SLAMF7 selectively favors degranulation to promote cytotoxicity in human NK cells.

NK cells play an important role in immunity by recognizing and eliminating cells undergoing infection or malignant transformation. This role is dependent on the ability of NK cells to lyse targets cells in a perforin-dependent mechanism and by secreting inflammatory cytokines. Both effector functions are controlled by several cell surface receptors. The Signaling Lymphocyte Activation Molecule (SLAM) family of receptors plays an essential role in regulating NK cell activation. Several studies have demonstrated that SLAMF7 regulates NK cell activation. However, the molecular and cellular mechanisms by which SLAMF7 influences NK effector functions are unknown. Here, we present evidence that physiological ligation of SLAMF7 in human NK cells enhances the lysis of target cells expressing SLAMF7. This effect was dependent on the ability of SLAMF7 to promote NK cell degranulation rather than cytotoxic granule polarization or cell adhesion. Moreover, SLAMF7-dependent NK cell degranulation was predominantly dependent on PLC-γ when compared to PI3K. These data provide novel information on the cellular mechanism by which SLAMF7 regulates human NK cell activation. Finally, this study supports a model for NK cell activation where activated receptors contribute by regulating specific discrete cellular events rather than multiple cellular processes.

[Anything that can go wrong: cytotoxic cells and their control of Epstein-Barr virus]. / Si algo puede fallar: las células citotóxicas en la contención del virus Epstein-Barr.

Epstein-Barr virus (EBV) is an gamma of herpes virus affecting exclusively humans, was the first oncogenic virus described and is associated with over seven different cancers. Curiously, the exchange of genes during viral infections has enabled the evolution of other cellular organisms, favoring new functions and the survival of the host. EBV has been co-evolving with mammals for hundreds of millions of years, and more than 95% of adults have been infected in one moment of their life. The infection is acquired primarily during childhood, in most cases as an asymptomatic infection. However, during adolescence or young adulthood, around 10 to 30% develop infectious mononucleosis. The NK and CD8+ T cells are the cytotoxic cells of the immune system that focus on antiviral responses. Importantly, an essential role of NK and CD8+ T cells has been demonstrated during the control and elimination of EBV-infected cells. Nonetheless, when the cytotoxic function of these cells is compromised, the infection increases the risk of developing lymphoproliferative diseases and cancer, often fatal. In this review, we delineate EBV infection and the importance of cytotoxic responses by NK and CD8+ T cells during the control and elimination of EBV-infected cells. Furthermore, we briefly discuss the main inborn errors of immunity that compromise cytotoxic responses by NK and CD8+ T cells, and how this scenario affects the antiviral response during EBV infection. Finally, we conclude the review by underlying the need for an effective EBV vaccine capable of preventing infection and the consequent development of malignancies and autoimmune diseases.

El virus Epstein-Barr es una variante del herpes virus que afecta exclusivamente a humanos; fue el primer virus oncogénico descrito y se ha relacionado con más de siete diferentes tipos de cáncer. Curiosamente, el intercambio de genes debido a infecciones virales ha permitido la evolución de los organismos celulares, favoreciendo el desarrollo de nuevas funciones y supervivencia del hospedero. El virus Epstein-Barr comparte cientos de millones de años de coevolución con la especie humana y más del 95% de la población adulta mundial se ha infectado en algún momento de su vida. La infección se adquiere principalmente durante la infancia, y en la mayoría de los casos aparece sin ninguna manifestación grave aparente. Sin embargo, en los adolescentes y la población joven-adulta, alrededor de un 10 a 30% evolucionan a mononucleosis infecciosa. Las células NK y T CD8+ son células citotóxicas cruciales durante las respuestas antivirales y se ha demostrado que que controlan y eliminan la infección por el virus Epstein-Barr. No obstante, cuando se afecta su función efectora, el desenlace puede ser fatal. El objetivo de esta revisión es describir la infección por el virus Epstein-Barr y el papel decisivo de las células NK y T CD8+ durante el control y eliminación de la infección. Además, se discuten brevemente los principales defectos genéticos que afectan a estas células y conllevan a la incapacidad para eliminar el virus. Finalmente, se resalta la necesidad de elaborar una vacuna efectiva contra el virus Epstein-Barr y cómo podrían evitarse los procesos neoplásicos y enfermedades autoinmunes.