Figure 3.

((a)–(c)) Light microscopy analysis of the interaction between A. griffini trophozoites and MDCK monolayers. (a) Control of MDCK epithelial cells monolayer incubated for 24 h in a mixture of equal proportions of Bacto Casitone and Dulbecco's modified Eagle's medium. Note the confluent appearance of the monolayer and the regular morphology of the epithelial cells. Bar = 2.0 μm. (b) After 24 h of coincubation between trophozoites and the epithelial cells, a noticeable damage is evident. Some areas of the substrate clearly lacking epithelial cells (asterisk) as well as remaining portions of the altered cell monolayer (Ec) are seen. Bar = 1.0 μm. (c) When MDCK monolayers were incubated with conditioned medium for 24 h rounded areas of varying size missing cells were seen. Bar = 2 μm. ((d),(e)) Thin sections of coincubations between amoebae and MDCK epithelial cells. (d) Trophozoites (T) were found in close contact with the surface of epithelial cells (Ec) and also under the cell layer. Epithelial cells appear undamaged; nevertheless an amoeba is initiating an injury process (white dotted circle) and is also engulfing cell debris (black dotted circle). Bar = 2 μm. (e) High magnification of the previous image where two phagocytic structures (Ps) start to engulf a portion of the epithelial cell. Bar = 2 μm.