Intro (Ch 1)

Question 1

7 Properties of Adaptive Immunity

Answer 1

• Specificity - mult clones; ea clone has receptor for different antigen
• Diversity - clones against a diverse repertoire of antigens
• Memory - larger/more effective response to repeated exposure;
  
  • Primary immune response - naive lymphocytes
  • Secondary immune response - activate memory lymphocytes —> faster and larger response
  • Memory cells - were induced in primary response but long-lived; ea additional infection w/ same antigen makes more memory cells in addition to those that already exist
• Clonal Expansion -when lymphocytes are activated by antigens, they undergo proliferation, generating many thousands of clonal progeny cells, all with the same antigen specificity
• Specialization - different responses are unique to the microbe at hand
• Contraction and Homeostasis - immune response decreases as microbe is eliminated; return to baseline (self-limiting)
• Non-reactivity to Self - immunological tolerance

Question 2

3 Types of APCs

Answer 2

• Dendritic cells -present to T cells - have long processes off membrane
  
  • Capture microbes then bring to lymph nodes to present
• Macrophages
• Follicular dendritic cells - display to B cells in humoral response; reside in peripheral lymph tissues in lymphoid follicle and stimulate B cells there

Question 3

B Cell Maturation

Answer 3

• Guided by stream cells (create seal so no antigen exposure during maturation and secrete IL-7 to stimulate B cell receptor formation)
• Negative selection- apoptosis of B cells that recognize self-antigens

Question 4

T Cell Maturation

Answer 4

• Thymus made of lobes w/ outer cortex and inner medulla
• Immature T cells from bone marrow enter cortex —> proliferate there —> move deeper into cortex as they mature —> medulla
• Start as CD4-/CD8- THEN both CD4+/CD8+ THEN only positive for 1
• Stroma = just epithelial reticular cells (NO ECM)
  
  • Tight junctions to seal immature T cells from blood/foreign bodies (blood thyme barrier), secrete thymic hormones (thymopoiten and IL-7 for differentiation), present self antigens and MHCI/II molecules to immature T cells to assure recognition of self
• Positive selection - should tightly bind MHCI and MHC II (apoptosis)
• Negative selection - should NOT tightly bind other self-antigens (apoptosis)

Question 5

Hassall’s Corpuscles

Answer 5

• made up of stromal cells of medulla - secrete thymic stromal lymphopoiten (converts immature T cells —> Foxp3+ regulatory T cells)

Question 6

Function of Lymph Nodes + 3 Main Sections

Answer 6

• Encapsulated
• Encounter antigens filtered in lymph
• Cortex- contains primary follicles (clusters of B cells)
  
  • If B cell activated - form germinal center of proliferation into plasma cells and memory cells (secondary follicle)
• Paracortex - rich in T cells; were dendritic cells present to T cells
  
  • High endothelial venues for extravasation of B and T cells —> lymph node —> efferent lymphatic drainage —> circulation
• Medulla - entering and exiting blood vessels (how new mature B and T cells get in), lymphatic sinuses and medullary cords

Question 7

Spleen Function + 2 Pulps

Answer 7

• Encapsulated
• Encounters antigens in filtered blood
• White pulp (WBC)
  
  • Central artery (branches of splenic artery) covered in periarterial lymphatic sheaths (PALS) of mainly naive T cells
  • If B cell activation - germinal centers form on one side of central artery
  • Edges - marginal zone od dendritic APCs (sample antigens in blood for presentation)
• Red Pulp (RBC)
  
  • **Central artery splits into closed circulation OR open circulation
    
    • Closed circulation…Splenic sinusoids (capillaries w/ holes for RBCs to exit to circulation), splenic cords, pooled blood
  • Open circulation is where RNC turnover takes place…

Question 8

3 Reasons for RBC Turnover

Answer 8

• 1- spectrin degradation —> dec flexibility scant get through holes in caps
• 2- Transmembrane glycoproteins lose silica acid residues —> macrophages have receptors for asialoglycoproteins
• 3- dec in RBCs energy —> phosphatidylserines flip to outside of membrane; macrophages have receptors for these too

Question 9

3 By-products of RBC Turnover

Answer 9

• Iron bound to transferring
• Heme (converted to bilirubin —> liver to make bile)
• Globin chains (reduced to AAs)

Question 10

GALT and MALT

Answer 10

• GALT (Gut-Associated Lymphoid Tissue)
  
  • Filter antigens that come thru gut
  • Peyer’s Patches- nodules in SI where newly differentiated T cells are exposed to food antigens (develop oral tolerance- prevent widespread food allergies)
• MALT (Mucosal-Associated Lymphoid Tissue)
  
  • Non-encapsulated
  • Where? underlies epithelia of GI, respiratory, reproductive and urinary tracts
  • Prepares these organs w/ pre-made plasma cells - secrete IgA as first line of defense
• Destination of plasma cells made in lymph nodes via GALT B cell activation

Question 11

2 Paths of GALT Activation

Answer 11

• IL-12 Dependent Path
  
  • 1- M cell pinocytosis of antigen
  • 2- Dendritic cell APC
  • 3- Presents to T cell
  • 4- T cell interacts w/ B cell
  • 5- B cell travels to lymph node
  • 6- In lymph node the B cell proliferates into plasma cells and memory cells
  • 7- Plasma cells —> enter circulation via diapedesis —> MALT
  • 8- Secrete antibody (IgA) to attack food
• IL-10 dependent Path
  
  • Develop tolerance to new food via regulatory T cells

Question 12

Migration Patterns of Naive T Cells v Effector T Cells v Plasma Cells

Answer 12

• Naive lymphocytes circulate through peripheral lymphoid organs, searching for foreign antigens
• Effector T lymphocytes migrate to peripheral sites of infection, where they function to eliminate infectious microbes.
• Plasma cells remain in lymphoid organs and the bone marrow, where they secrete antibodies that enter the circulation and find and eliminate microbes.