SARS-CoV-2-specific T cells associate with inflammation and reduced lung function in pulmonary post-acute sequalae of SARS-CoV-2

As of January 2022, at least 60 million individuals are estimated to develop post-acute sequelae of SARS-CoV-2 (PASC) after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While elevated levels of SARS-CoV-2-specific T cells have been observed in non-specific PASC, little is known about their impact on pulmonary function which is compromised in the majority of these individuals. This study compares frequencies of SARS-CoV-2-specific T cells and inflammatory markers with lung function in participants with pulmonary PASC and resolved COVID-19 (RC). Compared to RC, participants with respiratory PASC had between 6- and 105-fold higher frequencies of IFN-γ- and TNF-α-producing SARS-CoV-2-specific CD4+ and CD8+ T cells in peripheral blood, and elevated levels of plasma CRP and IL-6. Importantly, in PASC participants the frequency of TNF-α-producing SARS-CoV-2-specific CD4+ and CD8+ T cells, which exhibited the highest levels of Ki67 indicating they were activity dividing, correlated positively with plasma IL-6 and negatively with measures of lung function, including forced expiratory volume in one second (FEV1), while increased frequencies of IFN-γ-producing SARS-CoV-2-specific T cells associated with prolonged dyspnea. Statistical analyses stratified by age, number of comorbidities and hospitalization status demonstrated that none of these factors affect differences in the frequency of SARS-CoV-2 T cells and plasma IL-6 levels measured between PASC and RC cohorts. Taken together, these findings demonstrate elevated frequencies of SARS-CoV-2-specific T cells in individuals with pulmonary PASC are associated with increased systemic inflammation and decreased lung function, suggesting that SARS-CoV-2-specific T cells contribute to lingering pulmonary symptoms. These findings also provide mechanistic insight on the pathophysiology of PASC that can inform development of potential treatments to reduce symptom burden.

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.

CD4+ T cells in the lungs of acute sarcoidosis patients recognize an Aspergillus nidulans epitope

Löfgren’s syndrome (LS) is an acute form of sarcoidosis characterized by a genetic association with HLA-DRB1*03 (HLA-DR3) and an accumulation of CD4⁺ T cells of unknown specificity in the bronchoalveolar lavage (BAL). Here, we screened related LS-specific TCRs for antigen specificity and identified a peptide derived from NAD-dependent histone deacetylase hst4 (NDPD) of Aspergillus nidulans that stimulated these CD4⁺ T cells in an HLA-DR3–restricted manner. Using ELISPOT analysis, a greater number of IFN-γ– and IL-2–secreting T cells in the BAL of DR3⁺ LS subjects compared with DR3⁺ control subjects was observed in response to the NDPD peptide. Finally, increased IgG antibody responses to A. nidulans NDPD were detected in the serum of DR3⁺ LS subjects. Thus, our findings identify a ligand for CD4⁺ T cells derived from the lungs of LS patients and suggest a role of A. nidulans in the etiology of LS.

Beryllium-specific CD4+ T cells induced by chemokine neoantigens perpetuate inflammation

Discovering dominant epitopes for T cells, particularly CD4+ T cells, in human immune-mediated diseases remains a significant challenge. Here, we used bronchoalveolar lavage (BAL) cells from HLA-DP2-expressing patients with chronic beryllium disease (CBD), a debilitating granulomatous lung disorder characterized by accumulations of beryllium-specific (Be-specific) CD4+ T cells in the lung. We discovered lung-resident CD4+ T cells that expressed a disease-specific public CDR3β T cell receptor motif and were specific to Be-modified self-peptides derived from C-C motif ligand 4 (CCL4) and CCL3. HLA-DP2-CCL/Be tetramer staining confirmed that these chemokine-derived peptides represented major antigenic targets in CBD. Furthermore, Be induced CCL3 and CCL4 secretion in the lungs of mice and humans. In a murine model of CBD, the addition of LPS to Be oxide exposure enhanced CCL4 and CCL3 secretion in the lung and significantly increased the number and percentage of CD4+ T cells specific for the HLA-DP2-CCL/Be epitope. Thus, we demonstrate a direct link between Be-induced innate production of chemokines and the development of a robust adaptive immune response to those same chemokines presented as Be-modified self-peptides, creating a cycle of innate and adaptive immune activation.

Shared αβ TCR Usage in Lungs of Sarcoidosis Patients with Löfgren's Syndrome

Sarcoidosis is a granulomatous disease that primarily affects the lungs and is characterized by an accumulation of CD4⁺ T cells in the bronchoalveolar lavage (BAL). Previous work has indicated that HLA-DRB1*03:01⁺ (DR3⁺) patients diagnosed with the acute form of the disease, Löfgren's syndrome (LS), have an accumulation of CD4⁺ T cells bearing TCRs using TRAV12-1 (formerly AV2S3). However, the importance of these α-chains in disease pathogenesis and the paired TCRβ-chain remains unknown. This study aimed to identify expanded αβTCR pairs expressed on CD4⁺ T cells derived from the BAL of DR3⁺ LS patients. Using a deep-sequencing approach, we determined TCRα- and TCRβ-chain usage, as well as αβTCR pairs expressed on BAL CD4⁺ T cells from LS patients. TRAV12-1 and TRBV2 (formerly BV22) were the most expanded V region gene segments in DR3⁺ LS patients relative to control subjects, and TRAV12-1 and TRBV2 CDR3 motifs were shared among multiple DR3⁺ LS patients. When assessing αβTCR pairing, TRAV12-1 preferentially paired with TRBV2, and these TRAV12-1/TRBV2 TCRs displayed CDR3 homology. These findings suggest that public CD4⁺ TCR repertoires exist among LS patients and that these T cells are recognizing the putative sarcoidosis-associated Ag(s) in the context of DR3.

