Peripheral blood counts are suppressed and lymphoid organs diminished with antibiotic therapy. (A) Hemoglobin, (B) white blood cell count and differential, and (C) platelet counts were determined for control (Ctrl) vs antibiotic-treated (Abx) mice using an automated hematologic cell counter. (D) Lymphocyte subsets and (E) CD4:CD8 ratio in peripheral blood for control vs antibiotic-treated mice were determined by flow cytometry. (F) Thymi and (G) spleens from control vs antibiotic-treated mice were weighed. Results are compiled from 3 independent experiments (n = 9-14 per group). Graphs show mean + standard error of the mean (SEM). Statistical significance was determined by Student t test. ns, not significant; *P < .05, **P < .01, ***P < .001, ****P < .0001.