Located in LUQ of abdomen, anterior to left kidney, protected by 9th-11th ribs.

Sinusoids are long, vascular channels in red pulp with fenestrated "barrel hoop" basement membrane.

- T cells are found in the periarteriolar lymphatic sheath (PALS) within the white pulp.- B cell are found in follicles within the white pulp.- The marginal zone, in between the red pulp and white pulp, contains macrophages and specialized B cells, and is where antigen-presenting cells (APCs) capture blood-borne antigens for recognition by lymphocytes.

Splenic macrophages remove encapsulated bacteria.

Splenic dysfunction (eg, postsplenectomy state in sickle cell disease): ↓ IgM → ↓ complement activation → ↓ C3b opsonization → ↑ susceptibility to encapsulated organisms.Postsplenectomy blood findings:- Howell-Jolly bodies (nuclear remnants)- Target cells- Thrombocytosis (loss of sequestration and removal)- Lymphocytosis (loss of sequestration)Vaccinate patients undergoing splenectomy against encapsulated organisms (pneumococcal, Hib, meningococcal).