CD4+ T cell receptor repertoire in sarcoidosis patients

Sarcoidosis is a multisystem disorder that most commonly affects the lungs and involves granuloma formation with the accumulation of CD4+ T cells at sites of disease. Considerable evidence indicates that CD4+ T cells are involved in the initiation and perpetuation of sarcoidosis. Particular T cell clones within the bronchoalveolar lavage (BAL) are preferentially expanded in patients with sarcoidosis, and these oligoclonal T cell populations accumulate within the lung and disappear with disease resolution. A link between the expansions of CD4+T cells expressing the T cell receptor (TCR) α-chain variable (V) region Vα2.3 and the presence of the HLA-DRB1*0301 (DR3) allele in sarcoidosis patients has been seen. We hypothesize that sarcoidosis-specific CD4+ T cells accumulate and expand in the lungs of sarcoidosis patients in response to a specific antigen. To determine whether these expanded CD4+T cell clones play a pathogenic role in disease progression, as well as to address their antigen specificity, we analyzed the TCR repertoire of CD4+ T cells isolated from the BAL of sarcoidosis patients utilizing iRepertoire, emulsion PCR, and single cell PCR analyses. We identified TCR Vα2.3/Jα42 CDR3 motifs that were found exclusively in HLA-DR3+ sarcoidosis patients (the motifs were not found in DR3− or DR3+ healthy control patients), suggesting a public TCR repertoire in this subset of patients. Importantly, these α-chains were paired with differing β-chains, suggesting a critical role of the α-chains in recognizing the HLA-DR3-peptide complex.

Beryllium-Induced Hypersensitivity: Genetic Susceptibility and Neoantigen Generation

Chronic beryllium (Be) disease is a granulomatous lung disorder that results from Be exposure in a genetically susceptible host. The disease is characterized by the accumulation of Be-responsive CD4(+) T cells in the lung, and genetic susceptibility is primarily linked to HLA-DPB1 alleles possessing a glutamic acid at position 69 of the β-chain. Recent structural analysis of a Be-specific TCR interacting with a Be-loaded HLA-DP2-peptide complex revealed that Be is coordinated by amino acid residues derived from the HLA-DP2 β-chain and peptide and showed that the TCR does not directly interact with the Be(2+) cation. Rather, the TCR recognizes a modified HLA-DP2-peptide complex with charge and conformational changes. Collectively, these findings provide a structural basis for the development of this occupational lung disease through the ability of Be to induce posttranslational modifications in preexisting HLA-DP2-peptide complexes, resulting in the creation of neoantigens.

Identifying T cell antigens in sarcoidosis

Sarcoidosis is a multisystem disorder which most commonly affects the lungs and involves the accumulation of CD4+ T cells at the sites of disease. The etiology of the disease is unknown, and the lack of a known antigen has hindered the study of disease pathogenesis. However, there is considerable evidence that CD4+ T cells are involved in the initiation and perpetuation of sarcoidosis. Previous work by our lab and others has demonstrated that particular T cell clones within the bronchoalveolar lavage (BAL) have been preferentially expanded in patients with sarcoidosis. These oligoclonal T cell populations accumulate within the lung and disappear with disease resolution. Furthermore, correlations have been observed between the expansions of CD4+T cells expressing the T cell receptor (TCR) α-chain variable (V) region Vα2.3 and the presence of the HLA-DRB1*0301 (DR3) allele in certain patient populations. Preliminary data suggest that cells within the BAL expressing TCRs utilizing Vα2.3, Vβ5.1, and Vβ5.3 are preferentially expanded before and after ex-vivo stimulation with IL-2. We hypothesize that sarcoidosis-specific CD4+ T cells accumulate and expand in the lungs of sarcoidosis patients in response to a specific antigen. To determine whether these expanded CD4+T cell clones play a pathogenic role in disease progression, as well as to address their antigen specificity, the TCRs of these clones have been characterized, and a combinatorial peptide library has been screened to identify candidate antigens that stimulate these clones. These unbiased data will provide clues to the disease-initiating antigens that drive sarcoidosis in a subset of patients and will lead to an extension of our findings to a larger disease cohort.

Metal-specific CD4+ T-cell responses induced by beryllium exposure in HLA-DP2 transgenic mice

Chronic beryllium disease (CBD) is a granulomatous lung disorder that is associated with the accumulation of beryllium (Be)-specific CD4(+) T cells into the lung. Genetic susceptibility is linked to HLA-DPB1 alleles that possess a glutamic acid at position 69 (βGlu69), and HLA-DPB1*02:01 is the most prevalent βGlu69-containing allele. Using HLA-DP2 transgenic (Tg) mice, we developed a model of CBD that replicates the major features of the human disease. Here we characterized the T-cell receptor (TCR) repertoire of Be-responsive CD4(+) T cells derived from the lungs of Be oxide-exposed HLA-DP2 Tg mice. The majority of Be-specific T-cell hybridomas expressed TCR Vβ6, and a subset of these hybridomas expressed identical or nearly identical β-chains that were paired with different α-chains. We delineated mimotopes that bind to HLA-DP2 and form a complex recognized by Be-specific CD4(+) T cells in the absence of Be. These Be-independent peptides possess an arginine at p5 and a tryptophan at p7 that surround the Be-binding site within the HLA-DP2 acidic pocket and likely induce charge and conformational changes that mimic those induced by the Be(2+) cation. Collectively, these data highlight the interplay between peptides and Be in the generation of an adaptive immune response in metal-induced hypersensitivity.

