Structure of polydisperse inverse ferrofluids: theory and computer simulation.

By using theoretical analysis and molecular dynamics simulations, we investigate the structure of colloidal crystals formed by nonmagnetic microparticles (or magnetic holes) suspended in ferrofluids (called inverse ferrofluids), by taking into account the effect of polydispersity in size of the nonmagnetic microparticles. Such polydispersity often exists in real situations. We obtain an analytical expression for the interaction energy of monodisperse, bidisperse, and polydisperse inverse ferrofluids. Body-centered tetragonal (bct) lattices are shown to possess the lowest energy when compared with other sorts of lattices and thus serve as the ground state of the systems. Also, the effect of microparticle size distributions (namely, polydispersity in size) plays an important role in the formation of various kinds of structural configurations. Thus, it seems possible to fabricate colloidal crystals by choosing appropriate polydispersity in size.

Brucella abortus induces a novel cytokine gene expression pattern characterized by elevated IL-10 and IFN-gamma in CD4+ T cells.

Immunization of BALB/c mice with killed Brucella abortus (BA) has previously been shown to increase serum IgG2a levels and long-term T cell clones from these mice secrete Th1-associated cytokines: IFN-gamma and IL-2 but not IL-4 or IL-5. We analyzed cytokine gene expression following primary immunization with BA to determine when CD4+ T cells first express cytokine genes and whether specific hypothesized cytokine patterns (e.g. Th precursor, Th0) could be identified prior to a Th1-like pattern. Our results demonstrated a highly consistent and novel pattern of Th1/Th2 cytokine gene expression characterized by elevated IL-10 and IFN-gamma in CD4+ T cells which rapidly manifests itself and is sustained for at least 10 days after immunization. No elevation in IL-2 cytokine gene expression was observed and treatment of BA-immunized mice with blocking anti-IL-2 antibodies had no effect on the cytokine gene expression pattern, although treatment with anti-IFN antibodies resulted in increased IL-4, IL-5, and IL-9 cytokine gene expression, in the absence of any change in IFN-gamma or IL-10 as early as 4 days after immunization. These results suggest that a whole pathogen may trigger sufficient costimulatory signals to rapidly induce effector T cells in the absence of elevated IL-2 and that IL-10 is specifically elevated in certain Th1-like responses.

Cytokine gene expression after in vivo primary immunization with goat antibody to mouse IgD antibody.

Cytokines are important mediators of effector lymphoid cell function during an immune response, but their expression during an in vivo immune response has not been well documented. We analyzed the kinetics of cytokine gene expression during the course of an in vivo primary immune response to goat antibody to mouse IgD antibody. Total RNA was purified from spleens taken from freshly killed BALB/c mice 1 to 7 days after immunization. The reverse transcriptase polymerase chain reaction was used to evaluate the expression of seven cytokine genes, all of which encode cytokines that are secreted by T cells and are important in T and/or B cell activation and differentiation. These were IFN-gamma, IL-2, IL-4, IL-5, IL-6, IL-9, and IL-10. IL-2 and IL-9 exhibited an early elevated expression at days 2 to 3, and declined as the expression of IL-4, IL-6, IL-10, and IFN-gamma increased. In contrast, IL-5 gene expression showed little change, exhibiting a similar pattern to the housekeeping gene, hypoxanthine-guanine phosphoribosyl transferase. Cell sorting of CD4+ and CD4- cells at day 3 and day 5 after immunization revealed that CD4+ cells were the predominant source of the elevated cytokines (with the exception of IL-6). Our results demonstrate a specific and highly reproducible cytokine gene expression pattern during the course of a primary in vivo immune response that is marked by an absence of a clear-cut Th1/Th2 dichotomy.