Exam 3 - Immune and Lymp 1

Question 1

What is the difference between innate and acqured immunity ?

Answer 1

• Innate immunitity
  
  • lacks imune specificity and memory
  • response = inflammation
  • neutrophils are the first responders
• Acquired immunity
  
  • develops in response to antigens
  • more powerful than innate immunity
  • takes longer to develope
  • displays specficity and memory

Question 2

What is the difference b/w passive and acitve immunity?

Answer 2

• Passive immunity
  
  • temportary immunity due to donated antibodies
  • Transplacental passing of maternal antibodies to fetus
• Active immunity
  
  • permenant and long lasting immnity due to self exposure to antigen resulting in memory T cells and B cells specific for antigen

Question 3

What is the difference between primary and secondary immune tissue organs

Answer 3

• Primary
  
  • thymus and bone marrow
  • precusor cells mature into Immunocompetent cells. Each cell is program to recongize a specific antigen
• Secondary
  
  • Lymp nodes, spleen tonsils
  • Trapped antigens stilumalte clonal expansions of mature T and B cells
• L. cells mature in primary and reside in secondary
  *

Question 4

What are the characteristics of primary lymph follicles and compare with secondary lymph follicle

Answer 4

• Primary follicles (nodules)
  
  • Are spherical, tightly packed accumulation of virgin B cells and dendritic reticular cells that have not been exposed to antigens
• Secondary follicles (nodules)
  
  • are dervived from primary follicles that have been exposed to nonself antigens
  • not present at birth
    
    • Structure
      
      • corona (Cortex)
        
        • darker peripheral region
        • composed of densely packed B lymphocytes
      • Germinal center
        
        • central, lighter stained regions
        • composed of B lymphoctes, memory B cells, lpasma cells , dendritic reticular cells which function as antigen presenting cells
• Similiarlities
  
  • Are not enclosed within a capsuk
  • occur singly or in aggregates
  • Sites of B cell localization and proliferation
  • transient
• Vascular suppliy
  
  • arteriole and venule supply the cortex
  • another arteriole and venue supply center
  • lymph capillaries are not present

Question 5

What is te function of the MHC and compare the two subdivisions with the MHC?

MHC “ major histocompatibiltiy complex”

Answer 5

• Function
  
  • THe MHC gene products help present antigenic peptides to T cells
• Class
  
  • MHC 1
    
    • Expressed on the surface of all cells except trophoblast and red blood cells
    • CD8+ T cells recongized foreign proteins bount to class 1 MHC
      
      • CD8+ and T cell antigen receptor is required for MHC 1 protein fragments
  • MHC 2
    
    • expressed on the surface of B cells and antigen-presenting cells (APCs)
    • CD4+ T cells recongize peptides bound to MHC class 2 proteins on surface of APCs

Question 6

What is a CD4+ T cell?

Answer 6

• Pre-T cells develop in bone marrow
• Travel to thymus and complete maturation
• CD4 + cells
  
  • Recongize antigens bound to MHC class II molecule
  • helper cells
    
    • assist CD8+ cell differentation
    • assist B cell differentiation

Question 7

What is a CD8+ T cell?

Answer 7

• Pre-T cells develop in bone marrow
• Travel to thymus and complete maturation
• CD8 + Cells
  
  • Cytolyic T cells
  • Bind to an antigen presenting cell
  • Undergo mitosis
  • Release:
    
    • perforins
    • fas ligand
  • Recongize antigens bound to MHC class 1 molecules
  • mediators of cellular immunity

Question 8

What is a CD16+ T cell?

Answer 8

• Pre-T cells develop in bone marrow
• Travel to thymus and complete maturation
• CD 16+ Cells
  
  • Natural killer (NK) T cells
  • activated (by tumor cell antigens) T helper cells release cytokines
    
    • interleukin-2
      
      • stimultes proliferation of NK cells
    • Interferon-y
      
      • activates Nk cells
    • Macrophage activating factor (MAF)
      
      • Activates Macrophages
    • Chemotactic Factor
    • Tumor necrosis factor
      
      • killer tumor cells directly

Question 9

How do the T helper cell, macro phages, B cells and MHC complex work together in the immune response?

Answer 9

1. macrophages phagocytizes foeign material
2. foreign proteins are broken down into fragements which have antigenic properties (epitopes)
3. Antigens are expressed on surface of macrophage bound to MHC 2
4. MHC 2-Antigen Complex is is presented to helper T cell
5. ACtivted T cell undergoes mitosis
   
   1. some daughter cells become memory cells
   2. some daughter cells secrete interleukins
6. T cells attract B cells
7. B cells cells have access to free antigens
8. B cells undergo mitosis
   
   1. some daughter cells become plasma cells
      
      1. secrete appropriate antibodies
   2. Some daughter cells become memory cells

Question 10

What are the steps in the complement cascade?

