Cells in pulmonary blood vessels. A: RBCs, pRBCs, macrophages (mac), PMNs, and platelets (plt) within alveolar capillaries were counted by transmission electron microscopy. Results are the mean (±SD, n = 5), of the ratio with RBCs seen in individual mice. Macrophage and PMN sequestration was significantly (P < 0.05) increased in infected +/+, compared to noninfected +/+ mice, whereas macrophage and PMN sequestration was also significantly less important in infected CD40−/−, compared to +/+ mice. B: pRBCs in large blood vessels and alveolar capillaries were counted in large blood vessels and in the alveolar capillaries observed on thin sections by transmission electron microscopy. The results are the mean (±SD, n = 5) of the percentage of pRBCs.