Interplay of polarity proteins and GTPases in T-lymphocyte function

Peripheral T cell lymphomas: from the bench to the clinic

Peripheral T cell lymphomas (PTCLs) are a heterogeneous group of orphan neoplasms. Despite the introduction of anthracycline-based chemotherapy protocols, with or without autologous haematopoietic transplantation and a plethora of new agents, the progression-free survival of patients with PTCLs needs to be improved. The rarity of these neoplasms, the limited knowledge of their driving defects and the lack of experimental models have impaired clinical successes. This scenario is now rapidly changing with the discovery of a spectrum of genomic defects that hijack essential signalling pathways and foster T cell transformation. This knowledge has led to new genomic-based stratifications, which are being used to establish objective diagnostic criteria, more effective risk assessment and target-based interventions. The integration of genomic and functional data has provided the basis for targeted therapies and immunological approaches that underlie individual tumour vulnerabilities. Fortunately, novel therapeutic strategies can now be rapidly tested in preclinical models and effectively translated to the clinic by means of well-designed clinical trials. We believe that by combining new targeted agents with immune regulators and chimeric antigen receptor-expressing natural killer and T cells, the overall survival of patients with PTCLs will dramatically increase.

Protein kinase C: a regulator of cytoskeleton remodelling and T-cell migration

Protein kinase C (PKC) is a family of ten serine/threonine kinases that have diverse roles in the signalling pathways regulating cellular proliferation, differentiation, apoptosis and immune responses. Elucidating roles for individual PKC isoforms in the immune responses of T-cells have long been a challenging prospect, because these cells are known to express nine of these isoforms. A variety of approaches including the use of knockout mice, overexpression of kinase-inactive mutants, cell-permeable peptides, pharmacological inhibitors and siRNAs have shown that PKCs regulate the production of inflammatory cytokines and the cytotoxic responses of various T-cell subsets. Central to the T-cell immune response is a requirement to migrate to various organs and tissues in search of pathogens and micro-organisms. T-cell migration is guided by specific sets of chemokines and integrin ligands that activate their cognate chemokine receptors and integrins on T-cells, resulting in remodelling of the cytoskeleton and the dynamic protrusive/contractile forces necessary for cell adhesion and motility. In the present article, we review the role of PKC in T-cell migration, with an emphasis on studies that have defined their roles in cytoskeletal remodelling, cell polarity and intracellular trafficking downstream of chemokine receptors and integrins.

Polarized cells, polarized views: asymmetric cell division in hematopoietic cells

It has long been recognized that alterations in cell shape and polarity play important roles in coordinating lymphocyte functions. In the last decade, a new aspect of lymphocyte polarity has attracted much attention, termed asymmetric cell division (ACD). ACD has previously been shown to dictate or influence many aspects of development in model organisms such as the worm and the fly, and to be disrupted in disease. Recent observations that ACD also occurs in lymphocytes led to exciting speculations that ACD might influence lymphocyte differentiation and function, and leukemia. Dissecting the role that ACD might play in these activities has not been straightforward, and the evidence to date for a functional role in lymphocyte fate determination has been controversial. In this review, we discuss the evidence to date for ACD in lymphocytes, and how it might influence lymphocyte fate. We also discuss current gaps in our knowledge, and suggest approaches to definitively test the physiological role of ACD in lymphocytes.

Divergent lymphocyte signalling revealed by a powerful new tool for analysis of time-lapse microscopy

We describe a new approach for interactive analysis of time-lapse microscopy, and apply this approach to elucidating whether polarity regulation is conserved between epithelial cells and lymphocytes. A key advantage of our analysis platform, 'TACTICS', is the capacity to visualize individual data points in the context of large data sets, similar to standard approaches in flow cytometry. Scatter plots representing microscopic parameters or their derivations such as polarity ratios are linked to the original data such that clicking on each dot enables a link to images and movies of the corresponding cell. Similar to flow cytometric analysis, subsets of the data can be gated and reanalyzed to explore the relationships between different parameters. TACTICS was used to dissect the regulation of polarization of the cell fate determinant, Numb, in migrating lymphocytes. We show here that residues of Numb that are phosphorylated by atypical protein kinase C (aPKC) to mediate apicobasal polarity in epithelial cells are not required for polarization of Numb in T cells, indicating that the role of aPKC is not conserved between lymphocytes and epithelia.

Clinical, immunological and molecular characterization of DOCK8 and DOCK8-like deficient patients: single center experience of twenty-five patients

PURPOSE

Autosomal recessive hyper-IgE syndrome is a rare combined immunodeficiency characterized by susceptibility to viral infections, atopic eczema, high serum IgE and defective T cell activation. The genetic etiologies are diverse. Null mutations in DOCK8 and TYK2 are responsible for many cases. This study aims to provide a detailed clinical and immunological characterization of the disease and explore the underlying genetic defects among a large series of patients followed by a single center. The available data might improve our understanding of the disease pathogenesis and prognosis.

METHODS

Clinical data of twenty-five patients diagnosed with AR-HIES were collected. Seventeen patients screened for STAT3, TYK2 and DOCK8 mutations.

RESULTS

Sinopulmonary infections, dermatitis, hepatic disorders, cutaneous and systemic bacterial, fungal and viral infections were the most common clinical features. The rate of hepatic disorders and systemic infections were high. Twelve patients died with a median age of 10 years. CMV infection was the only statistically significant predicting factor for poor prognosis (early death). Three novel DOCK8 mutations and two large deletions were found in thirteen patients. No mutations found in STAT3 or TYK2 genes.

CONCLUSION

Autosomal recessive hyper-IgE syndrome is a combined immunodeficiency disease characterized by high morbidity and mortality rate. The different genetic background and environmental factors may explain the more severe phenotypes seen in our series. DOCK8 defect is the most common identified genetic cause. Patients with no identified genetic etiology are likely to carry mutations in the regulatory elements of genes tested or in novel genes that are yet to be discovered.