Linking genetic susceptibility and T cell activation in beryllium-induced disease

Methods to Assess Proliferation of Stimulated Human Lymphocytes In Vitro: A Narrative Review

The ability to monitor lymphocyte responses is critical for developing our understanding of the immune response in humans. In the current clinical setting, relying on the metabolic incorporation of [³H] thymidine into cellular DNA via a lymphocyte proliferation test (LPT) is the only method that is routinely performed to determine cell proliferation. However, techniques that measure DNA synthesis with a radioactive material such as [³H] thymidine are intrinsically more sensitive to the different stages of the cell cycle, which could lead to over-analyses and the subsequent inaccurate interpretation of the information provided. With cell proliferation assays, the output should preferably provide a direct and accurate measurement of the number of actively dividing cells, regardless of the stimuli properties or length of exposure. In fact, an ideal technique should have the capacity to measure lymphocyte responses on both a quantitative level, i.e., cumulative magnitude of lymphoproliferative response, and a qualitative level, i.e., phenotypical and functional characterization of stimulated immune cells. There are many LPT alternatives currently available to measure various aspects of cell proliferation. Of the nine techniques discussed, we noted that the majority of these LPT alternatives measure lymphocyte proliferation using flow cytometry. Across some of these alternatives, the covalent labelling of cells with a high fluorescence intensity and low variance with minimal cell toxicity while maximizing the number of detectable cell divisions or magnitude of proliferation was achieved. Herein, we review the performance of these different LPT alternatives and address their compatibility with the [³H] thymidine LPT so as to identify the "best" alternative to the [³H] thymidine LPT.

Innate and Adaptive Immunity in Noninfectious Granulomatous Lung Disease

Sarcoidosis and chronic beryllium disease are noninfectious lung diseases that are characterized by the presence of noncaseating granulomatous inflammation. Chronic beryllium disease is caused by occupational exposure to beryllium containing particles, whereas the etiology of sarcoidosis is not known. Genetic susceptibility for both diseases is associated with particular MHC class II alleles, and CD4⁺ T cells are implicated in their pathogenesis. The innate immune system plays a critical role in the initiation of pathogenic CD4⁺ T cell responses as well as the transition to active lung disease and disease progression. In this review, we highlight recent insights into Ag recognition in chronic beryllium disease and sarcoidosis. In addition, we discuss the current understanding of the dynamic interactions between the innate and adaptive immune systems and their impact on disease pathogenesis.

Occupational Hypersensitivity Pneumonitis in a Japanese Citrus Farmer

Hypersensitivity pneumonitis (HP) sometimes develops in people working in specific environments. We herein report a case of occupation-related HP in a citrus farmer in Japan. A 66-year-old man developed a fever, dyspnea, and general malaise in March after working near a trash dump filled with moldy tangerines. He presented with leukocytosis, bilateral lung opacities on chest radiographs, and intra-alveolar and interstitial lymphocytic inflammation with fibrotic change on a lung biopsy. His symptoms disappeared after admission and recurred on a revisit to the workplace. Fungal culture and a mycobiome analysis using next-generation sequencing suggested an association with exposure to Penicillium digitatum.

Health aspects of exposure to emissions from burning coal of high beryllium content: interactions with the immune system

Beryllium has an impact on the human health of professionally or non-occupationally exposed people. Current evidence suggests that beryllium acts as a hapten with limited antigenic properties and is presented by antigen presenting cells to CD4⁺ T cells, which possess specific antigen receptors. The immunological changes in humoral immunoreactivity were considered biomarkers of beryllium exposure. In the present, due to the development of immunologic knowledge, tests of cellular immunity have promising potential for further research in this field. The historical view of the immune response to beryllium in acute and/or chronic beryllium disease is an example of the development of the interaction between mechanisms of innate and adaptive (specific), humoral and cellular immunity. The authors emphasize the increasing importance of immunological aspects in the studies of health impacts of human exposure to environmental pollutants.

TLR9 and IL-1R1 Promote Mobilization of Pulmonary Dendritic Cells during Beryllium Sensitization

Metal-induced hypersensitivity is driven by dendritic cells (DCs) that migrate from the site of exposure to the lymph nodes, upregulate costimulatory molecules, and initiate metal-specific CD4⁺ T cell responses. Chronic beryllium disease (CBD), a life-threatening metal-induced hypersensitivity, is driven by beryllium-specific CD4⁺ Th1 cells that expand in the lung-draining lymph nodes (LDLNs) after beryllium exposure (sensitization phase) and are recruited back to the lung, where they orchestrate granulomatous lung disease (elicitation phase). To understand more about how beryllium exposures impact DC function during sensitization, we examined the early events in the lung and LDLNs after pulmonary exposure to different physiochemical forms of beryllium. Exposure to soluble or crystalline forms of beryllium induced alveolar macrophage death/release of IL-1α and DNA, enhanced migration of CD80^hi DCs to the LDLNs, and sensitized HLA-DP2 transgenic mice after single low-dose exposures, whereas exposures to insoluble particulate forms beryllium did not. IL-1α and DNA released by alveolar macrophages upregulated CD80 on immature BMDC via IL-1R1 and TLR9, respectively. Intrapulmonary exposure of mice to IL-1R and TLR9 agonists without beryllium was sufficient to drive accumulation of CD80^hi DCs in the LDLNs, whereas blocking both pathways prevented accumulation of CD80^hi DCs in the LDLNs of beryllium-exposed mice. Thus, in contrast to particulate forms of beryllium, which are poor sensitizers, soluble or crystalline forms of beryllium promote death of alveolar macrophages and their release of IL-1α and DNA, which act as damage-associated molecular pattern molecules to enhance DC function during beryllium sensitization.

