Prognostic significance of uncertain resection for metastasis in the highest mediastinal lymph node after surgery for clinical N0 non-small cell lung cancer

Background

The International Association for the Study of Lung Cancer defined types of surgical resection and considered the positivity of the highest mediastinal lymph node resected a parameter of "uncertain resection" (R-u). We investigated the metastases in the highest mediastinal lymph node, defined as the lowest numerically numbered station among those resected. We aimed to evaluate the prognostic value of R-u compared with R0.

Materials and methods

We selected 550 patients with non-small cell lung cancer at clinical Stage I, IIA, IIB (T3N0M0), or IIIA (T4N0M0) undergoing lobectomy and systematic lymphadenectomy between 2015 and 2020. The R-u group included patients with positive highest mediastinal resected lymph node.

Results

In the groups of patients with mediastinal lymph node metastasis, we defined 31 as R-u (45.6%, 31/68). The incidence of metastases in the highest lymph node was related to the pN2 subgroups (p < 0.001) and the type of lymphadenectomy performed (p < 0.001). The survival analysis compared R0 and R-u: 3-year disease-free survival was 69.0% and 20.0%, respectively, and 3-year overall survival was 78.0% and 40.0%, respectively. The recurrence rate was 29.7% in R0 and 71.0% in R-u (p-value < 0.001), and the mortality rate was 18.9% and 51.6%, respectively (p-value < 0.001). R-u variable showed a tendency to be a significant prognostic factor for disease-free survival and overall survival (hazard ratio: 4.6 and 4.5, respectively, p-value < 0.001).

Conclusions

The presence of metastasis in the highest mediastinal lymph node removed seems to be an independent prognostic factor for mortality and recurrence. The finding of these metastases represents the margin of cancer dissemination at the time of surgery, so it could imply metastasis into the N3 node or distant metastasis.

Non-Lobe Specific Metastases in Occult N2 after Lobectomy for Clinical N0 Non-Small Cell Lung Cancer

OBJECTIVES

Non-small cell lung cancer can spread into lobe specific stations and non-lobe-specific mediastinal lymph nodes. We evaluated frequency and features of non-lobe specific nodal metastases, focusing especially on the prognostic value of only non-lobe specific N2-metastases after lobectomy.

METHODS

We performed a retrospective review of 550 patients with non-small cell lung cancer with clinical N0, undergoing lobectomy and systematic or lobe specific node dissection. We evaluated disease free and overall survival rates using Kaplan-Meier method and significance was tested by log-rank test.

RESULT

Occult N2 disease was detected in 68 patients (8.1%), 26 of them (38.2%) had metastases in non-lobe specific stations. Comparing patients with lobe and non-lobe specific lymph node metastases, 3-years DFS rate was 44.4% vs. 20.0% (p-value = 0.009), while 3-years OS rate was 87.3% vs. 26.7% (p-value <0.001). Among patients with non-lobe specific metastases 16 of them (61.5%) had only non-lobe specific metastases, the remaining 10 patients (38.5%) had metastatic lymph node at the same time in non-lobe specific station but also in lobe-specific stations. Comparing post-operative survival between patients with only non-lobe specific metastases and synchronous lobe and non-lobe specific metastases, 3-years DFS rate was 12.5% vs. 41.3% respectively (p-value = 0.03), and 3-years OS rate was 12.5% vs 76.7% (p-value = 0.002).

CONCLUSION

In patients with occult N2 disease, the finding of a metastatic lymph node in a non-lobe specific station relates with significant lower survival rate. The subset of patients who presented only non-lobe specific node metastases showed a significant lower survival rate compared to the remaining occult N2.

DOG-1 positive primary acinic cell carcinoma of the lung and investigation of molecular status

Primary acinic cell carcinoma (ACC) of the lung is an extremely rare neoplasm that more often arises near to a right bronchus. It is characterized by two populations of clear and dark eosinophilic cells, arranged in a glandular acinar pattern. Mitosis are rare and tumor cells show small and eccentric nuclei. Positive stain for PAS, PAS-D, cytokeratin, A1AT and A1ACT is reported, while TTF1, p40, synaptophysin, SMA, and S100 are substantially negative. DOG-1 positive stain was observed in ACC of the salivary glands and its negativity was proposed to distinguish between primary and metastatic ACC of the lung. Here, we report the 30th case of primary ACC of the lung, describing the immunohistochemical positivity for DOG-1 and the molecular status of the neoplasm for the first time.

