Differential leukocyte analysis of blood and spleen populations measured over time in infected animals. Cell counts were made on blood (left-hand panels) or spleen (right-hand panels) leukocytes from the time course experiment (see Fig 3). Cells from +/+ mice are shown in the top panels, while −/− cells are in the bottom panels. Time after infection is shown in the abscissa. Blood differential counts: open bars, lymphocytes; closed bars, neutrophils and band forms (note that few band forms were observed in +/+ mice while the number was high in −/− mice); striped bars, monocytes. Spleen differential counts: open bars, lymphocytes; diagonally striped bars, blast forms; closed bars, band forms; vertically striped bars, mature (fully segmented nucleus) neutrophils; grey bars, monocytes and macrophages. Eosinophils, which comprised only a minor fraction of cells in the spleen, and erythroid series cells, which were detected in comparable numbers, are not depicted.