,et al.  Tyrosine phosphorylation provides an early and requisite signal for the activation of natural killer cell cytotoxic function. , 1991, Proceedings of the National Academy of Sciences of the United States of America.

[136]  B. Sefton,et al.  Protein tyrosine phosphorylation is induced in murine B lymphocytes in response to stimulation with anti‐immunoglobulin. , 1990, The EMBO journal.

[137]  H. Ljunggren,et al.  In search of the 'missing self': MHC molecules and NK cell recognition. , 1990, Immunology today.

[138]  M. Reth Antigen receptor tail clue , 1989, Nature.

[139]  S. Singer,et al.  The specific direct interaction of helper T cells and antigen- presenting B cells. II. Reorientation of the microtubule organizing center and reorganization of the membrane-associated cytoskeleton inside the bound helper T cells , 1987, The Journal of experimental medicine.