The spleen placed under the rib cage on the left side of the abdomen is often ignored until it is compromised. Nevertheless, this organ plays an important role in our immune system, acting as a watchdog and orchestrator of defense against invading microbes. In this blog, we will highlight the complex functions of the spleen, its importance in the immune response, and the profound consequences that arise when it suffers from injury or weakness.
Introduction
The spleen is not just a reservoir for blood or an inactive organ. It acts as a dynamic center of immune activity, filtering the blood to remove old or damaged red blood cells, while simultaneously increasing the immune response against infection. This dual role places it as an important component in our body's defense weapons.
Body composition and structure of the spleen
The anatomical structure of the spleen reflects its multifunctional functions. It consists of two distinct regions: red pulp, where aged blood cells are broken down and recycled, and white pulp, which contains important immune cells for detecting and combating pathogens.
In the red pulp, macrophages engulf and digest the cracked red blood cells, clear the iron and bring the nutrients back into circulation. Meanwhile, white pulp is rich in lymphocytes — B cells and T cells — that patrol for antigens, initiate an immune response, and coordinate favorable immunity.
Immune functions of the spleen
- The immune functions of the spleen are diverse and essential:
- Antibody production: B cells within the white pulp produce antibodies that are specific to exposed microbes.
- Antigen presentation: Dendritic cells and macrophages capture and present antigens to T cells, enabling them to enhance the targeted immune response.
- Filtering and clearance: The spleen acts as a filter, trapping germs and debris from the blood, preventing their spread.
When the spleen is removed, the liver can take over most of spleen's tasks. Due to the importance of the spleen in the body's defense against germs, the person is at a risk of becoming infected after the surgery. The spleen serves as a blood reserve for the body, the risk of severe blood loss is higher.
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What impact would this have on host defenses?
The spleen's role in the defense system is to store nearly one-third of the human body's total blood platelets. The platelet count in the blood increases after the spleen is removed. This disorder is known as thrombocytosis, and it can cause irregular blood clotting, which can be fatal.
Since the spleen is so close to the lungs, there will always be the risk of lung collapse once it is removed. It can also cause pneumonia and a build-up of fluid in the lungs. A high platelet count is frequently associated with infection. This is mainly caused by cytokines, which are substances released as part of the body's regular response against infection.
In splenectomized patients, the occurrence of severe infections is higher. The spleen, as the largest single component of the phagocytic mechanism, is essential for phagocytosis of particles that have not been properly opsonized. These are carried up by macrophages, digested, and expressed on the macrophage membrane together with HLA system determinants. T cells respond by proliferating in response to these structures, triggering several immunoregulatory mechanisms.
The spleen's anatomical architecture permits macrophages and T cells to come into proximity, as a result, splenectomy is a significant immunologic intervention. Low IgM concentrations, decreased generation of antibodies directed against pneumococci and Escherichia coli, and multiple abnormalities in cellular immunity, including decrease numbers of T cells and a reduction in lymphocyte proliferative responses, have all been seen in splenectomized patients. As a result, removing the spleen alters specific immune reactions, as seen by a variety of clinical symptoms.
A blood clot in the vein that transports blood to the liver,
a hernia at the insertion site, an underlying infection, a collapsed lung,
injury to the organs near your spleen, such as the stomach, colon, and
pancreas, and an accumulation of pus under your diaphragm are all risk factors.
In children splenectomy leads to bacterial sepsis caused by Pneumococci,
Meningococci and H. Influenzae. Vaccines or prophylactic injections for
pneumonia, meningitis, and influenza can be given prior to, or shortly after,
surgical removal of the spleen to reduce the risk.
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Tabulated breakdown of the impact of spleen removal on host
defenses:
| Aspect of Host Defense | Impact of Spleen Removal |
|---|---|
| Blood Filtration | Reduced ability to filter and remove old or damaged red blood cells |
| Immune Response | Decreased ability to mount an effective immune response |
| Antibody Production | Impaired production of antibodies, especially against blood-borne pathogens |
| Pathogen Clearance | Reduced ability to clear certain bacterial and parasitic infections |
| Storage of Blood Cells | Loss of spleen as a reservoir for platelets and some white blood cells |
| Hematopoiesis Regulation | Minimal impact, as the spleen's role in hematopoiesis is limited |
- Stability: Early stabilization focuses on controlling bleeding and preventing trauma.
- Surgical intervention: Depending on the severity, surgical repair (splenorectomy) or removal (splenectomy) may be necessary to prevent further complications.
- Vaccination: Vaccination against bacteria such as pneumococcus and meningococcus is essential to reduce the risk of infection.
- Antibiotic prophylaxis: Prophylactic antibiotics may be prescribed in some cases to further reduce susceptibility to infection.
- Patient Education: Educating patients and caregivers about recognizing the symptoms of infection and seeking immediate medical attention is important for early intervention.
- Regenerative medicine: Advances in tissue engineering and stem cell therapy aim to restore spleen function or create an artificial spleen-like structure.
- Immunomodulatory therapies: New therapies targeting immune dysfunction after splenectomy promise to improve outcomes for those affected.
- OpenStax College, Anatomy and Physiology. OpenStax CNX.
- Prescott, Harley & Klein, Microbiology, Willey J, Sherwood L and Woolverton C, 2017.
- Microbiology, 10th edition. McGraw-Hill, New York, USA. ISBN 9789813151260
- http://cnx.org/contents/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@11.1.
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4 Comments
What are the factors influencing the extent and severity of infection , explain?
ReplyDeleteThe extent and severity of infection following spleen injury or splenectomy are influenced by the interplay of these factors. Anatomically, the loss of spleen's filtering function and immune surveillance disrupts the body's first line of defense against pathogens. Immunologically, impaired antibody production and antigen presentation further compromise the ability to mount effective immune responses. Clinically, individuals who undergo splenectomy require lifelong precautions, including vaccination against encapsulated bacteria and prompt medical attention for any signs of infection, to mitigate the heightened risk of serious infections.
DeleteDiscuss factors affecting immune responses
ReplyDeleteThe immune response is a complex process that is influenced by a number of factors. Some of the most important factors affecting immune responses include:
DeleteAge: As people age, their immune response can become less effective, making them more susceptible to infections and illnesses.
Genetics: Some people have a genetic predisposition to certain immune disorders, such as autoimmune diseases or a weakened immune system.
Nutrition: A well-balanced diet is important for maintaining a healthy immune system. Deficiencies in certain nutrients, such as vitamins A, C, and E, as well as zinc, iron, and selenium, can weaken the immune response.
Stress: Chronic stress can weaken the immune response and make people more susceptible to infections and illnesses.
Sleep: Getting adequate sleep is important for maintaining a healthy immune system. Chronic sleep deprivation has been shown to impair the immune response.
Physical activity: Regular exercise has been shown to improve the immune response, but excessive physical activity or overexertion can have the opposite effect.
Smoking and alcohol consumption: Smoking and excessive alcohol consumption have both been shown to impair the immune response.
Environmental factors: Exposure to pollutants, toxic substances, and other environmental factors can weaken the immune response.
Chronic medical conditions: Chronic medical conditions, such as diabetes, HIV/AIDS, and cancer, can weaken the immune response and make people more susceptible to infections and illnesses.
Medications: Certain medications, such as corticosteroids and chemotherapy drugs, can suppress the immune response and make people more susceptible to infections and illnesses.