Lecture 23: Cells Of The Lymphatic System Flashcards
Define and explain the functions of lymphatic system
1) Protect body against pathogens or antigens
Basis for this self-defense – distinguish self from non-self
Describe the morphology and functions of cells of the lymphatic system including CD4+ & CD8+ T cells, B cells & plasma cells
and natural killer cells.
1) Helper CD4+ –> T-cells, mature in thymus = immunocompetent, Presents on MSC2,
Types:
-TH1: Produces interleukin 2 (IL2) to interact w CD8+ –> Destroy INTRAcellular antigens
-TH2: Produces IL4, IL5, IL10, IL13 to activate B-lymphocytes –> destroy EXTRAcellular antigens
2) Cytotoxic CD8+ –> T-cells, mature in thymus = immunocompetent, Destroys antigens, Presents on MSC2
4) B cells –> Carried in blood, spleen, connective tissue, when activated by CD4+
- -> Plasma cells
5) Plasma cells –> Produce antibodies against specific antigens
6) Natural killer cells. –> Attack virus- infected cells and cancer cells
List and describe the types of immune response.
1) Innate Response (Non-specific):
- neutrophils, macrophages, mast cells
- Fast and nonspecific
- No memory cells
2) Adaptive Response (Specific Immunity):
- B and T cells
- Slower and specific
- Produces memory cells” Primary and secondary response
3) Antibody mediated Immunity
- Helper T-cells, B-cells, plasma cells
- Releases antibodies that invade organ
4) Cell Mediated Immunity
- Specific T cells that specialize in cytotoxicity (Granzymes, Perofins)
List and compare the primary and secondary lymphoid organs.
1) Primary organs
- Bone marrow
- Thymus
- GALT
2) Secondary lymphoid organs
- Lymph nodes
- Spleen
- Tonsils
Compare primary and secondary lymphatic nodules and describe their structural organization
Nodule = collection of lymphocytes
1) Primary nodule
- Small lymphocytes
- Not challenged by antigen
2) Secondary nodule:
- Consists of germinal center (GC)- area where lymphocytes undergo proliferation (Paler region)
- GC –> indicated lymphatic tissue response to antigen(Called mantle zone/corona)
Explain concepts of BALT, MALT and GALT.
1) MALT (mucosa associated
lymphoid tissue)
-Diffused lymphoid tissue
2) BALT
3) GALT
- Primary lymphoid Organ
Identify & describe the structures and function of the thymus.
Function:
- Lymphocytes differenciate and enlarge, Mature T Cells migrate into medulla blood vessels and efferent lymphatics
- Primary lymphoid organ
Location:
-superior mediastinum
(Origin = 3rd pharyngeal pouch)
Structure:
1) Capsule
2) Trabequle
3) Cortex:
- Tightly packed lymphocytes and support cells (Reticular cells)
- Outside
4) Inner Medulla:
- Lymphocytes less concentrated
- Pale staining (ERC–> Eosinophilic)
Describe the formation of the blood thymus barrier and its significance
- ERC Type 1 form a sheath preventing antigens in the blood from contacting the thymocytes
- In the cortex
Identify & describe the structures and function of a lymph node
Identify Structure:
- Kidney/bean shaped
- Made up of B-lymphocytes
1) Capsule
- dense connective tissue, pierced by afferent lymphatics
2) Outer Cortex
- Abundance of B Lymphocytes
3) Inner Cortex/Para cortex
- No nodules
- T-lyphocytes
- High endothelial venules (HEV)–> allows transition of lymphocytes from the blood stream to lymph tissue within lymph nodes
4) Medulla
-Cords –> contain primarily B lymphocytes,
plasma cells, reticular cells and
macrophages
-Sinuses –> Space separating chords, contains: Lymph/macrophages/(May have granulocytes during draining of infected region)
5) Hilum (Efferent lymphatics)
-blood vessels and nerves
(enter and leave) : lymphatics exit
Function:
-Filters lymphatic fluid as it passes through them
Describe the flow of lymph through a lymph node and explain the significance of subcapsular sinus.
Flow:
Afferent lymphatic vessels –> Subcapsular (cortical) sinus –>Trabecular sinus –> Medullary sinus –> Efferent lymphatic vessel
Subscapular sinus: -Space under the capsule -Composed of loose reticular cells and fibers- slowing down of lymph -Foreign antigens are captured by macrophages in this region. Present the antigens to lymphocytes -Activation of lymphocytes
Describe the cellular distribution in a lymph node and explain the significance of the stroma.
- Reticular cells (modified fibroblasts) produce the stroma
- Silver stain used to identifiy reticular fribers
What are the cells in a lymphatic nodule
1) Lymphocytes :
➢ B lymphocytes
➢ Activated > proliferate >plasma cells
& memory cells
2) Reticular cells:
➢ Produce reticular fibers (stroma)
3) Dendritic follicular cells:
➢ Most efficient APCs
➢ Present antigens on MHC I & II
molecules
4) Macrophages:
➢ Phagocytic & APC (contain MHC I
& II molecules)
5) Follicular dendritic cells:
➢ Dendritic in nature: lack MHC II
molecules: harbors Ag-Ab complexes