Identification of multiple public TCR repertoires in chronic beryllium disease

Chronic beryllium disease (CBD) is a granulomatous lung disease characterized by the accumulation of beryllium (Be)-specific CD4(+) T cells in bronchoalveolar lavage. These expanded CD4(+) T cells are composed of oligoclonal T cell subsets, suggesting their recruitment to the lung in response to conventional Ag. In the current study, we noted that all bronchoalveolar lavage-derived T cell lines from HLA-DP2-expressing CBD patients contained an expansion of Be-responsive Vβ5.1(+) CD4(+) T cells. Using Be-loaded HLA-DP2-peptide tetramers, the majority of tetramer-binding T cells also expressed Vβ5.1 with a highly conserved CDR3β motif. Interestingly, Be-specific, Vβ5.1-expressing CD4(+) T cells displayed differential HLA-DP2-peptide tetramer staining intensity, and sequence analysis of the distinct tetramer-binding subsets showed that the two populations differed by a single conserved amino acid in the CDR3β motif. TCR Vα-chain analysis of purified Vβ5.1(+) CD4(+) T cells based on differential tetramer-binding intensity showed differing TCR Vα-chain pairing requirements, with the high-affinity population having promiscuous Vα-chain pairing and the low-affinity subset requiring restricted Vα-chain usage. Importantly, disease severity, as measured by loss of lung function, was inversely correlated with the frequency of tetramer-binding CD4(+) T cells in the lung. Our findings suggest the presence of a dominant Be-specific, Vβ5.1-expressing public T cell repertoire in the lungs of HLA-DP2-expressing CBD patients using promiscuous Vα-chain pairing to recognize an identical HLA-DP2-peptide/Be complex. Importantly, the inverse relationship between expansion of CD4(+) T cells expressing these public TCRs and disease severity suggests a pathogenic role for these T cells in CBD.

Identification of beryllium-dependent peptides recognized by CD4+ T cells in chronic beryllium disease

Identification of peptides that form complexes with beryllium and class II HLA molecules and are recognized by CD4⁺ T cells from patients with chronic beryllium disease.

Chronic beryllium disease (CBD) is a granulomatous disorder characterized by an influx of beryllium (Be)-specific CD4⁺ T cells into the lung. The vast majority of these T cells recognize Be in an HLA-DP–restricted manner, and peptide is required for T cell recognition. However, the peptides that stimulate Be-specific T cells are unknown. Using positional scanning libraries and fibroblasts expressing HLA-DP2, the most prevalent HLA-DP molecule linked to disease, we identified mimotopes and endogenous self-peptides that bind to MHCII and Be, forming a complex recognized by pathogenic CD4⁺ T cells in CBD. These peptides possess aspartic and glutamic acid residues at p4 and p7, respectively, that surround the putative Be-binding site and cooperate with HLA-DP2 in Be coordination. Endogenous plexin A peptides and proteins, which share the core motif and are expressed in lung, also stimulate these TCRs. Be-loaded HLA-DP2–mimotope and HLA-DP2–plexin A4 tetramers detected high frequencies of CD4⁺ T cells specific for these ligands in all HLA-DP2⁺ CBD patients tested. Thus, our findings identify the first ligand for a CD4⁺ T cell involved in metal-induced hypersensitivity and suggest a unique role of these peptides in metal ion coordination and the generation of a common antigen specificity in CBD.

Highly conserved CDR3 region in circulating CD4(+)Vβ5(+) T cells may be associated with cytotoxic activity in Chagas disease

Human infection with Trypanosoma cruzi leads to Chagas disease, which presents as several different clinical conditions ranging from an asymptomatic form to a severe dilated cardiomyopathy. Several studies have demonstrated that T cells play a critical role in the development of cardiac pathology, as well as in immunoregulation during chronic disease. However, the mechanisms that drive protective or pathogenic T cell response are not known. We have shown that CD4(+) T cells from chagasic patients preferentially express T cell receptor (TCR) β-chain variable region (Vβ) 5. The aim of this work was to determine whether T cells expressing this particular Vβ region displayed variable or restricted CDR3 sequences, as an indicator of the nature of the stimulus leading to the activation of these T cells in vivo. Additionally, we aimed to evaluate phenotypic characteristics of these cells that might be associated with pathology. CDR3 junctional region sequencing of Vβ5·1 expressing CD4(+) T cells revealed the occurrence of a highly homologous CDR3 region with conserved TCR Jβ region usage among patients with cardiac, but not indeterminate, Chagas disease. Moreover, correlation analysis indicated that the frequency of CD4(+)Vβ5·1(+) cells is associated with granzyme A expression, suggesting that these cells might display cytotoxic function. Together these results provide new insight into T cell recognition of antigens involved in Chagas disease and suggest that these cells may be implicated in the pathogenesis of chagasic cardiomyopathy.

Beryllium-specific CD4+ T cells in blood as a biomarker of disease progression

BACKGROUND

CD4(+) T cells are responsible for the progressive lung damage seen in patients with chronic beryllium disease (CBD), a granulomatous lung disorder in which antigen-specific, T(H)1-type, cytokine-secreting T cells have been characterized. Compared with those seen in beryllium (Be)-sensitized subjects, increased numbers of Be-responsive T cells are present in the blood of patients with CBD.

OBJECTIVE

The aim of this study was to determine whether the number of Be-specific T cells in blood predicted the development of CBD in a cohort of Be-exposed subjects.

METHODS

Using IFN-γ ELISpot and proliferation-based assays, we determined the frequency and proliferative capacity of Be-responsive T cells in blood.

RESULTS

Compared with the Be lymphocyte proliferation test, which detected an abnormal Be-induced proliferative response in 11 (4.2%) of 260 workers from a Be-machining facility, the IFN-γ ELISpot detected a sensitization rate of 10% (χ(2) = 55.7, P < .0001). A significant positive correlation was also noted between the number of Be-responsive CD4(+) T cells in the blood and lung tissue of patients with CBD. Importantly, the transition from Be sensitization to CBD was associated with an increased number of antigen-specific T cells in blood.

