lymphoid system Flashcards
atherosclerosis
Plaque forms in lamina propria, facilitated by excess LDL
- Macrophages engulf LDL, turn into foam cells
- Inflammation attacking foam cells
- Narrowing of vessel
innate immunity (speed, specificity, initiated and facilitated by which cells?)
- rapid
- non-specific elimination of pathogens
- Initiated: neutrophil, macrophage phagocytosis
- complement and TLRs also rapidly initiate innate resp
- Facilitated: granulocytes
adaptive immunity (speed, specificity, mediated by which cells?)
- Slow
- specific epitopes targeted (antigens)
- Mediated: B and T cells
complement proteins
Rapidly initiate innate resp
- Plasma proteins, prod in liver
- released into c. tissue when bl vessel is injured
- bind to pathogen lipids/carbs
- bind to macrophage/neutrophil receptor
TLRs
Rapidly initiate innate resp
- Surf on macrophages and neutrophils
- recognize various pathogen molecs non-specifically (bacteria, yeast, viruses)
Inflammation (where it can occur, signs in histology, how are WBCs recruited?)
Strong innate resp in c. tissue
Many WBCs in c. tissue (basophilic nuclei, blue)
- WBCs (granulocytes and agranulocytes) recruited with cytokines and APCs
cytokines
Interleukins: released by macrophages and neutrophils
Interferons: released by NK cells
- Attract WBCs
- WBCs exit blood by diapedesis
Antigen presenting cells
Dendritic, monocytic, macrophage cells
- present Ags to lymphocytes
- Also exit blood by diapedesis
diapesis/extravasation
Adhesion + migration of leukocytes across post-capillary venule wall to enter c. tissue
- leukocytes tether and roll along endothelium via selectins
- Strong adhesion and migration via integrins
dendritic cells
Bridge innate and adaptive resp
- Derived from monocytes/macrophages in tissues
- Digest foreign proteins + carbs
- present digested bits to lymphocytes
primary lymphoid organs
Site of lymphocyte prod
- B cells: BM
- T cells: BM + thymus
secondary lymphoid organs
Sites of lymphocyte activation w foreign pathogens
- Lymph nodes
- MALT
- Spleen
lymph nodes
In lymph vascular flow
- CT capsule (dense, irregular) and trabeculae
- Reticular CT (collagen III) stroma
- Enter via afferent lymphatics, exit via efferent lymnphatics
- Cortex: B cells, incl germinal centers (where B cells get activated)
- Paracortex: T cells
mucosa associated lymphoid tissue
Sub-epithelial lymphoid aggregates in mucosal CT
- No CT capsule, not in lymph flow
- Lamina propria of GI, respiratory, genitourinary tracts
- B + T cell activation
- blood vessels + efferent lymphatic
spleen
Activates lymphocytes (white pulp, basophilic) and destroys aged blood cells (red pulp, eosinophilic)
- CT capsule, not in lymph flow
- Reticular fibers (collagen III)
- central arteriole supplies blood to venous sinusoids
In white pulp: germinal center and PALS
B cell initial development
In BM: lymphocytes proliferate and restrict lineage to B-lymphocytes (all clones)
pre-B cell formation
In BM: Single set of Ig genes is rearranged, inserted into plasma membrane => naive pre-B cell
B cell screening
In BM: If Ig interacts with self-Ag in BM, apoptosis occurs
B cell activation
naive B cells leave BM via venous sinusoids, activated by Ags in 2* lymphoid organs
- When activated, produce soluble Igs
T cell initial development
In BM: lymphocytes proliferate and restrict lineage to T-lymphocytes (all clones), migrate to thymus
pre-T cell formation
In thymus: Single set of TCR genes in rearranges, inserts into plasma membrane
- Can recognize single, specific antigen presented by APCs
- naive pre-T cell
T cell screening
In thymus: if pre-TCR interacts w self-Ag presented by APCs, apoptosis
T cell activation
Naive T cells leave thymus via post-capillary venules (extravasation) at corticomedullary junction
- activated by APCs in 2* lymph organs
Trabeculae/Septae
Dense irregular c. tissue capsule of thymus, demarcated lobules
thymic cortex
In each lobule,
- Basophilic (blue) cortex
- Developing T cells
thymic medulla and hassall’s corpuscules
In each lobule,
- Eosinophilic (pink) medulla
- Pink Hassall’s corpuscules
- Clusters of reticular epithelial cells (net like formation)
- Produce cytokines (thymopoietin) for T cell development
post-capillary venules
In thymus at corticomedullary junction
- No blood-thymus barrier
- T-lymphocytes enter thymus here
- naive T cells exit thymus here
Epithelial reticular cells
Surround continuous capillaries to protect developing T cells in thymus (blood-thymus barrier)
lymph vascular system
Moves lymph from CT to venous system
- Begins as lymphatic capillaries, empties into subclavian veins at root of neck
lymphatic capillaries
Blind ended, one way flow tissue -> capillary
- Clefts between endothelial cells to facilitate movement in/out (no tight junctions)
lymph fluid
Lymph interstitial fluid (plasma-like), antigens, lymphocytes, APCs
collecting lymph vessels
continues from lymphatic capillaries
- Thin walled tunica intima, media, and adventitia
- Tunica intima forms one-way valves in direction of flowing back to venous system
movement of lymph through lymph node
Lymph fluid: afferent vessel -> cortex -> paracortex -> medulla -> efferent vessel
B + T cells: enter and exit via post-capillary venules in paracortex
plasma b cells
secrete Abs
memory b cells
initiate rapid 2* response
LN cortex
B cell activation (germinal centers)
LN paracortex
T cell activation
marginal zone (spleen)
between red and white pulp
- D cells present Ags to lymphocytes
- Macrophages destroy bad/old RBCs
Periarterial lymphatic sheath (PALS)
T cell zone in spleen’s white pulp
