Performance of bat-derived macrophages at different temperatures

Heterothermy, as a temperature-dependent physiological continuum, may affect host-pathogen interactions through modulation of immune responses. Here, we evaluated proliferation and functional performance of a macrophage cell line established from the greater mouse-eared (Myotis myotis) bat at 8, 17.5, and 37 degrees C to simulate body temperatures during hibernation, daily torpor and euthermia. Macrophages were also frozen to -20 degrees C and then examined for their ability to proliferate in the immediate post-thaw period. We show that bat macrophages can proliferate at lower temperatures, though their growth rate is significantly slower than at 37 degrees C. The cells differed in their shape, size and ability to attach to the plate surface at both lower temperatures, being spheroidal and free in suspension at 8 degrees C and epithelial-like, spindle-shaped and/or spheroidal at 17.5 degrees C. While phagocytosis at temperatures of 8 and 17.5 degrees C amounted to 85.8 and 83.1% of the activity observed at 37 degrees C, respectively, full phagocytic activity was restored within minutes of translocation into a higher temperature. Bat-derived macrophages were also able to withstand temperatures of -20 degrees C in a cryoprotectant-free cultivation medium and, in the immediate post-thaw period, became viable and were able to proliferate. Our in vitro data enhance understanding of macrophage biology.