Uniportal video-assisted thoracic surgery approach for simultaneous lung cancer and thymic carcinoma: Case report and literature review

Thymic carcinoma is an epithelial tumor derived from thymic epithelial cells. Thymic tumors may be associated with other simultaneous and/or metachronous extra‐thymic tumors (e.g., lung cancer). Here, we report a case of simultaneous surgical management of lung and mediastinal neoplasm together with a review of the literature. During radiological follow‐up for prostate and colorectal cancer, an 82‐year‐old man was diagnosed with lung cancer with simultaneous mediastinal suspected neoplasm. Both were surgically removed with a single intervention performed via a uniportal video‐assisted thoracic surgery (uni‐VATS) approach. The literature emphasizes how extra‐thymic cancer can be diagnosed before, concurrently and consecutively with thymic neoplasia. The surgical treatment of such simultaneous cancer is challenging. We succeeded in the excision of both neoplasia with a mini‐invasive surgical technique. This report highlights the feasibility of uniportal VATS in a patient with very unusual clinical and oncological history.

OP0246 PREDICTIVE VALUE OF LABORATORY AND INSTRUMENTAL FINDINGS IN THE VERY EARLY DIAGNOSIS OF SYSTEMIC SCLEROSIS. ROLE FOR CXCL4 CHEMOKINE

Background:

Systemic sclerosis (SSc) is a rare and progressive autoimmune disease, whose diagnosis is difficult in the early stages because of the lack of specific signs and symptoms. Criteria for a Very Early Diagnosis of SSc (VEDOSS) have been proposed to identify those patients affected by undifferentiated connective tissue disease (UCTD) at risk to develop SSc [1]. For the diagnosis of SSc a strict clinical and laboratory follow up is mandatory [2]. CXCL4 chemokine recently proved to be higher in early SSc [3][4][5].

Objectives:

Aim of our study was to evaluate at baseline the main clinical-demographic and laboratory parameters in a group of VEDOSS patients, comparing these features during the follow-up, to detect any difference between progressors (P) and non-progressors (NP) into SSc. Furthermore, we dosed plasma levels of CXCL4.

Methods:

We included 27 VEDOSS patients, defined by EUSTAR 2011 Criteria and not fulfilling the 2013 ACR/EULAR classification criteria of SSc, attending the Rheumatology Unit of Policlinico Umberto I in Rome from 2009 to 2020. Demographic, laboratory and instrumental features were analyzed, and, after a mean follow-up of 5.7±1,7 years, we compared the P to NP patients. Having obtained written informed consent, blood samples were taken at baseline to measure plasma levels of CXCL4 chemokine using an ELISA assay.

Results:

At baseline the 27 VEDOSS patients (mean age 53.2±13.5 years, all females) had ANA positivity in 25 (93%) cases and Raynaud’s phenomenon in 25 (93%) cases. In a mean follow-up time of 43.5 ± 23.1 weeks from the first clinical examination, 15 (55%) patients were classified as P into SSc. These P patients showed a significant association with SSc specific antibodies such as anti-Centromere, anti-Scl70 and anti-RNAPIII (p=0.014) as well as with a specific “Scleroderma pattern” at the nailfold capillaroscopy (p=0.022) respect to those NP into SSc. A group of 6 P patients evolved in less than 24 months (mean 19,6 ± 6,8 weeks) and were defined “Fast Progressor”. They were also significantly associated with those autoantibodies considered as having a worse prognosis such as anti-Scl70 and anti-RNAPIII (p=0.005), and had a shorter duration of RP (88 vs 189.3 months) and a younger mean age (49.5 vs 55.4 years) respect to “Slow Progressor” (SSc evolving in >24 months). At baseline we detected significantly higher median plasma levels of CXCL4 in the 27 VEDOSS patients compared to 10 healthy subjects (9024±10559 pg/ml versus 348,5±684,3 pg/ml; p=0.0047). We also noticed a trend for lower CXCL4 levels in the “Fast Progressor” than in the “Slow Progressor” (3303 ± 6065 pg/ml vs 13300 ± 10308 pg/ml; p=0.052) without reaching a significant value, due probably to the low number of cases.

Conclusion:

Our study confirms that the presence of specific autoantibodies and capillaroscopic abnormalities correlate to an increased risk of developing SSc in patients with UCTD [6]. Beside we found significantly higher levels of CXCL4 in our 27 VEDOSS patients respect to controls, in agreement with other authors showing the association of this chemokine with early stages and specific organ involvement [4][5][7]. The finding of CXCL4 lower levels in “fast progressor” cases is consistent with our recent report of anti-CXCL4 antibodies in patients with early SSc, determining lower levels of this antigen [7]. We need deeper investigations to better evaluate the role of CXCL4 in the different stages of SSc.

References:

[1]J. Avouac et al., Ann. Rheum. Dis., 2011.

[2]F. van den Hoogen et al., Ann. Rheum. Dis., 2013.

[3]G. Valentini et al., Clin. Exp. Med., 2017.

