Señalización diferencial en células T mutantes en TCR[beta] resistentes a apoptosis : estudio de intermediarios tempranos y tardíos

En esta tesis hemos tratado de profundizar en los mecanismos que hacen al TCR capaz de señalizar diferencialmente. El receptor mutante en la transmembrana de TCRB es capaz de soportar algunas respuestas de la célula T pero es incapaz de inducir otras. Asi, hemos demostrado que (1) a traves de la estimulación del TCRB mutante se diseccionan las señales que median la apoptosis (FasL) frente a las que median la proliferación y secreción de citoquinas (IL-2, IFNy, TNFa). (2) Los mecanismos que soportan el fenotipo funcional de las células mutantes se han podido adscribir a alteraciones bioquimicas seriadas, tanto a nivel de intermediarios tempranos como tardios. (3) El TCR mutante diversifica las rutas de señalización desde los eventos más tempranos de la señal y lo hace modulando tanto la actividad de intermediarios mediante la fosforilación Tyr como la ubicación de los mismos en distintos compartimentos celulares. (4) Tras estimulacion del recepotr mutante en TCRB se ven afectadas las señales que conducen a la activación de NF-kB y de MAPKs, mientras que la induccion de NF-AT permanece intacta. Además, la mutación en el dominio transmembrana de TCRB tiene importantes consecuencias para la biología de la celula T, y en concreto, para el fenomeno apoptotico puesto que las celulas mutantes son resistentes a la apoptosis inducida a través de su TCR. El sistema experimental ha permitido (1) Demostrar que NF-kB es esencial para la regulación transcripcional de FasL, habiendo sido identificado un sitio funcionalmente activo en el promotor de dicha molécula inductora de muerte. (2) Sugerir que JNK podrian estar involucradas en la regulación temprana de la inducción de FasL de modo que deficiencias en las rutas de activación de NF-kB, JNK y p38MAPK podrian explicar la resistencia apoptótica en las celulas mutante

A Novel Functional Interaction between Vav and PKCθ Is Required for TCR-Induced T Cell Activation

AbstractVav and PKCθ play an early and important role in the TCR/CD28-induced stimulation of MAP kinases and activation of the IL-2 gene. Vav is also essential for actin cytoskeleton reorganization and TCR capping. Here, we report that PKCθ function was selectively required in a Vav signaling pathway that mediates the TCR/CD28-induced activation of JNK and the IL-2 gene and the upregulation of CD69 expression. Vav also promoted PKCθ translocation from the cytosol to the membrane and cytoskeleton and induced its enzymatic activation in a CD3/CD28-initiated pathway that was dependent on Rac and on actin cytoskeleton reorganization. These findings reveal that the Vav/Rac pathway promotes the recruitment of PKCθ to the T cell synapse and its activation, essential processes for T cell activation and IL-2 production

Interplay of Inflammatory, Antigen and Tissue-Derived Signals in the Development of Resident CD8 Memory T Cells

CD8 positive, tissue resident memory T cells (TRM) are a specialized subset of CD8 memory T cells that surveil tissues and provide critical first-line protection against tumors and pathogen re-infection. Recently, much effort has been dedicated to understanding the function, phenotype and development of TRM. A myriad of signals is involved in the development and maintenance of resident memory T cells in tissue. Much of the initial research focused on the roles tissue-derived signals play in the development of TRM, including TGFß and IL-33 which are critical for the upregulation of CD69 and CD103. However, more recent data suggest further roles for antigenic and pro-inflammatory cytokines. This review will focus on the interplay of pro-inflammatory, tissue and antigenic signals in the establishment of resident memory T cells

Tracking cryptic SARS-CoV-2 Lineages Detected in NYC Wastewater

Tracking SARS-CoV-2 genetic diversity is strongly indicated because diversifying selection may lead to the emergence of novel variants resistant to naturally acquired or vaccine-induced immunity. To monitor New York City (NYC) for the presence of novel variants, we deep sequence most of the receptor binding domain coding sequence of the S protein of SARS-CoV-2 isolated from the New York City wastewater. Here we report detecting increasing frequencies of novel cryptic SARS-CoV-2 lineages not recognized in GISAID’s EpiCoV database. These lineages contain mutations that had been rarely observed in clinical samples, including Q493K, Q498Y, E484A, and T572N and share many mutations with the Omicron variant of concern. Some of these mutations expand the tropism of SARS-CoV-2 pseudoviruses by allowing infection of cells expressing the human, mouse, or rat ACE2 receptor. Finally, pseudoviruses containing the spike amino acid sequence of these lineages were resistant to different classes of receptor binding domain neutralizing monoclonal antibodies. We offer several hypotheses for the anomalous presence of these lineages, including the possibility that these lineages are derived from unsampled human COVID-19 infections or that they indicate the presence of a non-human animal reservoir

Low-Affinity T Cells Are Programmed to Maintain Normal Primary Responses but Are Impaired in Their Recall to Low-Affinity Ligands

T cell responses to low-affinity T cell receptor (TCR) ligands occur in the context of infection, tumors, and autoimmunity despite diminished TCR signal strength. The processes that enable such responses remain unclear. We show that distinct mechanisms drive effector/memory development in high- and low-affinity T cells. Low-affinity cells preferentially differentiate into memory precursors of a central memory phenotype that are interleukin (IL)-12Rlo, IL-7Rhi, and Eomeshi. Strikingly, in contrast to naive cells, low-affinity memory cells were impaired in the response to low- but not high-affinity ligands, indicating that low-affinity cells are programmed to generate diverse immune responses while avoiding autoreactivity. Affinity and antigen dose directly correlated with IL-12R signal input and T-bet but not with Eomes expression because low- affinity signals were more potent inducers of Eomes at a high antigen dose. Our studies explain how weak antigenic signals induce complete primary immune responses and provide a framework for therapeutic intervention

Different T cell receptor signals determine CD8+ memory versus effector development

Following infection, naïve CD8+ T cells bearing pathogen-specific T cell receptors (TCRs) differentiate into a mixed population of short-lived effector and long-lived memory T cells to mediate an adaptive immune response. How the TCR regulates memory T cell development has remained elusive. Using a mutant TCR transgenic model, we found that point mutations in the TCR beta transmembrane domain (betaTMD) impair the development and function of CD8+ memory T cells without affecting primary effector T cell responses. Mutant T cells are deficient in polarizing the TCR and in organizing the nuclear factor kappaB signal at the immunological synapse. Thus, effector and memory states of CD8+ T cells are separable fates, determined by differential TCR signaling