Goronzy, Jörg J.

Abstract Generation of a protective and long-lasting immune memory is central to effective vaccination strategies and healthy aging. However, age-associated changes in immune cells, particularly T cells, impair immune memory generation and maintenance rendering older adults vulnerable to infectious diseases. Here, we investigated signatures of age-related memory T cell dysfunction and uncovered molecular determinants of a protective, persistent T cell memory in older individuals. We leveraged the contrasting T cell memory elicited in younger (<30 years) and older adults (>55 years) by vaccination against varicella zoster virus (VZV). Using ex vivo peptide stimulation of peripheral blood mononuclear cells of vaccine recipients several years after vaccination, we collected antigen-specific CD4+ and CD8+ T cells for high-dimensional spectral flow cytometry and tri-modal single-cell sequencing analyses. We found that older vaccine recipients predominantly suffer from a quantitatively and qualitatively impaired CD8+ T cell memory response compared to younger adults receiving the same vaccine type. Conversely, comparisons of two VZV vaccine strategies with contrasting efficacies in older adults demonstrated that a CD4+ T cell response rich in self-renewing Th17-like and low in regulatory T cells overcomes the age-associated T cell memory defect and associates with a durable, protective T cell memory. Collectively, we propose that vaccine strategies targeted towards older adults benefit from a Th17-focused CD4+ T cell memory response. Our results not only uncover traits of immune cell dysfunction with aging, but also inform vaccination efforts tailored towards healthy aging.

Abstract The Midwest Aging Consortium (MAC) has emerged as a critical collaborative initiative aimed at advancing our understanding of aging and developing strategies to combat the rising prevalence of age-related diseases. Founded in 2019, MAC brings together researchers from various disciplines and institutions across the Midwestern United States to foster interdisciplinary geroscience research. This report summarizes the highlights of the Fourth Annual Symposium of MAC, which was held at Iowa State University in May 2023. The symposium featured presentations on a wide array of topics, including studies on slow-aging animals, cellular senescence and senotherapeutics, the role of the immune system in aging, metabolic changes in aging, neuronal health in aging, and biomarkers for measuring the aging process. Speakers shared findings from studies involving a variety of animals, ranging from commonly used species such as mice, rats, worms, yeast, and fruit flies, to less-common ones like naked mole-rats, painted turtles, and rotifers. MAC continues to emphasize the importance of supporting emerging researchers and fostering a collaborative environment, positioning itself as a leader in aging research. This symposium not only showcased the current state of aging biology research but also highlighted the consortium’s role in training the next generation of scientists dedicated to improving the healthspan and well-being of the aging population.

IgG4-related disease (IgG4-RD) is a systemic immune-mediated fibroinflammatory disease whose pathomechanisms remain poorly understood. Here, we identified gene variants in familial IgG4-RD and determined their functional consequences. All 3 affected members of the family shared variants of the transcription factor IKAROS, encoded by IKZF1 , and the E3 ubiquitin ligase UBR4. The IKAROS variant increased binding to the FYN promoter, resulting in higher transcription of FYN in T cells. The UBR4 variant prevented the lysosomal degradation of the phosphatase CD45. In the presence of elevated FYN, CD45 functioned as a positive regulatory loop, lowering the threshold for T cell activation. Consequently, T cells from the affected family members were hyperresponsive to stimulation. When transduced with a low-avidity, autoreactive T cell receptor, their T cells responded to the autoantigenic peptide. In parallel, high expression of FYN in T cells biased their differentiation toward Th2 polarization by stabilizing the transcription factor JunB. This bias was consistent with the frequent atopic manifestations in patients with IgG4-RD, including the affected family members in the present study. Building on the functional consequences of these 2 variants, we propose a disease model that is not only instructive for IgG4-RD but also for atopic diseases and autoimmune diseases associated with an IKZF1 risk haplotype.