[4]R. Lande et al., Nat. Commun., 2019.

[5]L. van Bon et al., N. Engl. J. Med., 2014.

[6]M. Vasile et al., Clin. Exp. Rheumatol., 2018.

[7]R. Lande et al., Int. J. Mol. Sci., 2020.

Disclosure of Interests:

None declared

Hobnail variant of papillary thyroid carcinoma showing goiter-like presentation and rapid growth

SUMMARY

We present the case of a 47-year-old Caucasian previously healthy woman with a voluminous thyroid nodule occupying almost the entire anterior neck region. The lesion had progressively increased in size during the previous 3 months and the patient presented intermittent symptoms of dysphagia and odynophagia with a slight change in voice. Fine needle aspiration showed papillary carcinoma. Based on imaging and cytological findings, the patient underwent total thyroidectomy. The surgical sample revealed a totally enlarged thyroid gland (weight: 208 g) with the presence of a poly-lobulated lesion centrally located and involving the isthmus and both lobes. Hobnail features were present in more than 30% of the neoplastic cells in agreement with the criteria for this subtype. Psammoma bodies and focal necrosis were also present. The extra-thyroidal extension included strap muscles and peri-esophageal glands. Immunohistochemistry using VE1 antibody for detecting BRAF-V600E mutation resulted positive. The final diagnosis was papillary thyroid carcinoma (PTC) hobnail variant (HVPTC)-pT4a. The HVPTC is a rare entity and, in most cases, appears like a unifocal lesion with a maximum tumor size of 8 cm reported so far. To our knowledge, this represents the largest tumor ever described (14 cm), showing rapid growth and with multinodular goiter-like aspect.

LEARNING POINTS

HVPTC is an aggressive variant of PTC, usually associated with radioactive iodine refractoriness, and a higher mortality rate compared to classic PTC. However, there is a marked individual variability in this association. HVPTC usually appears as small unifocal lesion but a multinodular goiter presentation may occur. The present case highlights that despite of the histology, our patient achieved a high ablation success rate after radioactive iodine therapy.

Focus on the pulmonary involvement and genetic patterns in Birt-Hogg-Dubè syndrome: Literature review

INTRODUCTION

Brit-Hogg-Dubé syndrome (BHD) is a rare disorder that is estimated to affects about 600 families in the World. The disease-causing mutations is on FLCN gene which codes for folliculin. This protein has a role in different organs as skin, kidney and lung, thanks to the interaction with type I and II cadherins, RhoA activity and the regulation of AMPK, mTORC1 pathways and cell adhesion. The aim of our study is to focus on the manifestation of the syndrome, especially the pulmonary involvement, then on genetical analysis and on the available treatments.

MATERIAL AND METHODS

We collected 15 previous studies where we found medical history information, clinical manifestations, radiological and histological diagnosis and genetical analysis.

RESULTS

The prevalence of pneumothorax in patients with BHD syndrome was about 65%, but the lung involvement with multiple small cysts, localized especially in the lower part, was 85%. The prevalence of renal involvement in BHD patients ranged from 6.5% to 34%, while skin lesions ranged from 11% to 50%. More than 150 FLCN germline has been described, though the mutation in exon 11 is the most frequently detected, especially among Caucasian population.

CONCLUSIONS

BHD syndrome is rare and usually the first manifestations appear in early age. In patients with these clinical and radiological characteristics we suggest taking a careful medical history, though the diagnosis of BHD syndrome should be confirmed with the analysis of FLCN gene.

Toll-like receptors in mediating pathogenesis in systemic sclerosis

Toll-like receptors (TLRs) are evolutionarily conserved receptors essential for the host defence against pathogens. Both immune and non-immune cells can express TLRs, although at different levels. Systemic sclerosis (SSc) is a chronic disease in which autoimmunity, dysregulated profibrotic mediator release and activation of fibroblasts lead to dysregulated collagen deposition and fibrosis. There is now increasing knowledge that the innate immune system and, in particular, TLRs take a part in SSc pathogenesis. The list of endogenous ligands that can stimulate TLRs in SSc is growing: these ligands represent specific danger-associated molecular patterns (DAMPs), involved either in the initiation or the perpetuation of inflammation, and in the release of factors that sustain the fibrotic process or directly stimulate the cells that produce collagen and the endothelial cells. This review reports evidences concerning TLR signalling involvement in SSc. We report the new DAMPs, as well as the TLR-linked pathways involved in disease, with emphasis on type I interferon signature in SSc, the role of plasmacytoid dendritic cells (pDCs) and platelets. The dissection of the contribution of all these pathways to disease, and their correlation with the disease status, as well as their values as prognostic tools, can help to plan timely intervention and design new drugs for more appropriate therapeutic strategies.