CONCLUSION

These findings have important implications for Be-induced disease and potentially other immune-mediated disorders, suggesting that the frequency of antigen-specific T cells in blood can serve as a noninvasive biomarker to predict disease development and severity of the Be-specific CD4(+) T-cell alveolitis.

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.

Defective leukocyte GM-CSF receptor (CD116) expression and function in inflammatory bowel disease

BACKGROUND & AIMS

Inflammatory bowel disease (IBD) refers to 2 chronic inflammatory diseases of the intestine, ie, ulcerative colitis and Crohn's disease. IBD results from environmental factors (eg, bacterial antigens) triggering a dysregulated immune response in genetically predisposed hosts. Although the basis of IBD is incompletely understood, a number of recent studies have implicated defective innate immune responses in the pathogenesis of IBD. In this regard, there is much interest in therapies that activate innate immunity (eg, recombinant granulocyte-macrophage colony-stimulating factor).

METHODS

In this study, we screened expression and function of circulating leukocyte granulocyte-macrophage colony-stimulating factor receptor (CD116) messenger RNA and surface protein in 52 IBD patients and 52 healthy controls.

RESULTS

Our results show that both granulocyte and monocyte CD116 levels, but not CD114 or interleukin-3Rα, were significantly decreased in IBD compared to control (P<.001) and disease controls (irritable bowel syndrome; P<.001; rheumatoid arthritis; P<.025). IBD-associated CD116 repression was more prominent in patients with ulcerative colitis compared to Crohn's disease (P<.05), was independent of disease activity (P>.05), and was not influenced by current medications (P>.05). Receiver operating characteristic curve analysis revealed that leukocyte CD116 expression is a sensitive (85%) and specific (92%) biomarker for IBD. Moreover, granulocyte CD116-mediated function (phosphorylation of signal transducers and activators of transcription 3) paralleled decreased expression of CD116 in IBD granulocytes compared to control (P<.001).

CONCLUSIONS

These studies identify defective expression and function of CD116 as a distinguishing feature of IBD and implicate an associated defect in innate immune responses toward granulocyte-macrophage colony-stimulating factor.

Deficient and dysfunctional regulatory T cells in the lungs of chronic beryllium disease subjects

RATIONALE

Chronic beryllium disease (CBD) is a CD4(+) T cell-mediated disorder characterized by persistent lung inflammation. Naturally occurring regulatory T (T(reg)) cells modulate adaptive immune responses. The role of this T-cell subset in beryllium-induced lung disease is unknown.

OBJECTIVES

The aim of this study was to determine whether dysfunctional T(reg) cells in the lung contribute to the "unchecked" inflammatory response that characterizes CBD.

METHODS

Using blood and bronchoalveolar lavage (BAL) cells from normal control subjects and individuals with beryllium-induced disease, we determined the frequency and function of naturally occurring T(reg) cells.

MEASUREMENTS AND MAIN RESULTS

A significantly decreased percentage and expression of FoxP3 in BAL CD4(+) T cells from CBD patients compared with beryllium-sensitized subjects was seen, and the percentage of FoxP3-expressing CD4(+) T(reg) cells in BAL inversely correlated with disease severity. In contrast to blood T(reg) cells derived from beryllium-sensitized subjects and patients with CBD that completely suppressed blood responder T-cell proliferation, BAL FoxP3-expressing T(reg) cells from patients with CBD are unable to suppress anti-CD3-mediated BAL T-cell proliferation. Mixing studies showed that blood T(reg) cells are capable of suppressing autologous BAL responder T cells. Conversely, BAL CD4(+) T(reg) cells are incapable of suppressing blood T cells, confirming that the failure of BAL T(reg) cells to suppress T-cell proliferation is caused by a dysfunctional T(reg) cell subset and not by resistance of BAL effector T cells to suppression.

CONCLUSIONS

These findings suggest that the deficient and dysfunctional T(reg) cells in the lung of patients with CBD contribute to the persistent inflammatory response in this disease.

Genetic susceptibility to polyI:C-induced IFNalpha/beta-dependent accelerated disease in lupus-prone mice

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown etiology. Associations between viral infections and the onset of SLE have been suggested, and recent studies have provided evidence that type I interferons (IFNalpha/beta) might play a role in the SLE disease process. Viruses and interferons have also been implicated in mouse models of SLE. We generated a model of accelerated proteinuria, in which lupus-prone mice were injected repeatedly with polyinosinic:polycytidylic acid (polyI:C), mimicking exposure to virus-derived double stranded RNA (dsRNA), leading to the production of IFNalpha/beta. PolyI:C-treated (B6.Nba2 x NZW)F1 and (B6 x NZW)F1 hybrid mice developed significantly increased levels of anti-dsDNA autoantibodies, characteristic of lupus. Most significantly, polyI:C-treated (B6.Nba2 x NZW)F1 mice, but not (B6 x NZW)F1 or parental strains, developed lupus-like nephritis in an accelerated fashion, which was dependent on IFNalpha/beta and associated with elevated deposition of total IgG, IgG2a and complement factor C3 in the glomerular capillary walls. These data suggest that reagents, which increase the levels of endogenous IFNalpha/beta (directly or indirectly), can accelerate the course of lupus-like nephritis, the development of which is dependent on the presence of both NZW- and Nba2-encoded genes.

