FIG. 1.

Expression levels of large nonlymphocytes of CD11b and MHC class II from alveolar spaces of Pneumocystis-infected animals were very low at day 10 postinfection in neonatal mice compared to those for adult mice. Mice were infected with Pneumocystis as neonates (24 to 72 h after birth) or adults, and lungs were lavaged at day 10 postinfection to examine macrophage levels. Cells were stained with antibodies specific for CD11c and CD11b or MHC class II, and phenotypes were examined by using flow cytometry. Representative histograms of CD11b-positive cells (gated on CD11c⁺ cells) and MHC class II-positive cells (gated on large nonlymphocytes) are shown. Cells were gated for large nonlymphoid cells by using forward and side light scatter. Controls included BALF cells from uninfected neonates or adults. Data are representative of results for three to five mice per group.