Fig. 7: monocyte cells of adult opossum were treated with trypsin, following fixation and incubation with cationized ferritin (large arrow). No reaction was observed at the surface of the cells (49.000 X). Fig. 8: treatment of the monocytes cells with neuraminidase. After fixation and incubation with cationized ferritin (CF), cells showed an irregular distribution at the surface with some regions of the plasma membrane presenting the electrondense marker (arrowhead) and others completely devoid of CF (thin arrows) (22.000 X).