Impaired function of CTLA-4 in the lungs of patients with chronic beryllium disease contributes to persistent inflammation

Chronic beryllium disease (CBD) is an occupational lung disorder characterized by granulomatous inflammation and the accumulation of beryllium-responsive CD4(+) T cells in the lung. These differentiated effector memory T cells secrete IL-2, IFN-γ, and TNF-α upon in vitro activation. Beryllium-responsive CD4(+) T cells in the lung are CD28 independent and have increased expression of the coinhibitory receptor, programmed death 1, resulting in Ag-specific T cells that proliferate poorly yet retain the ability to express Th1-type cytokines. To further investigate the role of coinhibitory receptors in the beryllium-induced immune response, we examined the expression of CTLA-4 in blood and bronchoalveolar lavage cells from subjects with CBD. CTLA-4 expression was elevated on CD4(+) T cells from the lungs of study subjects compared with blood. Furthermore, CTLA-4 expression was greatest in the beryllium-responsive subset of CD4(+) T cells that retained the ability to proliferate and express IL-2. Functional assays show that the induction of CTLA-4 signaling in blood cells inhibited beryllium-induced T cell proliferation while having no effect on the proliferative capacity of beryllium-responsive CD4(+) T cells in the lung. Collectively, our findings suggest a dysfunctional CTLA-4 pathway in the lung and its potential contribution to the persistent inflammatory response that characterizes CBD.

T-cell receptor (TCR) interaction with peptides that mimic nickel offers insight into nickel contact allergy

T cell-mediated allergy to Ni(++) is one of the most common forms of allergic contact dermatitis, but how the T-cell receptor (TCR) recognizes Ni(++) is unknown. We studied a TCR from an allergic patient that recognizes Ni(++) bound to the MHCII molecule DR52c containing an unknown self-peptide. We identified mimotope peptides that can replace both the self-peptide and Ni(++) in this ligand. They share a p7 lysine whose εNH(2) group is surface-exposed when bound to DR52c. Whereas the TCR uses germ-line complementary-determining region (CDR)1/2 amino acids to dock in the conventional diagonal mode on the mimotope-DR52c complex, the interface is dominated by the TCR Vβ CDR3 interaction with the p7 lysine. Mutations in the TCR CDR loops have similar effects on the T-cell response to either the mimotope or Ni(++) ligand. We suggest that the mimotope p7 lysine mimics Ni(++) in the natural TCR ligand and that MHCII β-chain flexibility in the area around the peptide p7 position forms a common site for cation binding in metal allergies.

HLA associations and Löfgren's syndrome

Patients with sarcoidosis can be subgrouped according to organ engagement and clinical manifestations. One such subgroup is Löfgren's syndrome (LS), constituting a distinct group of sarcoidosis patients with typical clinical manifestations, separate genetic associations and an immune response that seems to differ from that of non-LS patients. In particular, LS patients have strong associations with HLA-DRB1 alleles, and the well-known association with HLA-DRB1*03 is particularly striking. This particular HLA-DRB1 allele is also a very strong marker within that particular group of patients for a prognostically favorable disease course. This article will mainly discuss genetic associations with LS, and the possible implications of such associations.

Mutagenesis of beryllium-specific TCRs suggests an unusual binding topology for antigen recognition

Unconventional Ags, such as metals, stimulate T cells in a very specific manner. To delineate the binding landscape for metal-specific T cell recognition, alanine screens were performed on a set of Be-specific TCRs derived from the lung of a chronic beryllium disease patient. These TCRs are HLA-DP2-restricted and express nearly identical TCR Vβ5.1 chains coupled with different TCR α-chains. Site-specific mutagenesis of all amino acids comprising the CDRs of the TCRA and TCRB genes showed a dominant role for Vβ5.1 residues in Be recognition, with little contribution from the TCR α-chain. Solvent-exposed residues along the α-helices of the HLA-DP2 α- and β-chains were also mutated to alanine. Two β-chain residues, located near the proposed Be binding site of HLA-DP2, played a dominant role in T cell recognition with no contribution from the HLA-DP2 α-chain. These findings suggest that Be-specific T cells recognize Ag using an unconventional binding topology, with the majority of interactions contributed by TCR Vβ5.1 residues and the HLA-DP2 β1-chain. Thus, unusual docking topologies are not exclusively used by autoreactive T cells, but also for the recognition of unconventional metal Ags, such as Be.

Nanotoxicology--a pathologist's perspective

Advances in chemistry and engineering have created a new technology, nanotechnology, involving the tiniest known manufactured products. These products have a rapidly increasing market share and appear poised to revolutionize engineering, cosmetics, and medicine. Unfortunately, nanotoxicology, the study of nanoparticulate health effects, lags behind advances in nanotechnology. Over the past decade, existing literature on ultrafine particles and respirable durable fibers has been supplemented by studies of first-generation nanotechnology products. These studies suggest that nanosizing increases the toxicity of many particulates. First, as size decreases, surface area increases, thereby speeding up dissolution of soluble particulates and exposing more of the reactive surface of durable but reactive particulates. Second, nanosizing facilitates movement of particulates across cellular and intracellular barriers. Third, nanosizing allows particulates to interact with, and sometimes even hybridize with, subcellular structures, including in some cases microtubules and DNA. Finally, nanosizing of some particulates, increases pathologic and physiologic responses, including inflammation, fibrosis, allergic responses, genotoxicity, and carcinogenicity, and may alter cardiovascular and lymphatic function. Knowing how the size and physiochemical properties of nanoparticulates affect bioactivity is important in assuring that the exciting new products of nanotechnology are used safely. This review provides an introduction to the pathology and toxicology of nanoparticulates.