Which two tissues served as positive control tissues for both NF-κB (p65) and CD11b+ cell staining?

• A. Spleen and tonsil
• B. Liver and spleen
• C. Lymph node and thymus
• D. Bone marrow and spleen

Answer: (A)

Selecting tissues that consistently show both NF-κB p65 and CD11b+ staining hinges on having abundant immune cells that express these markers. The spleen and tonsil fit this perfectly: they are rich in macrophages and dendritic cells (CD11b+ populations) and harbor active immune environments where NF-κB p65 is readily detectable in the nuclei of these cells. In the spleen, macrophages in the red pulp and antigen-presenting cells in the white pulp provide clear CD11b staining, while NF-κB p65 is present in the nuclei of these immune cells. Tonsil adds another robust site of macrophages and dendritic cells within mucosal-associated lymphoid tissue, again giving strong CD11b labeling and nuclear p65 signals. This combination yields reliable, reproducible positive staining for both targets, making these two tissues ideal positive controls.

Other tissues can be less reliable for dual optimization because their macrophage/dendritic cell content or NF-κB activity is more variable. For instance, some tissues may have fewer CD11b+ cells or less consistent NF-κB nuclear localization across samples, reducing the certainty of a positive control for both markers.