Real-time measurements of membrane surface dynamics on macrophages and the phagocytosis of Leishmania parasites

Defocusing microscopy was used for real-time observation and quantification of membrane surface dynamics in murine bone marrow macrophages. Small random membrane fluctuations (SRMF), possibly metabolic driven, were detected uniformly over all membrane surface. Morphological and dynamical parameters of ruffles, such as shape, dimensions, and velocity of propagation, were analyzed. Optical tweezers were used to promote phagocytosis of single Leishmania amazonensis amastigotes by selected macrophages. Analysis of ruffling activity on the macrophages before and during phagocytosis of the parasites indicated that increased ruffling response near forming phagosomes, most likely induced by the parasite, accelerates phagocytosis. The effects of temperature decrease on the dynamics of membrane surface fluctuations and on the phagocytosis of parasites were used to determine the overall activation energies involved in these processes. The values obtained support the existence of strong correlation between membrane motility and phagocytic capacity.