ABSTRACT
The desire for designing efficient synthetic methods that lead to industrially important nanomaterials has led a desire to more fully understand the mechanism of growth and how modern synthetic techniques can be employed. Microwave (MW) synthesis is one such technique that has attracted attention as a green, sustainable method. The reports of enhancement of formation rates and improved quality for MW driven reactions are intriguing, but the lack of understanding of the reaction mechanism and how coupling to the MW field leads to these observations is concerning. In this manuscript, the growth of a metal nanoparticles (NPs) in a microwave cavity is spectroscopically analyzed and compared with the classical autocatalytic method of NP growth to elucidate the underpinnings for the observed enhanced growth behavior for metal NPs prepared in a MW field. The study illustrates that microwave synthesis of nickel and gold NPs below saturation conditions follows the Finke-Watzky mechanism of nucleation and growth. The enhancement of the reaction arises from the size-dependent increase in MW absorption cross section for the metal NPs. For Ni, the presence of oxides is considered via theoretical computations and compared to dielectric measurements of isolated nickel NPs. The study definitively shows that MW growth can be modeled by an autocatalytic mechanism that directly leads to the observed enhanced rates and improved quality widely reported in the nanomaterial community when MW irradiation is employed.
ABSTRACT
Although there are many examples (eg, immune deviation) in which enhanced cellular responses correspond with lower humoral responses, here we demonstrate for the first time 2 models in which cytotoxic T-lymphocyte (CTL) activity is associated with an enhanced antibody response. First, C57BL/6 mice generate a stronger antibody response to ovalbumin DNA immunization than congenic bm1 mice. The latter differ from C57BL/6 mice in that the H-2Kb molecule is mutated so that the immunodominant CTL epitope of ovalbumin is no longer presented. Second, pre-existing CTLs (induced by ovalbumin peptide-priming) increased the antibody response to a second unrelated antigen (beta-galactosidase) co-immunized with ovalbumin. One possible mechanism is that CTLs may release antigen from DNA-transfected cells by killing or damaging them, and this freed antigen is then accessible to dendritic cells and B cells. Our finding of CTL-mediated antibody enhancement has important implications for tumor and viral immunobiology and vaccination.
Subject(s)
T-Lymphocytes, Cytotoxic/immunology , Vaccines, DNA/pharmacology , Animals , Antibody Formation , Cytotoxicity, Immunologic , Epitopes , Immunization , Mice , Mice, Congenic , Mice, Inbred C57BL , Mice, Knockout , Models, Immunological , Ovalbumin/genetics , Ovalbumin/immunology , Vaccines, DNA/geneticsABSTRACT
The localisation of antigen within secondary lymphoid organs can significantly increase the immune response. Using the monoclonal antibody M/K 2.7, which recognises murine vascular cell adhesion molecule (VCAM), we have shown antigen accumulation within organs of the secondary lymph such as the draining lymph nodes and spleen. Similar accumulation was not apparent in other, non-lymphatic organs. We then compared the immune response to antigen targeted to secondary lymphoid organs, via VCAM recognition, with untargeted antigen. The model antigen used, rat IgG1, was shown to be a weak murine immunogen, not eliciting any measurable antibody or cellular response. However, the same antigen targeted to VCAM, was shown to elicit an IgG1 antibody response and T cell proliferation, also marked by IFNgamma expression. These results confirm the effectiveness of targeting antigen to secondary lymphoid organs in enhancing an immune response and identify VCAM as a useful target.
