CXCL12 is a costimulator for CD4+ T cell activation and proliferation in chronic lymphocytic leukemia patients

Activated T cells from patients with chronic lymphocytic leukemia (CLL) provide survival and proliferative signals to the leukemic clone within lymphoid tissues. Recruitment of both, CLL cells and T lymphocytes, to this supportive microenvironment greatly depends on CXCL12 production by stromal and myeloid cells. CXCL12 also supplies survival stimuli to leukemic B cells, but whether it exerts stimulatory effects on T lymphocytes from CLL patients is unknown. In order to evaluate the capacity of CXCL12 to increase CD4⁺ T cell activation and proliferation in CLL patients, peripheral blood mononuclear cells were cultured with or without recombinant human CXCL12 or autologous nurse-like cells, and then T cell activation was induced by anti-CD3 mAb. CXCL12 increases the proliferation and the expression of CD25, CD69, CD154, and IFNγ on CD3-stimulated CD4⁺ T cells from CLL patients, similarly in T cells from ZAP-70⁺ to ZAP-70^? patients. Autologous nurse-like cells establish a close contact with CD4⁺ T cells and increase their activation and proliferation partially through a CXCR4-dependent mechanism. In addition, we found that activated T cells in the presence of CXCL12 enhance the activation and proliferation of the leukemic clone. In conclusion, CXCL12 production by lymphoid tissue microenvironment in CLL patients might play a key dual role on T cell physiology, functioning not only as a chemoattractant but also as a costimulatory factor for activated T cells.     

Isolation and sequence determination of an active site peptide of rabbit muscle pyruvate kinase

Rabbit muscle pyruvate kinase was inactivated by 2', 3'-dialdehyde ADP with the incorporation of one molecule of reagent per enzyme subunit. The inactivated protein was digested with trypsin after reduction and carboxymethylation. The labeled peptide was isolated by gel filtration and further purified by HPLC. The peptide was sequenced both by liquid-phase and gas-phase automatic Edman degradation. A 34-residue peptide was obtained. This peptide is identical to a tryptic peptide labeled with trinitrobenzenesulfonate, isolated and sequenced by Johnson et al. (Biochem. Biophys. Res. Commun. (1979) 90, 525-530) from bovine muscle pyruvate kinase. Available evidence suggests that dialdehyde ADP labels the enzyme at the same lysine in position 25 of the peptide, as found by Johnson et al. The high homology between the isolated peptide and regions of other pyruvate kinases from low to high eukaryotes supports the idea that this peptide is related to the enzyme active site.     

Macromolecular structure of the organic framework of nacre in Haliotis rufescens: implications for growth and mechanical behavior

We have performed a macromolecular structural analysis of the interlamellar and intertabular parts of the organic framework of the nacreous part of the shell of Haliotis rufescens, including the identification of structural chitin. Using histochemical optical microscopy we have mapped the locations of carboxylates and sulfates of proteins and chitin on the surfaces and within the core of the interlamellar layers and the intertabular matrix that together form the external organic matrix of composite nacre. This extends the earlier work of Nudelmann et al. [Nudelman, F., Gotliv, B.A., Addadi, L. and Weiner, S. 2006. Mollusk shell formation: mapping the distribution of organic matrix components underlying a single aragonite tablet in nacre. J. Struct. Biol. 153, 176–187] and Crenshaw and Ristedt [Crenshaw, M.A., Ristedt, H. 1976. The histochemical localization of reactive groups in septal nacre from Nautilus pompilius. In: Omori, M., Watabe, N. (Eds.) The Mechanisms of Biomineralization in Animals and Plants. Tokai University Press, Toyko] on Nautilus pompilius. Our mapping identifies distinct regions, defined by the macromolecular groups, including what is proposed to be the sites of CaCO₃ nucleation and that play a key role in nacre growth. Using AFM scanning probe microscopy we have identified a fibrous core within the framework that we associate with chitin. The structural picture that is evolved is then used to develop a simple structural model for the organic framework which is shown to be consistent with mechanical property measurements. The role of the intracrystalline matrix within the nacre tablets in mediating nacre’s mechanical response is noted within the framework of our model.     

The Role of Propagating and Localized Surface Plasmons for SERS Enhancement in Periodic Nanostructures

Periodic arrays of plasmonic nanopillars have been shown to provide large, uniform surface-enhanced Raman scattering (SERS) enhancements. We show that these enhancements are the result of the combined impact of localized and propagating surface plasmon modes within the plasmonic architecture. Here, arrays of periodically arranged silicon nanopillars of varying sizes and interpillar gaps were fabricated to enable the exploration of the SERS response from two different structures; one featuring only localized surface plasmon (LSP) modes and the other featuring LSP and propagating (PSP) modes. It is shown that the LSP modes determine the optimal architecture, and thereby determine the optimum diameter for the structures at a given incident. However, the increase in the SERS enhancement factor for a system in which LSP and PSP cooperatively interact was measured to be over an order of magnitude higher and the peak in the diameter dependence was significantly broadened, thus, such structures not only provide larger enhancement factors but are also more forgiving of lithographic variations.     

Chronic lymphocytic leukemia cells bind and present the erythrocyte protein band 3: possible role as initiators of autoimmune hemolytic anemia

The mechanisms underlying the frequent association between chronic lymphocytic leukemia (CLL) and autoimmune hemolytic anemia are currently unclear. The erythrocyte protein band 3 (B3) is one of the most frequently targeted Ags in autoimmune hemolytic anemia. In this study, we show that CLL cells specifically recognize B3 through a still unidentified receptor. B3 interaction with CLL cells involves the recognition of its N-terminal domain and leads to its internalization. Interestingly, when binding of erythrocyte-derived vesicles as found physiologically in blood was assessed, we observed that CLL cells could only interact with inside-out vesicles, being this interaction strongly dependent on the recognition of the N-terminal portion of B3. We then examined T cell responses to B3 using circulating CLL cells as APCs. Resting B3-pulsed CLL cells were unable to induce T cell proliferation. However, when deficient costimulation was overcome by CD40 engagement, B3-pulsed CLL cells were capable of activating CD4(+) T cells in a HLA-DR-dependent fashion. Therefore, our work shows that CLL cells can specifically bind, capture, and present B3 to T cells when in an activated state, an ability that could allow the neoplastic clone to trigger the autoaggressive process against erythrocytes.