Beryllium Presentation to CD4+ T Cells Is Dependent on a Single Amino Acid Residue of the MHC Class II β-Chain

Chronic beryllium disease (CBD) is characterized by a CD4+ T cell alveolitis and granulomatous inflammation in the lung. Genetic susceptibility to this disease has been linked with HLA-DP alleles, particularly those possessing a glutamic acid at position 69 (Glu69) of the beta-chain. However, 15% of CBD patients do not possess a Glu69-containing HLA-DP allele, suggesting that other MHC class II alleles may be involved in disease susceptibility. In CBD patients without a Glu69-containing HLA-DP allele, an increased frequency of HLA-DR13 alleles has been described, and these alleles possess a glutamic acid at position 71 of the beta-chain (which corresponds to position 69 of HLA-DP). Thus, we hypothesized that beryllium presentation to CD4+ T cells was dependent on a glutamic acid residue at the identical position of both HLA-DP and -DR. The results show that HLA-DP Glu69- and HLA-DR Glu71-expressing molecules are capable of inducing beryllium-specific proliferation and IFN-gamma expression by lung CD4+ T cells. Using fibroblasts expressing mutated HLA-DP2 and -DR13 molecules, beryllium recognition was dependent on the glutamic acid at position 69 of HLA-DP and 71 of HLA-DR, suggesting a critical role for this amino acid in beryllium presentation to Ag-specific CD4+ T cells. Thus, these results demonstrate that a single amino acid residue of the MHC class II beta-chain dictates beryllium presentation and potentially, disease susceptibility.

Class II major histocompatibility complex-peptide tetramer staining in relation to functional avidity and T cell receptor diversity in the mouse CD4(+) T cell response to a rheumatoid arthritis-associated antigen

OBJECTIVE

Although studies have suggested that human cartilage (HC) gp-39 may be an antigen recognized by autoreactive CD4(+) T cells in rheumatoid arthritis, we previously failed to identify specific CD4(+) T cells in patients' synovial fluid or blood using a class II major histocompatibility complex-peptide tetramer composed of the immunodominant HC gp-39(263-275) epitope covalently linked to DR4. We undertook this study to better understand the parameters for specific binding of this tetramer.

METHODS

DR4-transgenic mice were immunized with the HC gp-39 peptide, and a set of peptide-responsive hybridomas was derived. Hybridomas were stained with the DR4-gp-39 tetramer and cultured with increasing amounts of peptide in the presence of DR4-expressing antigen-presenting cells to determine functional avidity.

RESULTS

Great variability was apparent in the ability of the tetramer to stain the hybridomas, and there was a strong correlation between the intensity of tetramer staining and functional avidity. Importantly, nearly 30% of the hybridomas did not stain with tetramer, and these cells exhibited relatively low functional avidity. Although the addition of an anti-T cell receptor (anti-TCR) monoclonal antibody during the staining procedure enhanced binding of the tetramer to a number of the hybridomas, a significant percentage remained unstainable. Analysis of TCR expression showed that >90% of the hybridomas expressed the same TCR beta-chain variable region (V(beta)10), and sequencing of the TCR junctional regions showed diversity in the third complementarity-determining region.

CONCLUSION

These results suggest that immune responses dominated by relatively low-affinity TCR interactions, such as those that may occur in autoimmune disease, will be difficult to detect using standard tetramer techniques.

Oligoclonal CD4+ T cells in the lungs of patients with severe emphysema

RATIONALE

Within the lungs of patients with severe emphysema, inflammation continues despite smoking cessation. Foci of T lymphocytes in the small airways of patients with emphysema have been associated with disease severity. Whether these T cells play an important role in this continued inflammatory response is unknown.

OBJECTIVE

The aim of this study was to determine if T cells recruited to the lungs of subjects with severe emphysema contain oligoclonal T-cell populations, suggesting their accumulation in response to antigenic stimuli.

METHODS

Lung T-cell receptor (TCR) Vbeta repertoire from eight patients with severe emphysema and six control subjects was evaluated at the time of tissue procurement (ex vivo) and after 2 weeks of culture with interleukin 2 (in vitro). Junctional region nucleotide sequencing of expanded TCR-Vbeta subsets was performed.

RESULTS

No significantly expanded TCR-Vbeta subsets were identified in ex vivo samples. However, T cells grew from all emphysema (n = 8) but from only one of the control lung samples (n = 6) when exposed to interleukin 2 (p = 0.0013). Within the cultured cells, seven major CD4-expressing TCR-Vbeta subset expansions were identified from five of the patients with emphysema. These expansions were composed of oligoclonal populations of T cells that had already been expanded in vivo.

CONCLUSION

Severe emphysema is associated with inflammation involving T lymphocytes that are composed of oligoclonal CD4+ T cells. These T cells are accumulating in the lung secondary to conventional antigenic stimulation and are likely involved in the persistent pulmonary inflammation characteristic of severe emphysema.

Antigen-specific T cells in rheumatoid arthritis

There is considerable evidence of a key role for CD4+ T cells in the pathogenesis of rheumatoid arthritis. Several attractive candidate antigens, mostly joint-specific, have been studied, but information regarding T cell responses to these antigens in patients is limited and occasionally contradictory. Novel reagents (such as major histocompatibility complex and peptide tetramers) and sensitive techniques (such as intracellular cytokine staining) will aid in future studies to identify antigen-specific T cells. In addition, a new animal model of inflammatory arthritis has recently provided new perspective to the study of rheumatoid arthritis by drawing attention to systemic self-antigens as targets of autoimmunity and anti-self antibodies as markers of T cell activity and effectors of disease.

Azathioprine associated T-cell mutations in insulin-dependent diabetes mellitus

Somatic mutations arise regularly in human T lymphocytes. As these events occur at increased frequencies in several autoimmune disorders, presumably because of increased T-cell proliferation, we investigated if this is also true for insulin-dependent diabetes mellitus (IDDM). Mutations of the hypoxanthine guanine phosphoribosyltransferase (hprt) gene measured by 6-thioguanine (TG) selection were studied in 28 patients (60 determinations) enrolled in a prospective double-blinded placebo-controlled study of azathioprine immunosuppression: 17 patients (34 determinations) were receiving azathioprine and 11 (26 determinations) placebo. Mean hprt T-cell mutant frequencies (MFs) were elevated in both patient groups, but only in the azathioprine group were elevations large and statistically correlated with the duration of the therapy. These results suggest that the organ-specific antigenic stimulus of the T-cell proliferation in IDDM does increase mutant cells in the peripheral blood, but this increase is relatively small. However, azathioprine, which is converted to 6-mercaptopurine in vivo, selects and amplifies the hprt mutants that do arise. Clinical azathioprine resistance may be explained by hprt mutations arising in T cells relevant to the underlying autoimmune process. Monitoring for these mutations should allow more effective use of this immunosuppressive agent.

