Role of CD4+ T lymphocytes in antitumor immunity

Primary Sjögren's syndrome and B-non-Hodgkin lymphoma: role of CD4+ T lymphocytopenia

Primary Sjögren's syndrome (PSS) is associated with increased risk of lymphoproliferative malignancy, and B-cell non-Hodgkin lymphoma (B-NHL) is the most frequent type. To evaluate CD4+ T lymphocytes distributions in patients with (PSS) and the association of CD4+ T lymphocytopenia with the development of (B-NHL), this study included 8 (PSS) patients associated with B-NHL (group I), 50 (pSS) patients without B-NHL (group II), and 30 healthy volunteers who served as controls. The frequency of circulating CD4+ and CD8+ T lymphocytes distributions and CD4+/CD8+ T cell ratio was assessed using flow cytometry coulter EPICS-XL and compared between patients groups and controls. There was statistically significant CD4+ T lymphocytopenia in (PSS) patients with B-NHL than those without lymphoma and controls (P = 0.001). Moreover, a significant low CD4+/CD8+ T cell ratio 0.8 in group I than group II and controls (P = 0.001) was found. Significant positive correlations of CD4+ T lymphocytopenia with other risk factors (parotid swelling, vasculitis, rheumatoid factors, low complement, cryoglobulinemia) were detected. CD4+ T lymphocytopenia is associated with B-NHL developed in patients with PSS and can be considered as an important predictor of lymphoma.

T-cell epitope peptide vaccines

T-cell immunotherapy is a promising treatment option for cancer. The identification of tumor antigens that are recognized by the immune system has allowed for the generation of vaccines for various malignancies. Due to the ease of manufacturing and characterizating peptide-based vaccines they have been used to stimulate antitumor T-cells. This article will review the use of peptide-based vaccines for the treatment of cancer by inducing antitumor T-lymphocyte responses.

Lymphoma and other malignancies in primary Sjögren's syndrome: a cohort study on cancer incidence and lymphoma predictors

OBJECTIVES

To assess the risk of lymphoproliferative disease or other malignancy (standardised incidence ratios (SIRs)), in patients with primary Sjögren's syndrome according to the American-European Consensus Criteria (AECC), compared with patients with sicca syndrome (non-AECC) and the background population. To identify predictors of malignancy and describe lymphoma types and survival probabilities.

METHODS

A linked register study using information from the Malmö Primary SS Register, Swedish Cancer Register, and Cause-of-Death Register for calculation of SIRs was carried out. Detected lymphomas were reclassified according to the WHO classification. Cox regression analysis was used to study the predictive value of clinical, laboratory, and histological findings at the time of diagnosis.

RESULTS

507 patients with a median follow up of 8 years (range 1 month to 19 years) were included. SIRs (95% confidence interval (CI)) for malignancies in total and for non-Hodgkin's lymphomas (NHL) were 1.42 (0.98 to 2.00) and 15.57 (7.77 to 27.85), respectively, in those fulfilling the AECC (n = 286). In non-AECC sicca patients (n = 221) SIR for malignancy of any kind was 0.77 (0.41 to 1.32); no lymphoproliferative neoplasms were detected. Significant predictors of lymphoproliferative disease were purpura/skin vasculitis (hazard ratio (HR) = 4.64, 95% CI 1.13 to 16.45), low complement factor C3 (HR = 6.18, 95% CI 1.57 to 24.22), low C4 (HR = 9.49, 95% CI 1.94 to 46.54), CD4+ T lymphocytopenia (HR = 8.14, 95% CI 2.10 to 31.53), and a low CD4+/CD8+ T cell ratio < or = 0.8 (HR = 10.92, 95% CI 2.80 to 41.83). 7/12 (58%) NHLs were diffuse large B cell lymphomas.

CONCLUSION

A 16-fold increased risk for development of NHL was found. CD4+ T lymphocytopenia is an additional strong risk factor for developing lymphoma.

