CXCL13 as an aging-associated defect in memory T cell homeostasis

Project Summary/Abstract
Aging is associated with dramatically increased susceptibility to infectious diseases like influenza. Although
vaccination is the primary strategy for minimizing flu deaths, older adults have consistently impaired vaccine
responses. Preliminary analyses of tonsil T cells from older vs younger adults reveal that CXCL13 is
significantly decreased in old follicular helper T cells as compared to young. Further preliminary experiments in
tonsil organoids reveal a role for CXCL13 in memory CD4+ T cell homeostasis. While CXCL13 is expressed by
follicular helper T cells in humans, mouse T cells lack CXCL13 expression entirely. The Research Strategy
proposed here will leverage human immune organoid technology, developed in sponsor Dr. Mark Davis’ lab, to
define the role of CXCL13 as an aging-associated defect in memory T cell homeostasis. This work will reveal
the mechanism of CXCL13-mediated maintenance of memory T cells (Aim 1) and define the identity of the T
cell pool that is maintained by CXCL13 (Aim 2). In Aim 1, the applicant Dr. Casey Beppler will use CRISPR-
engineered CXCL13-KO tonsil organoids, specific cell type depletions, and single cell RNA sequencing to
reveal the cellular and molecular mediators of CXCL13-mediated T cell homeostasis. In Aim 2, Dr. Beppler will
integrate cellular phenotyping of human tonsil and spleen T cells across adult lifespan with spheromer staining
of antigen-specific T cells (also developed in the Davis Lab) in CXCL13-KO tonsil organoids to determine the
specific T cell population that is maintained by CXCL13. Although work proposed here will focus on the role of
CXCL13 in secondary lymphoid organs, these findings are likely to reveal mechanisms at play in tertiary
lymphoid structures across disease states from cancer to autoimmunity. The research and career development
training plans are tailored to enable Dr. Beppler to gain new skills in modeling human lymphoid tissues with
immune organoids and single cell RNA sequencing, as well as professional development skills in mentoring,
oral presentation, and grant writing. Sponsor Dr. Mark Davis is a long-standing expert in the field of antigen-
specific T cell responses and a leader in human systems immunology. Advisors will contribute with their
complementary expertise: Dr. Purvesh Khatri (bioinformatics), Dr. Le Cong (CRISPR and gene editing), and Dr.
Bali Pulendran (multi-omics analysis of human immune responses). The Stanford Institute for Immunity,
Transplantation & Infection directed by Dr. Davis is an excellent environment for collaborative and cutting-edge
research, supported by outstanding infrastructure (Stanford Center for Genomics, Human Immune Monitoring
Center). In summary, the strong mentorship and training plan will prepare Dr. Beppler for her future
independent career studying human T cell immunology. This project will improve our understanding of an
aging-associated defect in human lymphoid tissues, thus providing the potential for future therapies to promote
memory homeostasis and limiting the number of deaths to vaccine-preventable diseases.

Grant Number: 5F32AI186256-02
NIH Institute/Center: NIH
Principal Investigator: Casey Beppler