The white pulp of the spleen is most associated with which component?

• A. Red pulp
• B. White pulp
• C. PALS
• D. Trabeculae

Answer: (B)

Think of the spleen as having two main neighborhoods: white pulp and red pulp. The white pulp is a lymphoid tissue organized around central arteries, meaning its defining feature is a T-cell–rich zone that surrounds these arteries. This T-cell–dense area is called the periarteriolar lymphoid sheath, or PALS. Around PALS, you also find B-cell zones known as lymphoid follicles, which can develop germinal centers during immune responses. The marginal zone sits at the border between white and red pulp and contains specialized macrophages and B cells but is not the hallmark structure of the white pulp itself. In contrast, the red pulp handles filtering of blood cells and houses splenic cords and sinusoids, while trabeculae are the connective tissue scaffolding of the spleen. So, the white pulp is most closely associated with the PALS because that periarteriolar lymphoid sheath is the defining T-cell–rich component surrounding the central arteries within this region.