Fig. 1.

Diagram of the normal spleen parenchyma (rat). Blue regions depict features within the white pulp whilst red regions depict the red pulp. The white pulp is composed of multiple lymphoid follicles. A follicle consists of a reactive germinal center (GC) surrounded by a mantle zone (MN) and marginal zone (MZ). There are arterioles (A) adjacent to or within the white pulp. Lymphoid tissues envelope the arterioles to form periarteriolar lymphoid sheath (PALS). The white pulp regions are analogous to “buds” whereas the arterioles are analogous to “branches”. The red pulp is distributed as sinuses and solid-appearing cords, which separate the white pulp