Functional subsets within clonally expanded CD8(+) memory T cells in elderly humans

With advancing age, healthy humans frequently demonstrate large clonal expansions of CD8(+) T cells in the peripheral blood, which persist for long periods of time and appear to be maintained as a population of memory cells. We studied nine large T cell clones in five elderly individuals. We noted that in most cases the expanded clones were dominated by cells that did not express CD28, a pivotal molecule in T cell activation, and these clones proliferated poorly in culture. However, nearly all of the clonal expansions had CD28(+) fractions and some of these cells appeared to lose CD28 gene expression with stimulation in culture. CD28(+) cells demonstrated greater proliferation in both bulk and limiting dilution cultures compared to CD28(-) cells bearing the same TCR, whereas CD28(-) cells showed increased perforin expression. Together, these data suggest that loss of CD28 expression marks functional differentiation to cytotoxic memory cells within these clonal expansions and likely within CD8(+) memory populations in general.

Use of soluble peptide-DR4 tetramers to detect synovial T cells specific for cartilage antigens in patients with rheumatoid arthritis

Considerable evidence indicates that CD4(+) T cells are important in the pathogenesis of rheumatoid arthritis (RA), but the antigens recognized by these T cells in the joints of patients remain unclear. Previous studies have suggested that type II collagen (CII) and human cartilage gp39 (HCgp39) are among the most likely synovial antigens to be involved in T cell stimulation in RA. Furthermore, experiments have defined dominant peptide determinants of these antigens when presented by HLA-DR4, the most important RA-associated HLA type. We used fluorescent, soluble peptide-DR4 complexes (tetramers) to detect synovial CD4(+) T cells reactive with CII and HCgp39 in DR4(+) patients. The CII-DR4 complex bound in a specific manner to CII peptide-reactive T cell hybridomas, but did not stain a detectable fraction of synovial CD4(+) cells. A background percentage of positive cells (<0.2%) was not greater in DR4 (DRB1*0401) patients compared with those without this disease-associated allele. Similar results were obtained with the gp39-DR4 complex for nearly all RA patients. In a small subset of DR4(+) patients, however, the percentage of synovial CD4(+) cells binding this complex was above background and could not be attributed to nonspecific binding. These studies demonstrate the potential for peptide-MHC class II tetramers to be used to track antigen-specific T cells in human autoimmune diseases. Together, the results also suggest that the major oligoclonal CD4(+) T cell expansions present in RA joints are not specific for the dominant CII and HCgp39 determinants.

Identification of Pathogenic T Cells in Patients with Beryllium-Induced Lung Disease

Chronic beryllium disease (CBD) is caused by beryllium exposure and is characterized by granulomatous inflammation with accumulation of CD4+ T cells in the lung. We analyzed TCR β-chain and α-chain genes expressed by these CD4+ T cells. In the lungs of individual patients, as well as among four of five CBD patients studied, different oligoclonal expansions within the Vβ3 subset were found to express homologous or even identical CDR3 amino acid sequences. These related expansions were specific for CBD patients, were compartmentalized to lung, and persisted at high frequency in patients with active disease. Limiting dilution cloning and analysis of coexpressed TCR α-chain genes confirmed that these TCRs were selectively expanded by a common Ag involving beryllium. Overall, homologous TCR β- and α-chains showed identical V regions and invariant charged residues within the CDR3 but considerable variability in TCRJ usage. Remarkably, CBD patients expressing nearly identical TCRs did not share common HLA-DRB1 or DQ alleles. These results implicate particular CD4+ cells in the pathogenesis of CBD and provide insight into how beryllium is recognized in human disease.

Identification of pathogenic T cells in patients with beryllium-induced lung disease

Chronic beryllium disease (CBD) is caused by beryllium exposure and is characterized by granulomatous inflammation with accumulation of CD4+ T cells in the lung. We analyzed TCR beta-chain and alpha-chain genes expressed by these CD4+ T cells. In the lungs of individual patients, as well as among four of five CBD patients studied, different oligoclonal expansions within the Vbeta3 subset were found to express homologous or even identical CDR3 amino acid sequences. These related expansions were specific for CBD patients, were compartmentalized to lung, and persisted at high frequency in patients with active disease. Limiting dilution cloning and analysis of coexpressed TCR alpha-chain genes confirmed that these TCRs were selectively expanded by a common Ag involving beryllium. Overall, homologous TCR beta- and alpha-chains showed identical V regions and invariant charged residues within the CDR3 but considerable variability in TCRJ usage. Remarkably, CBD patients expressing nearly identical TCRs did not share common HLA-DRB1 or DQ alleles. These results implicate particular CD4+ cells in the pathogenesis of CBD and provide insight into how beryllium is recognized in human disease.

Selection of hprt mutant T cells as surrogates for dividing cells reveals a restricted T cell receptor BV repertoire in insulin-dependent diabetes mellitus

T cells with somatically acquired mutations in the hypoxanthine-guanine phosphoribosyltransferase (hprt) gene were isolated from patients with insulin-dependent diabetes mellitus (IDDM) as representatives of populations potentially enriched for in vivo activated T cells. TCRB gene V region usage among mutant isolates from individual IDDM patients, but not from normal controls, showed a pronounced preference for BV14 and, to a lesser extent, BV6. Wild-type (nonmutant) isolates did not show such preferences. Extensive in vivo clonal expansions of the BV14 expressing mutant T cells from IDDM patients were revealed by sequence identity of TCRB chain junctional regions. These data support restricted TCRB gene usage in T cell populations enriched for in vivo activated clones in patients with IDDM.

