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Overview of the Spleen


Harry S. Jacob

, MD, DHC, University of Minnesota Medical School

Reviewed/Revised Mar 2023

By structure and function, the spleen is essentially 2 organs:

  • The white pulp, consisting of periarterial lymphatic sheaths and germinal centers, acts as an immune organ.

  • The red pulp, consisting of macrophages and granulocytes lining vascular spaces (the cords and sinusoids), acts as a phagocytic organ.

The red pulp removes antibody-coated bacteria, senescent or defective red blood cells (RBCs), and antibody-coated blood cells (as may occur in immune cytopenias such as ITP Immune Thrombocytopenia (ITP) Immune thrombocytopenia (ITP) is a bleeding disorder usually without anemia or leukopenia. Typically, it is chronic in adults, but it is usually acute and self-limited in children. Spleen size... read more Immune Thrombocytopenia (ITP) , Coombs-positive hemolytic anemias Autoimmune Hemolytic Anemia Autoimmune hemolytic anemia is caused by autoantibodies that react with red blood cells at temperatures ≥ 37° C (warm antibody hemolytic anemia) or < 37° C (cold agglutinin disease). Hemolysis... read more Autoimmune Hemolytic Anemia , and some neutropenias Neutropenia Neutropenia is a reduction in the blood neutrophil count. If it is severe, the risk and severity of bacterial and fungal infections increase. Focal symptoms of infection may be muted, but fever... read more ). The red pulp also serves as a reservoir for blood elements, especially white blood cells (WBCs) and platelets. Macrophages derived from blood monocytes and resident macrophages produced during embryonic development can be activated to amplify control of infection, but they can also produce substances that induce unwanted excessive inflammation.

In some animals, the spleen can contract at times of severe anemia and "autotransfuse" red cells; whether this "autotransfusion" occurs in humans is unclear. Using its culling and pitting functions for RBCs, the spleen removes inclusion bodies, such as Heinz bodies (precipitates of insoluble globin), Howell-Jolly bodies (nuclear DNA remnants), whole nuclei, and malformed RBCs; thus, after splenectomy or in the functionally hyposplenic state, RBCs with these inclusions and acanthocytes (a type of malformed RBC) appear in the peripheral circulation. Extramedullary hematopoiesis may occur if injury to bone marrow (eg, by fibrosis or tumor metastases) allows hematopoietic stem cells to circulate and populate the adult spleen or if stimulated by therapy with hematopoietic growth factors (see also Primary Myelofibrosis Primary Myelofibrosis (PMF) Primary myelofibrosis (PMF) is a chronic myeloproliferative neoplasm characterized by bone marrow fibrosis, splenomegaly, and anemia with nucleated and teardrop-shaped red blood cells. Diagnosis... read more and Myelodysplastic Syndrome Myelodysplastic Syndrome (MDS) The myelodysplastic syndrome (MDS) is group of clonal hematopoietic stem cell disorders typified by peripheral cytopenia, dysplastic hematopoietic progenitors, a hypercellular or hypocellular... read more ).

Accumulating evidence suggests that there is communication between the brain and spleen, which has been termed the brain-spleen axis. Afferent and efferent vagus nerve signaling contributes to this communication. Chronic stress has been shown to produce splenomegaly in rodents, which can be blocked by the antidepressant arketamine. The spleen can affect the humoral immune response in corticotropin-related neurons in some areas of the brain. Splenectomy or splenic denervation has been shown to prevent stress-related depression in laboratory animals (1 General reference By structure and function, the spleen is essentially 2 organs: The white pulp, consisting of periarterial lymphatic sheaths and germinal centers, acts as an immune organ. The red pulp, consisting... read more ).


Asplenia is loss of splenic function due to

  • Congenital absence of the spleen

  • Functional absence of the spleen

  • Surgical removal of the spleen (splenectomy)

Because of the risk of these infections, immunization is important. Patients should receive the pneumococcal vaccine Pneumococcal Vaccine Pneumococcal disease (eg, otitis media, pneumonia, sepsis, meningitis) is caused by some of the > 90 serotypes of Streptococcus pneumoniae (pneumococci). Vaccines are directed against... read more , the meningococcal vaccine Meningococcal Vaccine The meningococcal serogroups that most often cause meningococcal disease in the United States are serogroups B, C, and Y. Serogroups A and W cause disease outside the United States. Current... read more , and the Haemophilus influenzae b vaccine Haemophilus influenzae Type b (Hib) Vaccine Haemophilus influenzae type b conjugate vaccine helps prevent Haemophilus infections but not infections caused by other strains of H. influenzae bacteria. H. influenzae... read more . Patients should also receive the influenza vaccine Influenza Vaccine Based on recommendations by the World Health Organization and the Centers for Disease Control and Prevention (CDC), vaccines for influenza are modified annually to include the most prevalent... read more , the COVID-19 vaccine COVID-19 Vaccine COVID-19 vaccines provide protection against COVID-19, the disease caused by infection with the SARS-CoV-2 virus. Vaccination is the most effective strategy to prevent severe illness and death... read more , and other vaccinations according to their clinical situation. Patients also are often given daily prophylactic antibiotics such as penicillin or amoxicillin, particularly when they have regular contact with children. The appropriate duration for prophylactic antibiotic use is unclear because the liver can take over the microbial clearing function of the spleen over time. Patients with asplenia who develop fever often receive empiric antibiotics while undergoing evaluation for the source.

General reference

  • 1. Wei Y, Wang T, Liao L, et al: Brain-spleen axis in health and diseases: A review and future perspective. Brain Res Bull 182:130–140, 2022. doi:10.1016/j.brainresbull.2022.02.008

Drugs Mentioned In This Article

Drug Name Select Trade
Pneumovax 23, Pnu-Imune-23 , Prevnar, Prevnar 13 , Prevnar 20, VAXNEUVANCE
Amoxil, Dispermox, Moxatag, Moxilin , Sumox, Trimox
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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