neoformans for an additional 1 hr and subsequent microscopic imaging. Collection of human peripheral blood monocytes and phagocytosis Monocytes were isolated
by Ficoll-Hypaque (GE Healthcare, Piscataway, NJ) density gradient centrifugation as described previously . Briefly, diluted venous blood from one healthy donor was diluted with Hank’s balanced salt solution (Mediatech, Herndon, Va) and was layered on top of Ficoll-Hypaque (GE Healthcare) at a 1:1 ratio and centrifuged at 2000 rpm/4°C for 15 minutes without brake. The monocyte layer was removed and red blood cells were lysed using lysing buffer (0.155 M NH4Cl pH 7.4). Cells were washed three times with Hank’s balanced salt solution and suspended in RPMI (Mediatech) media supplemented with 10% fetal calf serum (Gemini Bioproducts, West Sacramento, Ca) and cells were then plated on poly-lysine coverslip-bottom PS-341 in vivo MaTtek plates (Ashland, MA)
at a density of 2 × 105 per well in feeding media and allowed to adhere at 37°C and 10% CO2 for 6 days prior to incubation with C. neoformans, using 18B7 (10 ug/ml) or 20% human serum, for 1 hr and subsequent microscopic imaging. This study was done with the approval of our institutional review board committee at the Albert Einstein College of Medicine and prior consent was obtained from blood donors. Time-lapse imaging For live cell imaging, phagocytosis assays were done as described . Briefly, 105 HPBM were plated on polylysine FG-4592 coated coverslip bottom MatTek plates and allowed to adhere for 6 days. The media was then removed and replaced with fresh media containing C. neoformans cells (C. Aldol condensation neoformans to HPBM ratio of 10:1) along with monoclonal antibody (mAb) against the cryptococcal capsule (mAb 18B7, 50 μg/ml). C. neoformans
were opsonized with either mAb 18B7 or 20% guinea pig serum as indicated above. HPBMs and C. neoformans were then incubated together for 30 min at 4°C to synchronize phagocytosis, followed by 60 min incubation at 37°C to allow for completion of phagocytosis. This was followed by two washes with fresh media (1 ml each), and replenishment with 2 ml feeding media. The plates were then taken for time-lapse imaging every 4 minutes using an Axiovert 200 M inverted microscope and photographed with an AxiocamMR camera controlled by the Axio Vision 4.4 software (Carl Zeiss Micro Imaging, NY). This microscope was housed in a Plexiglas box and the temperature was stabilized at 37°C with a forced air heater system. The plate lid was kept in place to prevent evaporation, and 5% CO2 was delivered to a chamber locally at the culture dish. Quantitative analysis of phagosomal extrusion and cell to cell spread was carried out by compiling all the movies and counting the number of macrophages with internalized C.