Question

The white pulp of spleen appears purple in H & E preparations; justify please.
​

Answer 1

White pulp is a histological designation for regions of the spleen (named because it appears whiter than the surrounding red pulp on gross section), that encompasses approximately 25% of splenic tissue. White pulp consists entirely of lymphoid tissue.

more details:

Specifically, the white pulp encompasses several areas with distinct functions:

• The periarteriolar lymphoid sheaths (PALS) are typically associated with the arteriole supply of the spleen; they contain T lymphocytes.
• Lymph follicles with dividing B lymphocytes are located between the PALS and the marginal zone bordering on the red pulp. IgM and IgG2 are produced in this zone. These molecules play a role in opsonization of extracellular organisms, encapsulated bacteria in particular.
• The marginal zone exists between the white pulp and red pulp.[1] It is located farther away from the central arteriole, in proximity to the red pulp. It contains antigen-presenting cells (APCs), such as dendritic cells and macrophages. Some of the white pulp's macrophages are of a specialized kind known as metallophilic macrophages

Macrophages in the white pulp:

The T cell zone (periarteriolar sheath) and B cell follicles contain discrete macrophage populations; however, not much is known about these macrophage populations in terms of their origin and lifespan. These macrophages are not unique to the spleen but instead make up an integral part of the lymphoid parts of all secondary lymphoid organs.

$\:$