Fine-tuning of helper T cell activation and apoptosis by antigen-presenting cells

The role of antigen-presenting cells (APC) in regulating helper T cell responses and activation-induced cell death (AICD) was investigated in vitro. T cell activation was monitored by measuring the early rise of intracellular free calcium [Ca+]ic, mRNA and cell surface expression of activation and apoptotic molecules, the production of cytokines and the activation of transcription factors. Our results demonstrate that the unique characteristics of a given APC can modify the threshold, kinetics and magnitude of the T cell response. The rapid and sustained rise of intracellular free calcium correlated well with the extent of cytokine production and the expression of activation molecules. Fas-dependent AICD could be induced by the most potent antigen-presenting cell (2PK3) only. Our results demonstrate that the response and fate of effector/memory CD4+ helper T lymphocytes is highly dependent on the individual properties of the APC they encounter.

Targeting dendritic cells for priming cellular immune responses

The cardinal role of dendritic cells (DC) in priming adaptive immunity and in orchestrating immune responses against all classes of pathogens and also against tumors is well established. Their unique potential both to maintain self-tolerance and to initiate protective immune responses against foreign and/or dangerous structures is based on the functional diversity and flexibility of these cells. Tissue DC lining antigenic portals such as mucosal surfaces and the skin are specialized to take up a wide array of compounds including proteins, lipids, carbohydrates, glycoproteins, glycolipids and oligonucleotides, particles carrying such structures and apoptotic or necrotic cells. This process is facilitated by specialized receptors with high endocytic capacity, which provides potential targets for delivering designed molecules. The best route for targeting B- and/or T cell epitopes, however, is still the subject of intense investigation. Immature DC, which reside in various tissues, can be activated by pathogens, stress and inflammation or modified metabolic products, which induce mobilization of cells to draining lymph nodes where they act as highly potent professional antigen presenting cells. This is brought about by the ability to present their accumulated intracellular content for both CD4+ helper (Th) and CD8+ cytotoxic/cytolytic T lymphocytes (Tc/CTL). Engulfed proteins are processed intracellularly and their peptide fragments are transported to the cell surface in the context of major histocompatibility complex encoded class I and II molecules for presentation to Th cells and CTLs, respectively. The T cell priming capacity of DC, however, depends not only on antigen presentation but also on other features of DC. Human monocyte-derived DC provide an excellent tool to study the internalizing, antigen-presenting and T cell-activating functions of DC at their immature and activated differentiation states. These biological activities of DC, however, are highly dependent on their migratory potential from the peripheral non-lymphoid tissues to the lymph nodes, on the expression of adhesion molecules, which support the interaction of DC with T lymphocytes, and the cytokines secreted by DC, which polarize immune responses to Th1-mediated cellular or Th2-mediated antibody responses. These results altogether demonstrate that monocyte-derived DC are useful candidates for in vitro or in vivo targeting of antigens to induce efficient adaptive immune responses against pathogens and also against tumors.

New phenotypic, functional and electrophysiological characteristics of KG-1 cells

Myeloid dendritic cells (DC) are representatives of a rare and phenotypically diverse population of professional antigen presenting cells possessing high functional heterogeneity and flexibility. Here we studied the phenotypic, functional and electrophysiological characteristics of KG-1 cells, an erythroleukemia model cell line, which shares morphological and physiological similarities with immature and mature myeloid DC. We compared the expression of internalizing receptors and other cell surface molecules, antigen uptake and migration of unstimulated and activated KG-1 cells with the characteristics of immature and mature DC. Unstimulated KG-1 cells were less potent in capturing extracellular materials than immature DC. In contrast to monocyte-derived DC KG-1 cells stimulated by PMA and ionomycin ceased to migrate along the MIP-3beta chemokine gradient despite their high expression of CCR7 chemokine receptor and MDR, a transporter implicated in DC migration. Moreover, we determined the ion channel repertoire of KG-1 cells before and after treatment with PMA and ionomycin by using the patch-clamp technique. We found that both unstimulated and activated KG-1 cells expressed time- and voltage-independent, ChTx sensitive intracellular Ca(2+)-gated potassium conductance suggesting the presence of K(Ca) channels in their membranes. Based on our results we propose that KG-1 cells resemble myeloid DC but also possess unique phenotypic, functional and electrophysiological characteristics.