As long-feeding ectoparasites, ixodid ticks have developed methods of altering host immune defenses in order to complete their blood meals. The immunomodulatory properties of tick vectors of Lyme disease and Rocky Mountain spotted fever have been studied extensively. Identification of the lone star tick Amblyomma americanum as a vector of the pathogen causing human monocytic ehrlichiosis has made it important to characterize the effects of this emerging vector on host immune systems. We have previously shown that lymphoid cells from BALB/c mice infested with A. americanum produce an altered cytokine profile, a reduced proliferative response, and decreased expression of helper T cell (CD4 +), cytotoxic T cell (CD8+), and memory cell (CD44+) surface markers. In this experiment we tested the hypothesis that the altered cytokine profile of infested mice is due to changes in numbers or phenotype of cytokine producing cells. We used cytometric quantification of fluorescent-antibody stained cells to compare intracellular production of IFN g, IL-2, IL-4, and IL-10 cytokines by CD4+ and CD8+ T cells from infested and control mice. We observed reductions in populations of both CD4+IL-2 + and CD8+ IL-2+ cells which coincided with suppression of IL-2 production by mitogen-stimulated cells taken from the same mice. Likewise, increases in populations of CD8+IL-4+ cells in infested mice coincided with significantly greater production of IL-4. Increases in IFN g+ and IL-10+ cells in infested mice were more striking among CD4-CD8- cells than in either CD4+ or CD8+ cells, implying that other cell types such as natural killer cells (producing IFN g) and macrophages (producing IL-10), are important sources of these cytokines during tick infestation. Our results suggest that A. americanum infestation can change the host’s production of these important disease-fighting cytokines by increasing or decreasing the number of cellular sources.
Species 1: Acari Ixodidae Amblyomma americanum (lone star tick)
Keywords: immunomodulation, vector
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA