ICAM-1 depletion in the center of immunological synapses is important for calcium releasing in T-cells

T-cell activation requires the formation of the immunological sy napse(IS)bet ween a T-cll and anantigen-presenting cell(AP C)to control the development of the adaptive immune response.How-ever,calcium release,an initial signal of T-cell activation,has been found to occur before IS for-mation.The mechanism for triggering the calcium signaling and relationship bet ween calciumrelease and IS format ion remains unclear.Herein,using live-cell imaging,we found that int ercellularadhesion molecule 1(ICAM-1),an essential mdlecule for IS formation,accumulated and then wasdepleted at the center of the synapse before complete IS formation.During the proces of ICAM1depletion,calcium was released.if ICAM-1 failed to be depleted from the center of the synapse,thesustained calcium signaling could not be induced.Moreover,depletion of ICAM-1 in ISs preferen-tially ccurred with the contact of antigen-specific T-cels and dendritic clls(DCs).Blocking thebinding ofICA M-1 and lymphocy te finction-associated antigen 1(LFA-1),ICAM-1 failed to depleteat the center of the synapse,and calcium release in T-clls decreased.In studying the mechanism ofhow the depletion ofiCA M1 could influence calcium release in T-clls,we found that the movementof ICAM-1 was associat ed with the localization of LFA-1 in the IS,which afected the localization ofcalcium microdomains,ORAIl and mitochondria in IS.Therefore,the depletion of ICAM-1 in the center of the synapse is an important factor for an initial sust ained calcium release in T-cells.

Chimeric antigen receptor （CAR）-modified natural killer cell-based immunotherapy and immunological synapse formation in cancer and HIV

Cytotoxic T lymphocytes （CTLs） and natural killer （NK） cells contribute to the body＇s immune defenses. Current chimeric antigen receptor （CAR）-modified T cell immunotherapy shows strong promise for treating var- ious cancers and infectious diseases. Although CAR- modified NK cell immunotherapy is rapidly gaining attention, its clinical applications are mainly focused on preclinical investigations using the NK92 cell line. Despite recent advances in CAR-modified T cell immunotherapy, cost and severe toxicity have hindered its widespread use. To alleviate these disadvantages of CAR-modified T cell immunotherapy, additional cyto- toxic cell-mediated immunotherapies are urgently nee- ded. The unique biology of NK cells allows them to serve as a safe, effective, alternative immunotherapeutic strategy to CAR-modified T cells in the clinic. While the fundamental mechanisms underlying the cytotoxicity and side effects of CAR-modified T and NK cell immunotherapies remain poorly understood, the for- mation of the immunological synapse （IS） between CAR- modified T or NK cells and their susceptible target cells is known to be essential. The role of the IS in CAR T and NK cell immunotherapies will allow scientists to harness the power of CAR-modified T and NK cells to treat can- cer and infectious diseases. In this review, we highlight the potential applications of CAR-modified NK cells to treat cancer and human immunodeficiency virus （HIV）, and discuss the challenges and possible future directions of CAR-modified NK cell immunotherapy, as well as the importance of understanding the molecular mechanisms of CAR-modified T cell- or NK cell-medi- ated cytotoxicity and side effects, with a focus on the CAR-modified NK cell IS.

Signaling from T cell receptors (TCRs) and chimeric antigen receptors (CARs) on T cells

T cells react to foreign or self-antigens through T cell receptor(TCR)signaling.Several decades of research have delineated the mechanism of TCR signal transduction and its impact on T cell performance.This knowledge provides the foundation for chimeric antigen receptor T cell(CAR-T cell)technology,by which T cells are redirected in a major histocompatibility complex-unrestricted manner.TCR and CAR signaling plays a critical role in determining the T cell state,including exhaustion and memory.Given its artificial nature,CARs might affect or rewire signaling differently than TCRs.A better understanding of CAR signal transduction would greatly facilitate improvements to CAR-T cell technology and advance its usefulness in clinical practice.Herein,we systematically review the knowns and unknowns of TCR and CAR signaling,from the contact of receptors and antigens,proximal signaling,immunological synapse formation,and late signaling outcomes.Signaling through different T cell subtypes and how signaling is translated into practice are also discussed.

NK cell detachment from target cells is regulated by successful cytotoxicity and influences cytokine production

Natural killer(NK)cells participate in early immune defenses against pathogens and tumors and play a major role as immune effector and regulatory cells.The NK cell-mediated elimination of an infected or cancerous cell is a highly regulated process that requires the formation of a cell contact,the establishment of an immunological synapse and the polarization and release of lytic granules.Additionally,the detachment of NK cells from target cells is important for NK cells to bind and kill other cells in a process called serial killing.However,very little is known about this detachment process.Here,we show that NK detachment is directly connected to the successful killing of a target cell.The inhibition of killing due to reduced NK cell cytotoxicity or increased target cell resistance results in defective detachment and prolonged contact times.This effect leads to sustained Ca^(2+) flux in NK cells and the hypersecretion of proinflammatory cytokines.Linking defective cytotoxicity with enhanced cytokine secretion via reduced detachment may explain inflammatory pathologies in several diseases.