Ectopic thoracic thyroid removed by uniportal VATS approach. A case report

•

VATS technique is minimally invasive and, moreover, it is characterized by a shorter recovery period, a minor blood loss and a shorter hospital stay.

•

We speak of “Ectopic thyroid gland” when a piece of thyroid tissue is placed at a certain distance from the second to fourth tracheal cartilages.

•

This case report aims at describing the successful extraction of a massive piece of ectopic thyroid from a young woman’s body, thanks to uniportal VATS.

Introduction

We speak of “Ectopic thyroid gland” when a piece of thyroid tissue is placed at a certain distance from the second to fourth tracheal cartilages.

Presentation of case

This case report focuses on a case of a hyperplastic cystic nodule of ectopic thyroid in a 30-year-old woman treated with uniportal video-assisted thoracic surgery (VATS). The patient, was admitted to Emergency Unit for abdominal pain and vomit, underwent a CT which highlighted a mass of significant dimension on the right side of the mediastinum, in contact with close structures. The lesion has been removed with an innovative mini-invasive technique, which is characterized, differently from traditional surgical approaches, by reduced loss of blood and time of hospitalization and, in addiction to that, an aesthetic small-dimensioned scar.

Discussion

VATS technique is minimally invasive and, moreover, it is characterized by a shorter recovery period, a minor blood loss and a shorter hospital stay. VATS has been advocated since 2010 for pulmonary resections, but today it is also performed for mediastinal intervention and a series of reports have demonstrated that it is feasible and safe.

Conclusion

The report aims at pointing out the possibility of undergoing this kind of surgery not only in case of pulmonary mass (on which the previous literature has focused) but also when mediastinum lesions occur, as in our case.

Awake thoracoscopic bullaplasty

OBJECTIVE

Staple excision of emphysematous bullae through general anesthesia is the standard surgical treatment of bullous emphysema. We have developed a new surgical technique entailing thoracoscopic bullaplasty performed in fully awake patients through sole epidural anesthesia.

METHODS

This prospective nonrandomized trial included 35 patients undergoing awake thoracoscopic bullaplasty between 2002 and 2009. Preoperative work-up included computed tomography with algorithm for quantitative measurement of the bulla volume. Outcome measures included patient's satisfaction with the anesthesia, scored into four grades (1=unsatisfactory; 4=excellent); ratio of arterial oxygen tension to fraction of inspired oxygen (PaO(2)/FiO(2)), and postoperative assessment of standard clinical measures at 6, 12, and 36 months.

RESULTS

There were 29 men and six women with a median age of 60 years. Median volume of the bulla was 688 ml. Awake bullaplasty was successfully completed in 34 patients. Perioperatively, PaO(2)/FiAO(2) decreased significantly (analysis of variance (ANOVA), P<0.0001) though remaining satisfactory (>300 mmHg), whereas PaCO(2) increased intraoperatively (ANOVA, P<0.0001) but returned to baseline values 1h after surgery (P=0.20). There was no mortality; four patients had air leaks longer than 7 days. Mean hospital stay was 4.9 ± 2.2 days. Comparisons between pre- to 6-month changes in outcome measures showed improvements (P<0.0001) in forced expiratory volume in 1s (FEV(1)) (+0.37 l), residual volume (-1.16 l), dyspnea index (-2), and standard 6-min walk test (SMWT) (+71 m). These improvements lasted for up to 36 months and in no patient did operated bullae recur.

CONCLUSION

Our study suggests that awake thoracoscopic bullaplasty was well tolerated and easily performed in the majority of the patients, and significant clinical improvements lasted for up to 36 months.

Effects of lung volume reduction surgery for emphysema on glycolipidic hormones

BACKGROUND

Pulmonary emphysema is associated with cachexia and disregulation of the hormones regulating the glycolipid metabolism, insulin resistance, and altered substrate utilization. This study aimed at identifying the effects of lung volume reduction surgery (LVRS) on glycolipidic hormones compared to respiratory rehabilitation (RR).

METHODS

Thirty-three patients with moderate-to-severe emphysema who were undergoing video-assisted thoracoscopic LVRS were compared to 31 similar patients who refused the operation and followed a standardized RR program. All patients were evaluated before and 12 months after treatment for respiratory function, body composition, glycolipidic hormones, metabolic parameters, and insulin resistance, which was calculated using the homeostatic model assessment index for insulin resistance (HOMA-IR). These groups were compared to a matched healthy control population.

