Abolished immune response in mice reconstituted with WASp-deficient bone marrow. Bone marrow cells from wild-type (WT) and WASp-deficient (WASp–) mice were injected intravenously into irradiated wild-type recipient mice. At 8 weeks after reconstitution, mice were immunized by intraperitoneal injection of SRBCs diluted 1:10. Spleens were analyzed on day 4 or 6 after immunization. (A) Representative images of spleen sections are shown. B-cell, T-cell, and GC areas were stained as in Figure 3. (B) Quantitative determination of white pulp areas. The B-cell, T-cell, and GC area was measured on images of random sections. The percentages of B-cell (top), T-cell (middle), and GC (bottom) areas of the total spleen area are shown. Each bar represents mean values from measurements of 4 (day 4) or 3 (day 6) different spleens. Error bars show one SD and asterisks indicate a significant difference of P < .01 using a 2-tailed t test. (C) Individual antibody-secreting cells were enumerated from spleens of immunized mice, using the hemolytic plaque assay. Numbers of direct PFCs detecting IgM-secreting cells and indirect PFCs detecting IgG-secreting cells are shown. Each bar represents the mean value from 4 (day 4) or 3 (day 6) mice. Error bars show one SD and asterisks indicate a significance level of P < .01 using a 2-tailed t test. (D) T-cell proliferation in reconstituted mice. T cells from spleens were stimulated with anti-CD3 antibodies (αCD3, 10 μg/mL) or concanavalin A (Con A, 4 μg/mL). Note the reduced proliferative response of T cells from recipients that received WASp– bone marrow. Equal levels of proliferation in response to PMA/ionomycin are used as a control for cell numbers. Each bar represents the mean value of triplicates; error bars show one SD; and asterisks indicate P < .01 using a 2-tailed t test.