Effect of catalase treatment on LTBMCs. (A) Nonadherent cells recovered in control and catalase-treated (100 μg/mL) cultures (mean per culture ± SD). Low-density, nonadherent cells were cultured as described in “Materials and methods.” Each point is the mean of 3 to 5 replicate cultures. The results illustrated are representative of those found in greater than 10 repetitions of this experiment. (B) Wright-Giemsa-stained cytospin of the nonadherent cells removed from the culture after 1 week. There is a preponderance of granulocytes at varying stages of maturation. Original magnification, × 600; 60×/1.40 numeric aperture (NA) objective on a Leitz ortholux microscope (Leica Microsystems, Bannockburn, IL) and a Nikon D100 digital camera (Melville, NY). (C) Photomicrograph of phase contrast images showing differences in control and catalase-treated (100 μg/mL) cultures after 24 days of culture. Original magnification, × 100; 10 ×/0.25 NA objective. ^* indicates the cobblestone areas. The images were obtained using a Nikon D100 digital camera mounted on a Nikon inverted microscope. (D) CFU-Cs in the nonadherent cells recovered from control and catalase-treated (100 μg/mL) cultures. (E) Wright-Giemsa-stained cytospin of the nonadherent cells removed from the culture illustrated in panels A and D after 3 weeks. Almost all of the cells appear to be mature monocytes and/or macrophages. Original magnification, × 600 as described. (A, D) Error bars indicate SD of the mean.