Spleen: A new role for an old player?

Table 1 Histology of spleen

Anatomy	Composition
Red pulp	“Sinusoids” which are filled with blood
	“Splenic cords” of reticular fibers
	“Marginal zone” bordering on white pulp
White pulp	Nodules, called Malpighian corpuscles, containing “lymphoid follicles”
	rich in B-lymphocytes
	“periarteriolar lymphoid sheaths”, plenty of T-lymphocytes

Table 2 Function of the spleen

Red pulp

Extramedullary hematopoiesis if required

Facilitating an environment wherein erythrocytes rid themselves of solid waste material

Blood filter for foreign material and damaged and senescent blood cells

Storage site for iron, erythrocytes, platelets, plasmablasts and plasma cells

Rapid release of antigen-specific antibodies into the circulation produced by red pulp plasma cells

Defense against bacteria using iron metabolism by its macrophages

White pulp

T cell zone (periarterial lymphatic sheath) and B cell zone (follicles)

Storage site for B and T lymphocytes

Development of B and T lymphocytes upon antigenic challenge

Release of immunoglobulins upon antigenic challenge by B lymphocytes

Production of immune mediators involved in clearance of bacteria such as complement, opsonins, properdin and tuftsin

Marginal zone

Phagocytosis of circulating microorganisms and immune complexes by MZ macrophages

Development of marginal zone B lymphocytes upon TI-2 antigenic challenge

Blood trafficking of B and T lymphocytes

Release of immunoglobulins upon antigenic challenge by splenic B lymphocytes