RESULTS

Only after LVRS significant improvements were obtained in respiratory function (FEV1, +25.2%; p<0.0001; residual volume, -19.5%; p<0.0001), metabolic parameters (total cholesterol, +13.1%; p<0.01; high-density lipoprotein cholesterol, +11.2%; p<0.01; triglycerides, +18.4; p<0.001; nonesterified fatty acid, -19.7%; p<0.001), and body composition (fat-free mass [FFM], +6.5%; p<0.01; fat mass [FM], +11.9%; p<0.01). The leptin/FM ratio (-6.1%; p<0.01) and resistin/FM ratio (-5.6%; p<0.01) decreased, whereas the adiponectin/FM ratio (+6.9%; p<0.01) and ghrelin (+9.2%; p<0.01) increased, together with reductions in glycemia (-8.8%; p<0.01), insulin level (-20.4%; p<0.001), and HOMA-IR (-27.2%; p<0.0001). The decrement in residual volume was correlated with increment of FFM (rho=-0.49; p<0.02), FM (rho=-0.55; p<0.009), and ghrelin (rho=-0.52; p<0.01), and also with decreases in leptin corrected for FM (rho=0.50; p<0.02) and, marginally, HOMA-IR (rho=0.35; p=0.07).

CONCLUSIONS

After LVRS, glycolipidic hormone levels and nutritional status significantly improved, along with insulin resistance reduction and more physiologic utilization of substrates. Correlations between residual volume and body composition as well as glycolipidic hormone levels suggest that postoperative recovery in respiratory dynamics may induce favorable clinical changes when compared to RR.

Both maturation and survival of human dendritic cells are impaired in the presence of anergic/suppressor T cells

T cell suppression is a well established phenomenon, but the mechanisms involved are still a matter of debate. Mouse anergic T cells were shown to suppress responder T cell activation by inhibiting the antigen presenting function of DC. In the present work we studied the effects of co-culturing human anergic CD4⁺ T cells with autologous dendritic cells (DC) at different stages of maturation. Either DC maturation or survival, depending on whether immature or mature DC where used as APC, was impaired in the presence of anergic cells. Indeed, MHC and costimulatory molecule up-regulation was inhibited in immature DC, whereas apoptotic phenomena were favored in mature DC and consequently in responder T cells. Defective ligation of CD40 by CD40L (CD154) was responsible for CD95-mediated and spontaneous apoptosis of DC as well as for a failure of their maturation process. These findings indicate that lack of activation of CD40 on DC by CD40L-defective anergic cells might be the primary event involved in T cell suppression and support the role of CD40 signaling in regulating both activation and survival of DC.

Peptide analogues as a strategy to induce tolerance in T cells with indirect allospecificity

BACKGROUND

It has been demonstrated that indirect recognition of allogeneic MHC molecules might play an important role in provoking graft rejection. Although direct recognition of allogeneic molecules on antigen presenting cells of the graft may induce a state of tolerance, the continuous presentation of processed alloantigens by specialized antigen presenting cells does not allow the same phenomenon to occur. Tolerance to interleukin-2 secreting T cells can be achieved in different ways, among these is the exposure to mutants of the wild type allopeptide. We have investigated whether peptide analogues of the allopeptide can induce tolerance in T cells with indirect allospecificity.

METHODS

T cell clones with indirect anti-HLA-A2-specificity generated from a HLA-A2-DRB1*1502+ patient who chronically rejected a HLA-A2-expressing kidney allograft were used for this study. Nine peptide analogues of HLA-A2 (residues: 103-120) were produced with single amino acid substitutions at the putative T cell receptor for antigen contact positions. Their effect on the proliferation of a panel of T cell clones was evaluated.

RESULTS

Peptide analogues and wild type peptide had similar capacity to bind to the restriction molecule HLA-DRB1*1502. Co-presentation of the peptide analogues 111R/A, H, K and 114H/K, with the wild type peptide inhibited T cell responses, indicative of antagonism. In addition, one analogue 112G/S induced unresponsiveness in the T cells to subsequent culture with the wild type peptide.

CONCLUSIONS

The data presented here suggest that using reagents such as altered peptides may represent a strategy to prevent the activation of T cells with indirect alloreactivity and allograft rejection in vivo.

Significant frequencies of T cells with indirect anti-donor specificity in heart graft recipients with chronic rejection

BACKGROUND

The purpose of this study was to determine whether T cells with indirect allospecificity could be detected in heart transplant recipients with chronic rejection.

METHOD AND RESULTS

Human T-cell clones were used to determine the most effective way to deliver major histocompatibility complex alloantigens for indirect presentation. Seven allograft recipients with evidence of progressive, chronic rejection were selected. Four heart graft recipients with no evidence of chronic rejection were used as controls. Peripheral blood T cells and antigen-presenting cells from the recipients were cultured with frozen/thawed stored donor cells or major histocompatibility complex class I-derived synthetic peptides in limiting dilution cultures and then compared with controls using tetanus toxoid and frozen/thawed third-party cells with no human leukocyte antigens in common with the donor. In 5 of 7 patients analyzed who had chronic rejection, elevated frequencies of T cells with indirect, anti-donor specificity (iHTLf) were detected. No such elevated iHTLf were detected in recipients without chronic rejection.

