Peripheral blood T-cell signatures from high-resolution immune phenotyping of γδ and αβ T-cells in younger and older subjects in the Berlin Aging Study II

Background Aging and latent infection with Cytomegalovirus (CMV) are thought to be major factors driving the immune system towards immunosenescence, primarily characterized by reduced amounts of naïve T-cells and increased memory T-cells, potentially associated with higher morbidity and mortality. The composition of both major compartments, γδ as well as αβ T-cells, is altered by age and CMV, but detailed knowledge of changes to the γδ subset is currently limited. Results Here, we have surveyed a population of 73 younger (23–35 years) and 144 older (62–85 years) individuals drawn from the Berlin Aging Study II, investigating the distribution of detailed differentiation phenotypes of both γδ and αβ T-cells. Correlation of frequencies and absolute counts of the identified phenotypes with age and the presence of CMV revealed a lower abundance of Vδ2-positive and a higher amount of Vδ1-positive cells. We found higher frequencies of late-differentiated and lower frequencies of early-differentiated cells in the Vδ1+ and Vδ1-Vδ2-, but not in the Vδ2+ populations in elderly CMV-seropositive individuals confirming the association of these Vδ2-negative cells with CMV-immunosurveillance. We identified the highest Vδ1:Vδ2 ratios in the CMV-seropositive elderly. The observed increased CD4:CD8 ratios in the elderly were significantly lower in CMV-seropositive individuals, who also possessed a lower naïve and a larger late-differentiated compartment of CD8+ αβ T-cells, reflecting the consensus in the literature. Conclusions Our findings illustrate in detail the strong influence of CMV on the abundance and differentiation pattern of γδ T-cells as well as αβ T-cells in older and younger people. Mechanisms responsible for the phenotypic alterations in the γδ T-cell compartment, associated both with the presence of CMV and with age require further clarification

cDNA Sequence and Fab Crystal Structure of HL4E10, a Hamster IgG Lambda Light Chain Antibody Stimulatory for γδ T Cells

Hamsters are widely used to generate monoclonal antibodies against mouse, rat, and human antigens, but sequence and structural information for hamster immunoglobulins is sparse. To our knowledge, only three hamster IgG sequences have been published, all of which use kappa light chains, and no three-dimensional structure of a hamster antibody has been reported. We generated antibody HL4E10 as a probe to identify novel costimulatory molecules on the surface of γδ T cells which lack the traditional αβ T cell co-receptors CD4, CD8, and the costimulatory molecule CD28. HL4E10 binding to γδ T cell, surface-expressed, Junctional Adhesion Molecule-Like (JAML) protein leads to potent costimulation via activation of MAP kinase pathways and cytokine production, resulting in cell proliferation. The cDNA sequence of HL4E10 is the first example of a hamster lambda light chain and only the second known complete hamster heavy chain sequence. The crystal structure of the HL4E10 Fab at 2.95 Å resolution reveals a rigid combining site with pockets faceted by solvent-exposed tyrosine residues, which are structurally optimized for JAML binding. The characterization of HL4E10 thus comprises a valuable addition to the spartan database of hamster immunoglobulin genes and structures. As the HL4E10 antibody is uniquely costimulatory for γδ T cells, humanized versions thereof may be of clinical relevance in treating γδ T cell dysfunction-associated diseases, such as chronic non-healing wounds and cancer

Mechanisms of activation of innate-like intraepithelial T lymphocytes

Intraepithelial T lymphocytes (T-IEL) contain subsets of innate-like T cells that evoke innate and adaptive immune responses to provide rapid protection at epithelial barrier sites. In the intestine, T-IEL express variable T cell antigen receptors (TCR), with unknown antigen specificities. Intriguingly, they also express multiple inhibitory receptors, many of which are normally found on exhausted or antigen-experienced T cells. This pattern suggests that T-IEL are antigen-experienced, yet it is not clear where, and in what context, T-IEL encounter TCR ligands. We review recent evidence indicating TCR antigens for intestinal innate-like T-IEL are found on thymic or intestinal epithelium, driving agonist selection of T-IEL. We explore the contributions of the TCR and various co-stimulatory and co-inhibitory receptors in activating T-IEL effector functions. The balance between inhibitory and activating signals may be key to keeping these highly cytotoxic, rapidly activated cells in check, and key to harnessing their immune surveillance potential

