Targeting of an activated T-cell subset using a bispecific antibody- toxin conjugate directed against CD4 and CD26

We have developed a bispecific antibody that recognizes the CD4 and CD26 antigens simultaneously and that was examined for its ability to target CD4+CD26+T cells. These latter cells constitute the activated component of the CD4+ CD29highCD45RO+ memory T-cell subset that provides help for B-cell Ig synthesis and help for responses against recall antigens. The purified bispecific antibody exhibited an estimated dissociation constant (kd) of 2.4 x 10(-9) mol/L, on comparison with 1.1 x 10(-9) mol/L for anti-CD26, and 1.6 x 10(-10) mol/L for anti-CD4. Surface plasmon resonance was used to show the bifunctional capacity of the antibody. On binding 125I-bispecific antibody to phytohemagglutinin (PHA)-activated T cells, 54.4% of the bound antibody was internalized. This was the result of bispecific binding, because monovalent fragments of anti-CD4 and anti-CD26 were not able to modulate antigen or induce internalization using both a fluorescent assay and an 125I-internalization assay. The ability of the bispecific antibody to be internalized was used to deliver a toxin, blocked ricin, specifically to cells that are CD4+CD26+. The inability of monovalent fragments to be internalized formed the basis for our hypothesis that monovalent binding by the bispecific immunotoxin would not result in internalization. Against resting E+ T cells, the bispecific immunotoxin developed a minimal effect. On preactivating the same cells, using phorbol myristate acetate (PMA)/ionomycin on concanavalin A (ConA) or especially PHA, levels of CD26 were upregulated and the immunotoxin effectively inhibited the ability to provide help for B-cell Ig synthesis while leaving intact the CD4-CD26+ and CD4+CD26- populations; an effect observed both functionally and by phenotype. The bispecific antibody proved to be most effective at inhibiting a heterologous mixed leukocyte reaction. We propose that this reagent may form the basis for the rational design of toxins designed to modulate activated T cells from, or directed against, tissue grafts.     

Bilateral subacromial bursitis with macroscopic rice bodies: Ultrasound,CT and MR appearance

The radiological findings of ultrasound, CT and MR of a case of bilateral subacromial bursitis with macroscopic rice bodies is described. The previous literature is also reviewed.     

Selective Interaction of a Cationic Polyfluorene with Model Lipid Membranes: Anionic versus Zwitterionic Lipids

This paper explores the interaction mechanism between the conjugated polyelectrolyte {[9,9-bis(6’-N,N,N-trimethylammonium)hexyl]fluorene-phenylene}bromide (HTMA-PFP) and model lipid membranes. The study was carried out using different biophysical techniques, mainly fluorescence spectroscopy and microscopy. Results show that despite the preferential interaction of HTMA-PFP with anionic lipids, HTMA-PFP shows affinity for zwitterionic lipids; although the interaction mechanism is different as well as HTMA-PFP’s final membrane location. Whilst the polyelectrolyte is embedded within the lipid bilayer in the anionic membrane, it remains close to the surface, forming aggregates that are sensitive to the physical state of the lipid bilayer in the zwitterionic system. The different interaction mechanism is reflected in the polyelectrolyte fluorescence spectrum, since the maximum shifts to longer wavelengths in the zwitterionic system. The intrinsic fluorescence of HTMA-PFP was used to visualize the interaction between polymer and vesicles via fluorescence microscopy, thanks to its high quantum yield and photostability. This technique allows the selectivity of the polyelectrolyte and higher affinity for anionic membranes to be observed. The results confirmed the appropriateness of using HTMA-PFP as a membrane fluorescent marker and suggest that, given its different behaviour towards anionic and zwitterionic membranes, HTMA-PFP could be used for selective recognition and imaging of bacteria over mammalian cells.