DISCUSSION

iHTLf can be obtained from human transplant recipients, which supports the contention that the indirect pathway is involved in chronic transplant rejection.

Lack of T cell proliferation without induction of nonresponsiveness after antigen presentation by endothelial cells

BACKGROUND

After priming or reactivation in lymph nodes, T cells recirculate to sites of inflammation, and enter tissues by migrating across activated endothelium. Given that activated endothelial and tissue parenchymal cells express both class I and class II MHC molecules, it is probable that transmigrating T cells encounter cognate antigen on endothelial cells, and on tissue parenchymal cells once they have entered the tissue.

METHODS

In this study the consequences of antigen presentation by endothelial and epithelial cells to human CD4+ T cell clones were analyzed and compared by a two-step culture system.

RESULTS

T cell clones that required B7-mediated costimulation to be activated were found not to be able to proliferate to antigen presented by either endothelial or epithelial cells, unless trans-costimulation was provided by the addition of B7-transfected cells in the cultures. Furthermore, antigen presentation by epithelial cells induced nonresponsiveness in the T cell clones. In contrast, after cognate recognition on endothelial cells, the ability of the T cell clones to proliferate to a subsequent rechallenge with antigen presented on a specialized APC was unaffected.

CONCLUSIONS

These data suggest that endothelial cells have unique properties as antigen-presenting cells, in that they do not influence the subsequent reactivity of cognate T cells.

Hypervariable region 1 variants act as TCR antagonists for hepatitis C virus-specific CD4+ T cells

In various human viral infections, the appearance of mutated epitopes displaying TCR antagonistic activity has been correlated with the severity and persistence of infection. In hepatitis C virus (HCV) infection, where the virus persistence has been associated with the rapid and substantial Ag modifications occurring during replication, TCR antagonism has been evidenced in CD8+ T cell responses. However, CD4+ T cell antagonism may be another important strategy by which HCV eludes a protective response, because sustained Th responses directed against several HCV Ags are associated with a self-limited course of infection. The data reported here represent the first evidence that variants of the hypervariable region (HVR1) of the putative Envelope 2 protein of HCV can act as powerful TCR antagonists for HVR1-specific CD4+ T cells isolated from HCV-infected individuals. Using classical antagonism assays, we observed strong inhibition of cellular proliferation and cytokine production when the agonist and the antagonist ligands were simultaneously presented by the same APCs. The presence in HVR1 of conserved residues, critical for binding to HLA-DR molecules, supports the function of HVR1 variants as TCR antagonists. In conclusion, our data evidence an antagonism phenomenon, which was achieved by naturally occurring class II-restricted T cell epitopes whose mechanism was addressed in terms of the antagonist capacity to inhibit agonist-mediated TCR down-regulation and early signal transduction.

Antigen recognition influences transendothelial migration of CD4+ T cells

The functional significance of MHC class II expression by vascular endothelial cells remains obscure. In this study the possibility that Ag presentation by endothelial cells (EC) influences T cell transmigration, facilitating the recruitment of Ag-specific T cells into tissues, was investigated. The frequencies of T cells with specificity for an HLA-DR alloantigen, or for the recall Ag tetanus toxoid (TT), were measured in peripheral blood CD45RO+ (memory) CD4+ T cells before and after transmigration through gamma-IFN-treated EC monolayers. Frequencies of anti-DR17, IL-2-secreting T cells were fourfold higher in the T cells that transmigrated through a monolayer of DR17-expressing EC. Similar increases were seen in TT-specific, DR7-restricted T cells that transmigrated through TT-pulsed, DR7-expressing EC. To examine more directly the effects of cognate recognition of Ag presented by EC, T cell clones were used. For clones that proliferated in a costimulation-independent manner to Ag presented by EC, cognate recognition arrested transmigration. In contrast, Ag presentation by EC to B7-dependent T cell clones, which do not proliferate following cognate recognition of EC, enhanced the rate of transendothelial migration. These data suggest that Ag presentation by EC may serve to augment the recruitment of Ag-specific T cells into tissues and that proliferation and transmigration are mutually exclusive T cell responses.