Chemotactic antiviral cytokines promote infectious apical entry of human adenovirus into polarized epithelial cells

Mucosal epithelia provide strong barriers against pathogens. For instance, the outward facing apical membrane of polarized epithelial cells lacks receptors for agents, such as hepatitis C virus, herpesvirus, reovirus, poliovirus or adenovirus. In addition, macrophages eliminate pathogens from the luminal space. Here we show that human adenovirus type 5 engages an antiviral immune response to enter polarized epithelial cells. Blood-derived macrophages co-cultured apically on polarized epithelial cells facilitate epithelial infection. Infection also occurs in the absence of macrophages, if virus-conditioned macrophage-medium containing the chemotactic cytokine CXCL8 (interleukin-8), or recombinant CXCL8 are present. In polarized cells, CXCL8 activates a Src-family tyrosine kinase via the apical CXCR1 and CXCR2 receptors. This activation process relocates the viral co-receptor ανβ3 integrin to the apical surface, and enables apical binding and infection with adenovirus depending on the primary adenovirus receptor CAR. This paradigm may explain how other mucosal pathogens enter epithelial cells

B(1) and B(2) kinin receptor blockade improves psoriasis-like disease

BACKGROUND AND PURPOSE: Evidence indicates that the entire kallikrein‐kinin system is present in the skin, and it is thought to exert a relevant role in cutaneous diseases, including psoriasis. Thus, the present study was designed to evaluate the relevance of kinin receptors in the development and progression of a psoriasis mice model. EXPERIMENTAL APPROACH: Kinin B(1) and B(2) receptor knockout mice as well as C57BL/6 wild type (WT) mice treated with kinin receptor antagonists (SSR240612C or FR173657) were submitted to the Imiquimod (IMQ)‐induced psoriasis model. KEY RESULTS: Both kinin receptors were upregulated following 6 days of IMQ treatment. Kinin B(1) and B(2) receptor deficiency as well as the use of selective antagonists, show morphological and histological improvement of the psoriasis hallmarks. This protective effect was associated with a decrease in undifferentiated and proliferating keratinocytes, decreased cellularity (neutrophils, macrophages, CD4(+) T lymphocytes), reduced γδ T cells as well as lower accumulation of IL‐17. The lack of B(2) receptors resulted in reduced CD8(+) T cells in the psoriatic skin. Relevantly, blocking kinin receptors reflected the improvement of psoriasis disease in the well‐being behaviour of the mice. CONCLUSIONS AND IMPLICATIONS: The present results have provided clear experimental evidence that kinins exert a critical role in IMQ‐induced psoriasis. Both B(1) and B(2) kinin receptors exacerbate the disease development, influencing keratinocyte proliferation and immunopathology. Therefore, the use of antagonists for one or even both kinin receptors might constitute a new strategy for psoriasis clinical treatment

Development of γδ thymocyte subsets during prenatal and postnatal ontogeny

In this report, we describe 12 subpopulations of porcine γδ thymocytes based on their expression of CD1, CD2, CD4, CD8-isoforms and CD45RC. Our data suggest that γδ thymocytes can be divided into two major families: (a) one large family of CD4(−) γδ thymocytes that could be further subdivided according to the CD2/CD8αα phenotype and (b) a small family of CD4(+) γδ thymocytes bearing CD8αβ and possessing certain unusual features in comparison with other γδ thymocytes. Maturation of γδ thymocytes within the CD4(−) family begins with proliferation of the CD2(+) CD8(−) CD1(+) CD45RC(−) γδ common precursor. This developmental stage is followed by diversification into the CD2(+) CD8αα(+), CD2(+) CD8(−) and CD2(−) CD8(−) subsets. Their further maturation is accompanied by a loss of expression of CD1 and by increased expression of CD45RC. Therefore, individual subsets develop from CD1(+) CD45RC(−) through CD1(−) CD45RC(−) into CD1(−) CD45RC(+) cells. On the other hand, γδ thymocytes within the CD4(+) family bear exclusively CD8αβ, always express CD1, but may coexpress CD45RC. These cells have no counterpart in the periphery. Our observations suggest that all peripheral CD8(+) γδ T cells express CD8αα and that two subsets of these cells differing in major histocompatibility complex II expression, occur. We propose that one subset acquires CD8αα in the thymus while the second acquires CD8αα as a result of stimulation in the periphery