FIG. 3.

Metronidazole treatment alters the homeostatic balance of the distal colon. (A) H&E-stained distal colon sections from untreated and streptomycin- and metronidazole-treated mice at day 0. No overt inflammation evident. Original magnification, ×400; bars, 50 μm. (B) Quantitative RT-PCR results of IL-25 (*, P = 0.0371), Reg3γ (*, P = 0.0177); and TSLP expression in the distal colon of untreated and streptomycin- and metronidazole-treated mice. Results are averaged from three independent experiments (n = 4 to 6 mice per group). U, untreated mice. (C and D) FACS analysis of macrophage, NK cell, and T cell recruitment to the lamina propria (C) and spleen (D) in untreated and metronidazole-treated mice. Both splenic and lamina propria cells were stained with fluorescently labeled CD45, CD3ɛ, CD49b, and F480. Only CD45-positive cells were examined for the expression of CD3ɛ, CD49b, and F480. T cells are defined as CD45⁺ CD3ɛ⁺ CD49b⁻; NK cells are defined as CD45⁺ CD3ɛ⁻ CD49b⁺; macrophages are defined as CD45⁺ F480⁺. (E) Flow cytometric analysis of CD49b⁺ and F480⁺ populations within the CD45⁺ lymphocytes in the lamina propria and spleen of untreated and metronidazole-treated mice. Data from one mouse per group are shown and are representative of 2 independent experiments (n = 4 per group).