Defective spleen organization in TNF/LTΔ3 mice. Magnifications are given on left. (A) Splenic cryosections of 6- to 8-week-old mice immunized with SRBC were stained to detect the distribution of T cells (CD3, blue) and B cells (IgD [brown], IgM), FDC (CR1), or stromal elements (ER-TR7) in TNF/LTΔ3 and single-knockout mice. WT, wild type. (B) Side-by-side comparison with TNF/LTα−/− mice. Splenic cryosections of 6- to 8-week-old nonimmunized mice were stained with anti-CD3 (blue), anti-B220 (brown), or anti-ER-TR7.