The human adult immune system maintains normal T cell counts and compensates for T cell loss throughout life, mainly through peripheral homeostatic proliferation after the ability of the thymus to generate new T cells has rapidly declined at adolescence. This process is mainly driven by STAT5-activating cytokines, most importantly IL-7, and is very effective in maintaining a large naive CD4 + T cell compartment into older age. Here, we describe that naive CD4 + T cells undergo adaptations to optimize IL-7 responses by upregulating the guanine-nucleotide exchange factor PREX1 in older age. PREX1 promotes nuclear translocation of phosphorylated STAT5, thereby supporting homeostatic proliferation in response to IL-7. Through the same mechanism, increased expression of PREX1 also biases naive cells to differentiate into effector T cells. These findings are consistent with the concept that primarily beneficial adaptations during aging, i.e., improved homeostasis, account for unfavorable functions of the aged immune system, in this case biased differentiation.

Autoimmune vasculitis of the medium and large elastic arteries can cause blindness, stroke, aortic arch syndrome, and aortic aneurysm. The disease is often refractory to immunosuppressive therapy and progresses over decades as smoldering aortitis. How the granulomatous infiltrates in the vessel wall are maintained and how tissue-infiltrating T cells and macrophages are replenished are unknown. Single-cell and whole-tissue transcriptomic studies of immune cell populations in vasculitic arteries identified a CD4 + T cell population with stem cell–like features. CD4 + T cells supplying the tissue-infiltrating and tissue-damaging effector T cells survived in tertiary lymphoid structures around adventitial vasa vasora, expressed the transcription factor T cell factor 1 (TCF1), had high proliferative potential, and gave rise to two effector populations, Eomesodermin (EOMES) + cytotoxic T cells and B cell lymphoma 6 (BCL6) + T follicular helper-like cells. TCF1 hi CD4 + T cells expressing the interleukin 7 receptor (IL-7R) sustained vasculitis in serial transplantation experiments. Thus, TCF1 hi CD4 + T cells function as disease stem cells and promote chronicity and autonomy of autoimmune tissue inflammation. Remission-inducing therapies will require targeting stem-like CD4 + T cells instead of only effector T cells.

Harnessing the immunogenic potential of senescent cells may be a viable but context-dependent opportunity to boost antitumor immunity.

Giant cell arteritis is an autoimmune disease of medium and large arteries, characterized by granulomatous inflammation of the three-layered vessel wall that results in vaso-occlusion, wall dissection, and aneurysm formation. The immunopathogenesis of giant cell arteritis is an accumulative process in which a prolonged asymptomatic period is followed by uncontrolled innate immunity, a breakdown in self-tolerance, the transition of autoimmunity from the periphery into the vessel wall and, eventually, the progressive evolution of vessel wall inflammation. Each of the steps in pathogenesis corresponds to specific immuno-phenotypes that provide mechanistic insights into how the immune system attacks and damages blood vessels. Clinically evident disease begins with inappropriate activation of myeloid cells triggering the release of hepatic acute phase proteins and inducing extravascular manifestations, such as muscle pains and stiffness diagnosed as polymyalgia rheumatica. Loss of self-tolerance in the adaptive immune system is linked to aberrant signaling in the NOTCH pathway, leading to expansion of NOTCH1 + CD4 + T cells and the functional decline of NOTCH4 + T regulatory cells (Checkpoint 1). A defect in the endothelial cell barrier of adventitial vasa vasorum networks marks Checkpoint 2; the invasion of monocytes, macrophages and T cells into the arterial wall. Due to the failure of the immuno-inhibitory PD-1 (programmed cell death protein 1)/PD-L1 (programmed cell death ligand 1) pathway, wall-infiltrating immune cells arrive in a permissive tissues microenvironment, where multiple T cell effector lineages thrive, shift toward high glycolytic activity, and support the development of tissue-damaging macrophages, including multinucleated giant cells (Checkpoint 3). Eventually, the vascular lesions are occupied by self-renewing T cells that provide autonomy to the disease process and limit the therapeutic effectiveness of currently used immunosuppressants. The multi-step process deviating protective to pathogenic immunity offers an array of interception points that provide opportunities for the prevention and therapeutic management of this devastating autoimmune disease.