Selective accumulation of related CD4+ T cell clones in the synovial fluid of patients with rheumatoid arthritis

The role of T cells in the pathogenesis of rheumatoid arthritis (RA), especially in the perpetuation of advanced disease, remains unclear. Previous studies have focused on the TCR repertoire of synovial T cells in an attempt to determine whether the pattern of expression is characteristic of Ag-stimulated populations. However, the results of past studies have been conflicting. In the present work, we have undertaken an extensive analysis of the TCRs expressed by CD4+ T cells freshly isolated from synovial fluid of different joints and blood in three patients with established RA. Despite marked heterogeneity of synovial TCR expression, the results showed that 20 to 30% of the TCR beta-chain gene (TCRB) sequences found in one joint were also expressed in a second joint, but not in peripheral blood T cells of the same individual. Analysis of expressed TCRB complementarity-determining region 3 sequences showed the presence of multiple expanded clonal populations that were not predicted by quantitation of beta-chain variable region (Vbeta) expression by immunofluorescence staining. These studies also demonstrated sets of related, but different, complementarity-determining region 3 nucleotide sequences that encoded identical or highly homologous beta-chain amino acid sequences. Analysis of matching T cell clones derived from the joint by limiting dilution culture confirmed coexpression of highly homologous TCR alpha-chain gene (TCRA) and TCRB sequences. Together, these studies suggest that a significant proportion of synovial CD4+ T cells has been selected and expanded by conventional Ag(s) in this disease.

Selective Accumulation of Related CD4+ T Cell Clones in the Synovial Fluid of Patients with Rheumatoid Arthritis

The role of T cells in the pathogenesis of rheumatoid arthritis (RA), especially in the perpetuation of advanced disease, remains unclear. Previous studies have focused on the TCR repertoire of synovial T cells in an attempt to determine whether the pattern of expression is characteristic of Ag-stimulated populations. However, the results of past studies have been conflicting. In the present work, we have undertaken an extensive analysis of the TCRs expressed by CD4+ T cells freshly isolated from synovial fluid of different joints and blood in three patients with established RA. Despite marked heterogeneity of synovial TCR expression, the results showed that 20 to 30% of the TCR β-chain gene (TCRB) sequences found in one joint were also expressed in a second joint, but not in peripheral blood T cells of the same individual. Analysis of expressed TCRB complementarity-determining region 3 sequences showed the presence of multiple expanded clonal populations that were not predicted by quantitation of β-chain variable region (Vβ) expression by immunofluorescence staining. These studies also demonstrated sets of related, but different, complementarity-determining region 3 nucleotide sequences that encoded identical or highly homologous β-chain amino acid sequences. Analysis of matching T cell clones derived from the joint by limiting dilution culture confirmed coexpression of highly homologous TCR α-chain gene (TCRA) and TCRB sequences. Together, these studies suggest that a significant proportion of synovial CD4+ T cells has been selected and expanded by conventional Ag(s) in this disease.

The effect of T-lymphocyte 'clonality' on the calculated hprt mutation frequency occurring in vivo in humans

The frequency of 6-thioguanine resistant (TGr) mutant T-lymphocytes arising in vivo in humans can be quantified with a cell cloning assay. However, the in vivo proliferation of T-lymphocytes that may include TGr mutant cells can distort the relationship between mutation events and the resulting frequency of mutant cells. The T-cell receptor (TCR) gene rearrangement pattern of T-cell colonies can be used as an independent measure of clonality. Analysis of T-cell 'clonality' in 413 wild type and 1736 TGr mutant isolates from 58 individuals shows that mutant clonality is a frequent occurrence (35/58 individuals = 60.3%). However, a major effect on the mutant frequency corrected for clonality (the calculated 'mutation frequency') was found only in nine samples all of which had mutant frequencies greater than 40 x 10(-6).

Measurement of chromosomal aberrations, sister chromatid exchange, hprt mutations, and DNA adducts in peripheral lymphocytes of human populations at increased risk for cancer

Using a multidisciplinary approach, we have measured various indicators of DNA damage in peripheral lymphocytes of human populations potentially at increased risk for cancer. Sister chromatid exchanges (SCE) and polycyclic aromatic hydrocarbon (PAH)-DNA adducts were evaluated in a group of firefighters; chromosomal aberrations and hprt mutations were evaluated in a group of cancer patients undergoing radioimmunoglobulin therapy (RIT); SCE and acrolein-modified DNA were measured in cancer chemotherapy patients and in pharmacists preparing chemotherapy prescriptions; and SCE and PAH-DNA adducts are being measured in U.S. army troops stationed in Kuwait. Our results indicate that both SCE and PAH-DNA adduct levels were not elevated in firefighters, but that other factors such as smoking status and race were risk factors for increased SCE and PAH-DNA adducts. RIT was found to increase background rates of chromosome-type aberrations and frequencies of hprt mutations and there was a strong correlation between levels of therapy-induced chromosome damage sustained in vivo and in vitro sensitivity to radiation-induced chromosome damage. Peripheral blood lymphocytes of cancer patients treated with cyclophosphamide showed higher levels of SCE and had a higher incidence of acrolein adducts in DNA. Lymphocytes from pharmacists preparing antineoplastic drugs were found to acquire increased in vitro sensitivity to SCE induction by phosphoramide mustard with increased lifetime duration of drug handling. A prospective, longitudinal study was performed to identify environmental factors that modulate genetic damage in breast cancer patients. Women with benign breast masses and no apparent disease served as controls. Mutant frequency, cloning efficiency, and chromosomal aberration frequency did not differ significantly among the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of HPRT mutant frequencies in T-lymphocytes from healthy human populations

