Human regulatory T cells lack the cyclophosphamide‐extruding transporter ABCB1 and are more susceptible to cyclophosphamide‐induced apoptosis

ATP‐binding cassette (ABC) transporters, including ABC‐transporter B1 (ABCB1), extrude drugs, metabolites, and other compounds (such as mitotracker green (MTG)) from cells. Susceptibility of CD4⁺ regulatory T (Treg) cells to the ABCB1‐substrate cyclophosphamide (CPA) has been reported. Here, we characterized ABCB1 expression and function in human CD4⁺ T‐cell subsets. Naïve, central memory, and effector‐memory CD4⁺ T cells, but not Treg cells, effluxed MTG in an ABCB1‐dependent manner. In line with this, ABCB1 mRNA and protein was expressed by nonregulatory CD4⁺ T‐cell subsets, but not Treg cells. In vitro, the ABCB1‐substrate CPA was cytotoxic for Treg cells at a 100‐fold lower dose than for nonregulatory counterparts, and, inversely, verapamil, an inhibitor of ABC transporters, increased CPA‐toxicity in nonregulatory CD4⁺ T cells but not Treg cells. Thus, Treg cells lack expression of ABCB1, rendering them selectively susceptible to CPA. Our findings provide mechanistic support for therapeutic strategies using CPA to boost anti‐tumor immunity by selectively depleting Treg cells.     

Monoclonal antibody F1 binds to the kringle domain of factor XII and induces enhanced susceptibility for cleavage by kallikrein

In a previous study we have shown that monoclonal antibody F1 (MoAb F1), directed against an epitope on the heavy chain of factor XII distinct from the binding site for anionic surfaces, is able to activate factor XII in plasma (Nuijens JH, et al: J Biol Chem 264; 12941, 1989). Here, we studied in detail the mechanism underlying the activation of factor XII by MoAb F1 using purified proteins. Formation of factor XIIa was assessed by measuring its amidolytic activity towards the chromogenic substrate H-D-Pro-Phe-Arg-pNA (S-2302) in the presence of soybean trypsin inhibitor and by assessing cleavage on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Upon incubation with MoAb F1 alone, factor XII was auto-activated in a time-dependent fashion, activation being maximal after 30 hours. Factor XII incubated in the absence of MoAb F1 was hardly activated by kallikrein, whereas in the presence of MoAb F1, but not in that of a control MoAb, the rate of factor XII activation by kallikrein was promoted at least 60-fold. Maximal activation of factor XII with kallikrein in the presence of MoAb F1 was reached within 1 hour. This effect of kallikrein on the cleavage of factor XII bound to MoAb F1 was specific because the fibrinolytic enzymes plasmin, urokinase, and tissue-type plasminogen activator could not substitute for kallikrein. Also, trypsin could easily activate factor XII, but in contrast to kallikrein, this activation was independent of MoAb F1. SDS-PAGE analysis showed that the appearance of amidolytic activity correlated well with cleavage of factor XII. MoAb F1-induced activation of factor XII in this purified system was not dependent on the presence of high- molecular-weight kininogen (HK), in contrast to the activation of the contact system in plasma by MoAb F1. Experiments with deletion mutants revealed that the epitopic region for MoAb F1 on factor XII is located on the kringle domain. Thus, this study shows that binding of ligands to the kringle domain, which does not contribute to the proposed binding site for negatively charged surfaces, may induce activation of factor XII. Therefore, these findings point to the existence of multiple mechanisms of activation of factor XII.     

Recurrences of supratentorial meningiomas. Apropos of 17 cases

17 cases of recurrent meningiomas observed during a 10 years period are reviewed. Meningiomas with a second localisation different from the first were excluded from the study. The tumor recurrence occurred mostly during the first five years after the surgical procedure. One case with femoral and pulmonary metastasis is described. Several factors may play a role in the genesis of the recurrence: age, sex, the tumor localisation, CT scan, the importance of the tumor ablation, the histology. In almost all cases a radiotherapy was carried out after the second surgical procedure. This retrospective study suggests the need for multifactorial prospective analysis with clinical, paraclinical and fundamental factors. Such a study would be useful to precise the natural history of meningiomas.     

Multidisciplinary care: periodontal aspects to treatment planning the anterior esthetic zone

The field of periodontology has changed dramatically during the past 30 years. The goal of periodontal therapy is not only to establish and maintain the dentition and the periodontium free of any oral infections, but also to provide an environment with optimal function and esthetics. Esthetics has become an integral portion of the overall treatment goal in periodontics. This article discusses the role of periodontal plastic and reconstructive surgery in treatment planning the anterior esthetic zone in interdisciplinary dental care.     

Multiple metastases during the course of a pineal germinoma

The clinical findings and course of a patient with a germinoma of the pineal region is presented. After a surgical procedure and radiation treatment, ten months after, the patient develops successively peritoneal, ventricular, spinal metastasis. Effective treatment was either radiation treatment or chemotherapy. The frequency of metastasis with germinomas of the posterior part of the third ventricle are discussed, following a review of the literature, prevention and treatment are discussed.     

Crown lengthening surgery: a restorative-driven periodontal procedure.

Improper management of the periodontal tissues during restorative procedures is a common, but often overlooked, cause of failure. When a restoration is placed, the preservation of an intact, healthy periodontium is necessary to maintain the tooth or teeth being restored. Predictable long-term restorative success requires a combination of restorative principles with the correct management of the periodontal tissues.