Abstract Superantigens encoded in the genome or released by bacteria have been identified as potent modulators of the murine immune system. High frequencies of mature or immature T cells are activated or intrathymically deleted when superantigens cross-link MHC class II molecules and the V beta element of the TCR. The V beta specificity discriminates superantigens from polyclonal T cell stimulators as well as specific Ag and determines the immunomodulatory role in shaping the T cell repertoire. A similar regulatory function of superantigens in the human immune system is less well established. Here, we have studied a series of human T cell clones sharing the TCR V beta 6 element and describe a surprising heterogeneity in their responsiveness to staphylococcal exotoxins. The V beta 6 gene segment had the ability to respond to all staphylococcal enterotoxins (SE); however, for individual T cell clones, there was a clear predominance of SE C3 reactivity compared to SE B and SE C2. The clonal heterogeneity of SE responsiveness did not correlate to sequence polymorphisms in the fourth hypervariable region of the V beta 6 segment, the presumptive binding site for superantigens. Superantigen reactivity was crucially influenced by the presenting HLA-DR molecule, especially when the superantigen served as a coligand, enhancing or suppressing the Ag-specific activation of the TCR. These data suggest that the correlation between human TCR V beta gene segments and superantigen responses is not stringent. Potential intrathymic deletion mechanisms controlled by superantigens may be less selective in humans and may result in a leakiness influenced by the host HLA-DR molecules.

Abstract The costimulatory molecule CD28 has a restricted tissue distribution and is expressed on T cells and some plasmacytoma cells. Although CD28 is constitutively expressed, its expression is transiently down-regulated following T cell activation and declines progressively with in vitro senescence. In vivo, CD8+ T cells and, less frequently, CD4+ T cells may completely lose CD28 surface expression during chronic infections and with aging. This correlates with changes of nuclear protein-binding activities to two motifs, site α and β, within the CD28 minimal promoter. Both α- and β-bound complexes are found only in lymphoid tissues, in CD28+ T cells, and in some transformed B cells. These complexes are coordinately expressed except during replicative senescence, which is characterized by the down-modulation of site β- but not site α-binding activities. In contrast, T cell activation induces a parallel decline in both site α- and β-binding activities. CD4+ and CD8+ T cells differ in their β-binding profiles, which may explain the more pronounced down-regulation of CD28 in senescent CD8+ T cells. In vivo expanded CD4+CD28null and CD8+CD28null T cells uniformly lack α- and β-bound complexes, resembling the pattern seen in chronically activated cells and not of senescent cells.

Abstract In rheumatoid synovitis, lymphocytes can be arranged in follicular structures resembling secondary lymphoid follicles. To understand the organizing principles of this ectopic lymphoid tissue, the cellular components contributing to synovial follicles were examined. In 9 of 24 synovial tissue biopsies, lymphoid aggregates were found consisting of CD4+ T cells and CD20+ B cells. In four of the nine patients, the follicular centers were occupied by CD23+ CD21+ cellular networks representing follicular dendritic cells involved in germinal center reactions. In five patients, CD23+ cells were absent from the centers of the aggregates, suggesting that fully developed germinal centers are generated in only a subset of patients. To identify factors involved in the regulation of the synovial microarchitecture, cell populations contributing to the follicles were quantified by digital image analysis of immunostained tissue and by flow cytometry of tissue-derived lymphocytes. Proportions of CD4+, CD20+, and CD68+ cell subsets were surprisingly invariant, irrespective of the presence or absence of CD23+ follicular dendritic cells. Instead, tissue biopsies with CD23+ germinal center-like regions could be distinguished from those with CD23− T cell-B cell aggregates by a fourfold increase in the frequency of tissue-infiltrating CD8+ T cells, a fraction of which expressed CD40 ligand (CD40L). The data suggest a previously unsuspected role of CD8+ lymphocytes in modulating germinal center formation and raise the possibility that CD8+ CD40L+ T cells are involved in aggravating pathologic immune responses in rheumatoid synovitis.