Normal leukocyte and T-cell numbers. (A) White blood cell (WBC) counts are unaltered in CD44^−/− mice. Mice were injected twice daily for 4 days with G-CSF. Control mice were injected with PBS, indicated as day 0. Mice were sacrificed at days 5 and 7 after the start of G-CSF treatment, and peripheral blood was collected individually by heart bleeding. White blood cells were analyzed with a Coulter counter (Coulter, Miami, FL) calibrated for mice cells. Results from individual mice are shown. CD44^−/−, open triangles and CD44^+/−, closed triangles. Average white blood cells are indicated with bars and values. (B) Normal T-cell subsets in thymus, lymph nodes, and spleen. Different organs were used to examine T cells from CD44^+/+, CD44^+/−, and CD44^−/− mice. Thymocytes, lymph node, and spleen cells were stained with PE-conjugated anti-CD8 and FITC-conjugated anti-CD4. No detectable difference was seen in total T-cell number or CD4/CD8 ratio in these organs. FCM data were collected for viable lymphocytes according to SSC and FSC.