WBCs, Spleen, Immune System Flashcards
3 Functions of Immune System
- protect from foreign substances
- tumor surveillance
- self-recognition
Components of the Immune System
- tissues: eg bone marrow, thymus, spleen
- cells: eg leukocytes, macrophages, APCs
- proteins: eg immunoglobulins
Function of the Complement System
- protect intravascular space from bacterial infection
- clear tissue debris
- wound healing
Humoral Immunity Flow Chart
B cells –> plasma cells –> antibodies
Cellular Immunity Flow Chart
T cells –> cytotoxic, activate phagocytes (macrophages), direct the humoral immune response
3 Normal Functions of the Spleen
- hematopoiesis
- filtering
- immune defense
Hematopoiesis in the Spleen
- important blood producing organ in the fetus
- extramedullary hematopoiesis can cause splenomegaly
Filtering by the Spleen
- filters old and poorly deformable RBCs
- removal of particles from RBCs like nuclear remnants and insoluble globin proteins
Immune Defense by the Spleen
- spleen is largest lymphoid organ
- sinusoids clear bacteria from circulation
- mononuclear phagocytes process foreign material
- very important in defense against encapsulated bacteria (H flu, S pneumo, Pneumococcus)
Major Causes of Splenomegaly
- liver dz: scarring in liver pushes blood back through the portal system
- hematologic malignancy
- infection/inflammation
- primary splen diz
Indications for Splenectomy
- immune cytopenias
- hematologic malignancy
- RBC membrane/enzyme disorders
- thalassemia
- TTP (thrombotic thrombocytopenic purpura)
- blunt trauma
Consequences of Splenectomy
- leukocytosis (increased WBC)
- thrombocytosis (increased plt 500-700,000)
- Howell Jolly bodies
- infection risk
Post Splenectomy Sepsis
- uncommon, but high mortality
- classically caused by encapsulated bacteria
How is post-splenectomy sepsis prevented?
- previously used abx prophylaxis, but not recommended
- now, vaccines
Neutrophil Function
-find, ingest and kill invading microorganisms