CD4+ T cells orchestrate both amplification and deletion of CD8+ T cells

This review focuses on the role of CD4+ T cells in regulating immune responses, orchestrating both the amplification and deletion of immune cells, particularly CD8+ T cells. These two functions, which represent only an apparent contradiction, appear to be two faces of the same process of regulation. In fact, because the immune response, once activated, needs to be carefully controlled or switched off when the antigenic stimulus is eliminated, the immune system has developed several strategies either to regulate clonal amplification or to avoid useless expansion of activated cells. In particular, we have reported many data demonstrating that CD4+ T cells may be indicated as the regulatory element in the activation as well as the deletion of CD8+ T cells. New data are also reported on the ability of anergic CD4+ T cells to suppress CD8+ T-cell activation through induction of apoptosis, and on the need for CD8+ T cells for antigen recognition in inducing cell death in CD4+ T cells. Moreover, the central role of CD4+ T cells in the maintenance of peripheral tolerance has been widely described.

Role of donor and recipient antigen-presenting cells in priming and maintaining T cells with indirect allospecificity

BACKGROUND

It has been suggested that the sensitization of recipient T lymphocytes against peptides derived from allogeneic major histocompatibility complex (MHC) antigens in the context of self-MHC molecules may contribute to the pathogenesis of chronic allograft rejection. The purpose of this study was to quantitate and characterize the indirect alloresponse in renal transplantation.

METHODS

An HLA-A2-negative patient whose A2-positive kidney transplant failed as a result of chronic rejection was selected for this study. T-cell clones were raised using a cocktail of peptides corresponding to polymorphic regions of the A2 sequence and studied by measuring their proliferation using [3H]thymidine incorporation. The presence in vivo of HLA-A2-specific T cells was assessed using limiting dilution analysis.

RESULTS

T-cell clones were specific for a single peptide of HLA-A2, residues 92-120, and restricted by HLA-DRB1*1502. The frequency of interleukin-2-secreting T cells specific for this A2 peptide was 1:86,000, only 2-fold lower than that measured against the recall antigen tetanus toxoid. Capitalizing on the similarity of the donor and recipient DR15 alleles (DRB1*1501 and 1502), the question was addressed as to how these T cells had been primed in vivo. Although the large majority of clones responded to A2 synthetic peptide presented by both DR15 alleles, only 3 of 10 clones responded to cells co-expressing DRB1*1501 and A2.

CONCLUSION

These data suggest that antigen presentation by recipient APCs is responsible for maintaining T cells with indirect allospecificity in vivo and that, in the context of partial DR matching, indirect presentation by the parenchymal cells of the graft may serve to induce tolerance in T cells with indirect allospecificity.

Interferon-gamma-treated renal tubular epithelial cells induce allospecific tolerance

Following organ transplantation, tissue parenchymal cells commonly express major histocompatibility complex (MHC) class II molecules as a result of local cytokine release, and thus acquire the capacity to present donor MHC alloantigens to alloreactive CD4+ T cells. The consequences of such a presentation are likely to be relevant in the induction of tolerance to the transplanted tissues, and this has been reported in animal models of transplantation and in humans. In this study, the consequences of antigen presentation by interferon-gamma (IFN-gamma)-treated human renal tubular epithelial cells (RTEC) to resting and activated CD4+ T cells were investigated. Allogeneic RTEC were unable to stimulate proliferation by peripheral blood CD45 RA+ or RO+ CD4+ T cells from three HLA-mismatched responders. The response to RTEC was partially reconstituted by the addition of murine L cell transfectants expressing human B7.1 (DAP.3-B7), suggesting that the failure of RTEC to stimulate a primary alloresponse was due, at least in part, to a lack of costimulation. T cell clones dependent on B7-mediated co-stimulation also did not respond to peptide presented by RTEC. Most importantly, this lack of reactivity was accompanied by the induction of nonresponsiveness. Incubation with allogeneic, DR-expressing RTEC induced allospecific hyporesponsiveness in both CD45RA+ and RO+ cells. Similarly, overnight incubation with antigen-pulsed RTEC induced nonresponsiveness in the B7-dependent T cell clones. These results suggest that MHC class II expression on RTEC may contribute to the induction of an allospecific nonresponsiveness following organ transplantation.

Antigen presentation by epithelial cells induces anergic immunoregulatory CD45RO+ T cells and deletion of CD45RA+ T cells

The immunoregulatory effects of alloantigen presentation by tissue parenchymal cells to resting peripheral blood CD4+ T cells was investigated. Coculture of CD45RO+ (memory) and CD45RA+ (naive) T lymphocytes with primary cultures of MHC class II-expressing epithelial cells rendered both populations of T cells hyporesponsive to a subsequent challenge by the same MHC molecule expressed on EBV-transformed lymphoblastoid B cell lines. However, the mechanisms responsible for the allospecific hyporesponsiveness were distinct. For the CD45RO+ T cells, responsiveness was restored by subsequent culture in the presence of IL-2; the addition of IL-2 had no effect on the reactivity of the CD45RA+ T cells. In contrast, the naive T cells were protected from the induction of nonresponsiveness by the presence of a neutralizing anti-CD95 Ab during the culture with thyroid follicular cells. In addition, the hyporesponsive CD45RO+ T cells effected linked suppression, in that they inhibited proliferation against a third-party DR alloantigen when the third-party alloantigen was coexpressed with the DR Ag against which hyporesponsiveness had been induced. These results suggest that recognition of Ag by T cells on tissue parenchymal cells plays an important role in the maintenance of peripheral T cell tolerance, inducing nonresponsiveness in naive and memory T cells by distinct mechanisms.

