WASp deficiency leads to abnormal spleen architecture with delayed GC reaction. Wild-type (WT) and WASp-deficient (WASp–) mice were immunized by intraperitoneal injection of SRBCs. Mice were killed on indicated days and cryostat sections of spleens were prepared. (A) Representative images of spleen sections are shown. Spleens were analyzed on day 5 or 10 after SRBC immunization (diluted 1:10). B- and T-cell areas were stained with PE-labeled anti-B220 (red) and Cy5-labeled anti-CD3 (blue) antibodies, respectively, and GCs were detected with biotinylated PNA, followed by streptavidin-FITC (green). (B) Quantitative determination of white pulp areas. Spleens from mice immunized with a 1:10 dilution of SRBCs (day 4 to 10) or a 1:100 dilution of SRBCs (on day 6) were analyzed. The B-cell, T-cell, and GC area was measured on images of random sections. The percentages of B-cell, T-cell, and GC areas of the total spleen area are shown. Each bar represents mean values from measurements of 3 different spleens. Error bars show one SD and asterisks indicate a significant difference of P < .05 using a 2-tailed t test. Presented results are representative of 3 similar experiments. Upper images show day 5, and lower images, day 10.