Human Peripheral Blood Mononuclear Cells Exhibit Heterogeneous CD52 Expression Levels and Show Differential Sensitivity to Alemtuzumab Mediated Cytolysis

Alemtuzumab is a monoclonal antibody that targets cell surface CD52 and is effective in depleting lymphocytes by cytolytic effects in vivo. Although the cytolytic effects of alemtuzumab are dependent on the density of CD52 antigen on cells, there is scant information regarding the expression levels of CD52 on different cell types. In this study, CD52 expression was assessed on phenotypically distinct subsets of lymphoid and myeloid cells in peripheral blood mononuclear cells (PBMCs) from normal donors. Results demonstrate that subsets of PBMCs express differing levels of CD52. Quantitative analysis showed that memory B cells and myeloid dendritic cells (mDCs) display the highest number while natural killer (NK) cells, plasmacytoid dendritic cells (pDCs) and basophils have the lowest number of CD52 molecules per cell amongst lymphoid and myeloid cell populations respectively. Results of complement dependent cytolysis (CDC) studies indicated that alemtuzumab mediated profound cytolytic effects on B and T cells with minimal effect on NK cells, basophils and pDCs, correlating with the density of CD52 on these cells. Interestingly, despite high CD52 levels, mDCs and monocytes were less susceptible to alemtuzumab-mediated CDC indicating that antigen density alone does not define susceptibility. Additional studies indicated that higher expression levels of complement inhibitory proteins (CIPs) on these cells partially contributes to their resistance to alemtuzumab mediated CDC. These results indicate that alemtuzumab is most effective in depleting cells of the adaptive immune system while leaving innate immune cells relatively intact

Magnetizable duplex steel stents enable endothelial cell capture

Emerging medical nanotechnology applications often utilize magnetic forces to guide the movement of superparamagnetic particle linked cells and drugs in order to achieve a therapeutic effect. Superparamagnetic particle labeled endothelial cells have previously been captured on the surface of prototype nickel-plated stents in proof of concept studies. Facilitated endothelialization may help improve the healing of stented arteries and reduce the risk of stent thrombosis and restenosis. Extensive evaluation of candidate materials led to the development of a magnetizable 2205 duplex stainless steel stent. Magnetic field strengths of approximately 630 mG were induced within these stents by holding them in close proximity to a 0.7 T rare earth magnet. The magnetic field strength was reliably maintained over several days, but was partially reduced upon mild mechanical shock or plastic deformation. Mechanical testing demonstrated that stents could withstand crimping and expansion necessary for vascular implantation; however, magnetic field strength was significantly reduced. When placed in an endothelial cell suspension of 1×106 cells/mL, magnetized stents captured approximately 310 cells/mm2 compared to approximately 35 cells/mm2 for non-magnetized control stents. These data provide quantitative support to the observation that low level magnetization of stents may be adequate to attract labeled, autologous, blood-derived endothelial outgrowth cells following stent placement. This, in turn, may lead to more rapid and complete healing of stented arteries with a concomitant improvement in stent performance