Antigen presentation by epithelial cells induces anergic immunoregulatory CD45RO+ T cells and deletion of CD45RA+ T cells

The immunoregulatory effects of alloantigen presentation by tissue parenchymal cells to resting peripheral blood CD4+ T cells was investigated. Coculture of CD45RO+ (memory) and CD45RA+ (naive) T lymphocytes with primary cultures of MHC class II-expressing epithelial cells rendered both populations of T cells hyporesponsive to a subsequent challenge by the same MHC molecule expressed on EBV-transformed lymphoblastoid B cell lines. However, the mechanisms responsible for the allospecific hyporesponsiveness were distinct. For the CD45RO+ T cells, responsiveness was restored by subsequent culture in the presence of IL-2; the addition of IL-2 had no effect on the reactivity of the CD45RA+ T cells. In contrast, the naive T cells were protected from the induction of nonresponsiveness by the presence of a neutralizing anti-CD95 Ab during the culture with thyroid follicular cells. In addition, the hyporesponsive CD45RO+ T cells effected linked suppression, in that they inhibited proliferation against a third-party DR alloantigen when the third-party alloantigen was coexpressed with the DR Ag against which hyporesponsiveness had been induced. These results suggest that recognition of Ag by T cells on tissue parenchymal cells plays an important role in the maintenance of peripheral T cell tolerance, inducing nonresponsiveness in naive and memory T cells by distinct mechanisms.

Anergic T cells effect linked suppression

Although the phenomenon of T cell-mediated suppression is well established, particularly in experimental models of transplantation, the mechanisms involved in this form of immunoregulation remain controversial. We have recently demonstrated, using an in vitro system, that anergic T cells can act as suppressor cells by competing for the membrane of the antigen-presenting cell (APC) and for locally produced interleukin-2. In the experiments described here we have explored the ability of anergic T cells to effect linked suppression in antigen-specific and allospecific responses. We observed that anergic antigen-specific CD4+ T cells can inhibit T cells restricted by a different major histocompatibility complex (MHC) class II molecule provided that both restriction elements are expressed by the same APC. In addition, anergic allospecific clones could also effect linked suppression since they could regulate not only T cells specific for the same alloantigen but also responder T cells with direct allospecificity for a second allogeneic MHC molecule or with indirect, self MHC-restricted allospecificity for a processed MHC class I alloantigen. Furthermore, the regulatory effect of the anergic T cells was dependent on cell contact, was not dependent upon irradiation, and was maintained during in vitro culture. These data demonstrate that linked suppression can be effected by anergic T cells in vitro. In the clinical context this raises the possibility that induction of tolerance to a single alloantigen could serve to regulate the immune response to an allograft carrying several MHC and minor antigen differences.

S-100 protein positivity in breast carcinomas: a potential pitfall in diagnostic immunohistochemistry

S-100 protein, originally isolated from neural tissues, has also been identified in various normal and neoplastic cells, including malignant melanomas. A systematic immunohistochemical investigation of this antigen was performed on formalin-fixed paraffin-embedded samples of benign and malignant breast tissues with use of the avidin-biotin-peroxidase complex immunoperoxidase technique and a polyclonal antiserum that recognizes both the alpha and beta subunits of S-100 protein. In benign breast tissue, S-100 protein was present in both epithelial and myoepithelial cells of terminal ducts and lobules; the staining was cytoplasmic and sometimes nuclear. Of 100 randomly selected invasive breast carcinomas, 48 per cent contained S-100 protein-positive tumor cells. Lobular and medullary carcinomas (60 per cent and 80 per cent, respectively) were more frequently positive than ductal carcinomas (45 per cent). Dendritic cells, most likely Langerhans' cells, were present in some carcinomas and were also positive for S-100. There was no relationship of S-100 positivity to histologic differentiation, recurrence interval, or the expression of various tumor markers. The presence of S-100 protein positivity in metastatic breast carcinomas may lead to the erroneous diagnosis of malignant melanoma. Our observations underscore the importance of testing for a broad panel of tumor markers rather than relying on single antigens in evaluating metastatic malignancies of undetermined origin.