Fig. 4. Depletion of IL-4 increases germinal center formation.

Cryosections of spleens from mice vaccinated with OXY-sKLH ± αIL-4 were stained for GL7⁺ germinal center B cells, IgD⁺ follicular B cells, and CD21/35⁺ follicular dendritic cells. Slides were imaged at ×20 magnification with a Zeiss widefield fluorescence microscope. (a) Representative image of germinal centers and surrounding follicle from mice immunized with OXY-sKLH ± αIL-4. Germinal centers are outlined in red. At 10 days post-vaccination: (b) overall number of follicles per imaged spleen section, (c) germinal centers per follicle, and (d) average GL7^high fluorescent area per germinal center was measured. Scale bars are 100 μm. Data are mean ± SEM. Sample size: n = 3 mice per group × 3 slides per mouse, with slices at least 100 μm apart. Statistical analysis conducted by Mann–Whitney U test. Symbols: **p ≤ 0.01.