CD20 positive childhood B-non Hodgkin lymphoma (B-NHL): morphology, immunophenotype and a novel treatment approach: a single center experience.

Lymphomas represent the third most common group of cancers in childhood and adolescence, mature B non Hodgkin's lymphoma (B-NHL) accounting for up to 60% of newly diagnosed patients. The diagnosis of specific entities of B-NHL is based on well-defined morphologic analysis, immunophenotyping, cytogenetics and molecular genetics, which determine the optimal treatment strategy. In adult population a major turning point in treatment of B-NHL has been achieved since rituximab, in combination with CHOP has improved the survival rate up to 19%. Rituximab is a chimeric monoclonal antibody that targets CD20, a transmembrane calcium channel expressed on normal and malignant B-cells that mediates cytotoxic, apoptotic and anti-proliferative effects. The effect of rituximab in pediatric population is still not well enough investigated. Based on morphology and immunophenotype of malignant cells, seven children with B-NHL in our institution were eligible for treatment with modified B-NHL-Berlin-Frankfurt-Münster (BFM)-95-based protocol with rituximab administered on day -5. The complete remission was achieved in all seven patients. Six patients are still in complete remission at least 12 months after having finished chemotherapy and one patient relapsed two months after the last cycle and subsequently died. Major adverse effects observed during treatment were prolonged B-cell depletion and myelosuppression. Rituximab in combination with B-NHL-BFM-95 protocol was otherwise well tolerated and proved to be effective in children and adolescents with B-NHL. The number of our patients is too small and the follow-up of a larger group of patients will help in defining the role of rituximab in the treatment of childhood B-NHL.

Heterogeneity of glycinergic and gabaergic interneurons in the granule cell layer of mouse cerebellum.

Interneurons of the cerebellum granule cell layer (GCL) form distinct populations. Golgi cells extend dendrites in the molecular layer (ML) and innervate granule cells. In contrast, Lugaro cells have dendrites confined to the GCL but innervate interneurons in the ML, and globular cells have both their dendrites and axons in the ML. The latter cells were described recently and remain poorly characterized. Although several neurochemical markers have been associated selectively with GCL interneurons, it is unclear how they relate to their morphological classification and neurochemical phenotype (glycinergic and/or gamma-aminobutyric acid [GABA]ergic). Here, we performed a detailed characterization of GCL interneurons in mice expressing enhanced green fluorescent protein (GFP) in glycinergic and GABAergic neurons, respectively. By using immunofluorescence for metabotropic glutamate receptor 2 (mGluR2) and neurogranin as markers, we demonstrate the existence of five non-overlapping subsets of Golgi cells: about 65% are glycinergic/GABAergic and co-express both markers. Two small subsets (5-10%) also contain both neurotransmitters but express only mGluR2; they are distinguished by cell body size and location in the GCL. The fourth subset (15%) is GABAergic only and expresses neurogranin. The fifth subset (5%) is glycinergic only and lacks both markers. Thus, the heterogeneity of Golgi cells suggests that they belong to specific functional circuits and are differentially regulated by mGluRs and Ca(2+)-calmodulin-dependent signaling pathways. In contrast to Golgi cells, Lugaro and globular cells are glycinergic/GABAergic and lack mGluR2 and neurogranin. They each represent at least 15% of GCL interneurons and extensively innervate stellate and basket cells, but not Purkinje cells, emphasizing their contribution to inhibitory control of ML interneurons.

GABAergic synaptogenesis marks the onset of differentiation of basket and stellate cells in mouse cerebellum.

Type 2 glycine transporter (GlyT2) mediates intracellular glycine transport and is expressed selectively in glycinergic neurons. Expression of GlyT2 gene promoter-driven enhanced green fluorescent protein (eGFP) in BAC transgenic mice allows selective visualization of glycinergic neurons by fluorescence microscopy. Here, we show that cerebellar interneuron precursors identified by the transcription factor Pax2, including gamma-aminobutyric acid (GABA)ergic interneurons of the molecular layer (ML; basket and stellate cells), transiently express GlyT2-eGFP during development. In contrast, expression of endogenous GlyT2 is restricted to glycinergic Golgi cells. Comparison with knock-in mice expressing eGFP in GABAergic neurons [glutamic acid decarboxylase (GAD)67-eGFP] revealed that GlyT2-eGFP expression often precedes GAD67-eGFP and is therefore a marker of immature GABAergic interneurons. In the internal granule cell layer, GABAergic Golgi cells differentiated shortly after birth, prior to glycinergic Golgi cells. In the ML, GlyT2-eGFP-positive precursor cells migrated until the boundary with the external granule cell layer, forming an inside-out maturation gradient that determined the final position of interneurons in the ML. After migration, GlyT2-eGFP gradually disappeared, while interneurons differentiated morphologically and became immunoreactive for parvalbumin, the GABA(A) receptor alpha1 subunit, and the K(+)Cl(-) exchanger KCC2 (K(+)Cl(-) cotransporter type 2). Numerous presumptive GABAergic synaptic terminals were seen on immature ML interneurons as early as P4, preceding the expression of these neurochemical markers. These results suggest that GABAergic synaptogenesis marks the onset of differentiation of basket and stellate cells in the mouse cerebellum, and that GABAergic synaptic function might contribute to the differentiation of interneurons in the cerebellar cortex.