Somatic cell mutant frequencies at the hprt locus of the X-chromosome were measured with the T-lymphocyte cloning technique in healthy human populations. A statistical analysis was performed of assays from 232 individuals (77 males and 155 females) ranging in age from 19 to 80 years. Data from 4 donor groups were compiled: (a) 132 participants in a study of identical and fraternal twins; (b) 17 health care workers studied as part of an assessment of the risks of handling chemotherapeutic drugs; (c) 62 women with benign breast masses; and (d) 21 normal laboratory and office personnel. The relationship between age and mutant frequency (MF) was expressed by the equation: ln MF = 1.46 + 0.018 age (P < 0.001). Thus, MF increased by about 2% per year. Increases in cloning efficiency (CE) reduced the MF, as shown in the equation: ln MF = 2.91 - 1.32 CE (P < 0.001). CE was significantly related to age (CE = 0.47 - 0.002 age, P = 0.038), and the interdependent relationship between MF, age and CE expressed by the equation: ln MF = 1.99 - 1.13 CE + 0.016 age was significant at the P < 0.001 level. There was no statistically significant effect of donor gender or smoking history on MF in our population, but CE was significantly lower in males (P < 0.001). These findings confirm the importance of age and CE as factors which influence the thioguanine-resistant MF in circulating T-lymphocytes from normal adults.

In vivo ionizing irradiations produce deletions in the hprt gene of human T-lymphocytes

The hprt T-lymphocyte cloning assay, which detects mutations occurring in vivo in humans, has been used to examine mutants induced in patients receiving radioimmunoglobulin therapy (RIT) for cancer. Samples from 13 patients before treatment (controls) and 15 samples from 12 patients after treatment were studied for both mutant frequencies and molecular changes in the hprt mutant T-cell clones. Patients were studied up to 48 months after treatment. Post-RIT patients showed increased mutant frequencies as compared to pre-treatment values. T-cell receptor (TCR) gene analysis of mutant T-cell clones demonstrated that 84% arose independently, both pre- and post-treatment, which is the same proportion as seen in normal individuals. However, several individuals did show large sets of mutants with the same TCR gene rearrangement patterns. Molecular analysis of mutants demonstrated a greater proportion of mutations with hprt gene changes on Southern blots after RIT treatment than before (40% versus 20%). RIT increases the proportion of mutations with total rather than partial gene deletions or other gross structural changes compared to normal individuals or pre-treatment patients. These studies are defining the spectrum for radiation-induced hprt gene mutations in vivo in human T-lymphocytes.

Molecular analysis of in vivo hprt mutations in human T lymphocytes. V. Effects of total body irradiation secondary to radioimmunoglobulin therapy (RIT)

The hprt (hypoxanthine guanine phosphoribosyltransferase) T cell cloning assay was used to detect in vivo mutations in T lymphocytes of individuals receiving radioimmunoglobulin therapy (RIT). A total of 28 patients receiving 131I and/or 90Y-labeled antiferritin antibodies was studied. Mutant frequencies for patients were clearly much higher than for historic non-treated controls (median 68.0 X 10(-6) for patients versus a median of 6.8 X 10(-6) for 115 controls). There was a good correlation of mutant frequency with initial activity of RIT (rlinear = 0.68, rquadratic = 0.76; P less than 0.05) although the correlation of mutant frequency with total activity after several rounds of treatment was poor (R = 0.18). Molecular studies of the hprt mutants demonstrated that a much higher proportion of mutations occurring in RIT treated patients had gross structural alterations of the hprt gene (33%) than did mutations occurring in controls (15%). There was a good correlation (r = 0.72) of mutants with gross alterations and total RIT activity. T cell receptor gene studies demonstrated that most of the mutants (92%) represented independent in vivo mutations, which is similar to previous findings with background mutations in non-irradiated individuals. These studies demonstrate the usefulness of the hprt T cell cloning assay for studies of in vivo human somatic cell gene mutations resulting from ionizing radiation.

Molecular analyses of a Lesch-Nyhan syndrome mutation (hprtMontreal) by use of T-lymphocyte cultures

The frequency of hprt mutants in peripheral blood T-lymphocytes of two putative Lesch-Nyhan individuals and their parents was determined by a cell cloning assay to quantify the frequency of thioguanine-resistant mutants. The results confirmed the Lesch-Nyhan diagnosis and demonstrated that the mother has an elevated mutant frequency consistent with being heterozygous for an hprt mutation. Mass cultures of T-lymphocytes from both the children and their mother, as well as cultures of hprt mutant clones from the mother, were employed as sources of mRNA for cDNA sequence analysis. These hprt mutants show a single base substitution (T----C transition) at position 170 (exon 3). The predicted amino acid change is the substitution of threonine for methionine56. We have designated this new Lesch-Nyhan mutation hprtMontreal. The use of T-lymphocyte cultures allows rapid sequence analyses of hprt mutations, as well as family studies to define the origin of a particular mutation.

In vivo hprt mutant frequencies in T-cells of normal human newborns

Mutation at the hypoxanthine-guanine phosphoribosyl transferase locus (hprt; HPRT enzyme) in the human fetus was studied by clonal assay of placental cord blood samples from full-term newborns. Conditions for determining hprt mutant frequencies, as defined for adults, were also optimal for studies in newborns. The mean mutant frequency for 45 normal human newborns (37 male, 8 female) was 0.64 X 10(-6) (SD = 0.41 X 10(-6); median value = 0.58 X 10(-6). These values are approx. 10-fold lower than corresponding adult hprt mutant frequency values. Factors such as limiting-dilution cloning efficiencies, delay prior to study of sample, sex, cryopreservation or technician performing the assay did not significantly affect assay results. Maternal smoking did not result in elevated mutant frequency values. Most wild-type and mutant clones studied were CD4 surface antigen positive (helper/inducer). All hprt mutants analyzed lacked HPRT activity.