Figure 2.

Determination of pH_p in wild-type and Nramp1 ^−/− macrophages. Phagosomal pH was measured by ratio imaging as described for Fig. 1 (see Materials and Methods) in peritoneal macrophages obtained from wild-type (Nramp ^+/+) mice and Nramp1 mutant mice (Nramp1 ^−/−). Phagosome formation was induced using either live, fluoresceinated M. bovis (A, B, and leftmost bar in C), dead M. bovis (middle bar in C), or opsonized latex beads (rightmost bar in C). (A) frequency histogram comparing the pH in wild-type (Nramp ^+/+) mice and Nramp1 mutant mice (Nramp1 ^−/−); (B) summary of results comparing Nramp ^+/+ and Nramp1 ^−/− cells; data are means ± SE of 37 individual determinations; (C) summary of results comparing different phagocytic particles in Nramp1 ^−/− cells. Data are means ± SE of 24 determinations.