Answer 10

• Compement system is an array of abour 20 serum proteins synthesized in the liver and in the blood
• classical pathway
  
  • activated by antibody binding to a pathogen
• alternating pathway
  
  • cascade directl activated by pathoen
• both facilites inFlammatory responses
• both involves coating the pathogen with complement iniating cascade

1. c1q binds to FC on Ig​
   
   1. activtes c1r
      
      1. activates c1s
         
         1. initates complement cascade
2. C1s
   
   1. C4
      
      1. C4a + C4b
3. C4 binds to surface of pathogen
4. C1s
   
   1. c2
      
      1. c2a +c2b
5. C2b binds to c4b
   
   1. c4b-c2b comlpex = c3 (convertase)
      __________________
6. C4b-C2b
   
   1. c3
      
      1. c3a and c3b
7. multiple cb3 binds to c3 convertase
   
   1. c2b-c4b-c3b complex = (c5 convertase)
8. c5 binds to c3b
   
   1. c5a + c5b
9. when c6, c7, c8, c9 are added to complex they form pores in the membrane

Question 11

What is the most important Opsonin?

Answer 11

c3b

Question 12

What are the results of the complement cascade?

Answer 12

• the activation of emmrbane attack complex (MAC) on the pathogen leading to perforations and lysis
• Production of opsonins which are coatings that make antigens more plataable to phagocytes
• release chemotactic agens (chemokines) to attach phagocytes (via chemo taxis) to areas of infection or inflammation

Question 13

WHat is the stroma?

Answer 13

• Consists mostly of rectivular fibers and cells, including undifferentiated cells and fixed and free mactophages

Question 14

What is the parenchyma

Answer 14

• consists of the cells that typicaly pack areas of the lymphoid organ
• most lymphocytes

Question 15

What are the histological features of the lymph node?

Answer 15

• Hillus
• Capsule
  
  • dense collagen fibers, some elastic, and smooth muscle fibers
• Trabeculae
• Cortex
  
  • outer
    
    • Contains lymph follicles (nodules)
  • follicles
    
    • Contains
      
      • b cells
      • follicular dendritic cells
      • migrating dendritic cells
    • secondary
      
      • mantle
      • germinal center
    • Primary
      
      • lack mantle and germinal center
  • Deep (inner)
    
    • T_h cells , macrophages
    • high endothelial venules (HEVs)
    • port of entry for cirulating differentiated lymphocytes to seed lymph node
• Medulla
  
  • irregular arrangement of loose medullary sinuses and dense medullary cords
    
    • sinuses are lined with macrophages
    • cords consists of blood vessels, lymphoblasts, and plasma cells
  • Site of lymphocyte renetry into lymph stream
  • thymic-dependent areas in subcortical and deeper medullary regions

Question 16

What is the arrangment of lymph and blood vessels in relation to the lymph node ?

Answer 16

• Hillus
  
  • Entrey and exit point for vessels
    
    • efferent lymphatic vessels, arteries, and veins enter/leave through the hilus
    • afferent ymphatic vessels, arteries, and veins enter the convex side of the node
• Capsule
  
  • dense collagen fibers, some elastic, and smooth muscle fibers
• Trabeculae
• Cortex
  
  • outer)\
  • follicles
  • Deep (inner)
• Medulla
  
  • irregular arrangement of loose medullary sinuses and dense medullary cords
    
    • sinuses are lined with macrophages
    • cords consists of blood vessels, lymphoblasts, and plasma cells
  • Site of lymphocyte renetry into lymph stream
  • thymic-dependent areas in subcortical and deeper medullary regions

Question 17

What is the sigificance of HEVs?

Answer 17

• High endothelial venules (HEVs)
  
  • Port of entry for circulating differentiated lymphocytes to seed lymph node

Question 19

What is the histological organization of the thymus?

Answer 19

• Capsule
  
  • blood vessels
  • efferent lymphatics are present
  • afferent lyphatic not present ( no lymph circulates throught the thymus)
• Trabeculae (septa)
  
  • delicate CT
  • Divide the thymus into incomplete lobules
• Lobules
  
  • Cortex (darkstaining)
    
    • epithelial reticular cells = secreation of thymosin
    • T cells in various stages of differentiation
    • thymocytes migrate from cotrical to medullary areas
    • blood vessels surrounded by continous epithelial barrier
      
      • allows thymus to maintain lymphopoiesis while segregated from antigens
  • Medulla (light staining)
    
    • Specialized to allow entry channel into blood stream of mature lymphocytes
    • capillary beds are not sheathed by epithelial cells
    • hassalls corpuscles

Question 20

What is the major characteristics of the thymus?

Answer 20

no lymph follicles (nodules)

no afferent lymph vessels

no lymph sinuses

Question 21

Where does thymosin come from?

Answer 21

Epithelial reticular cells in the cortex of lobules from the thymus

Question 22

How does the epithelial barrier relate to the surrounding blood vessels in the thymus ?

Answer 22

• LobulesCortex (darkstaining)
  
  • blood vessels surrounded by continous epithelial barrier
    
    • allows thymus to maintain lymphopoiesis while segregated from antigens
• Medulla (light staining)
  
  • capillary beds are not sheathed by epithelial cells

Question 23

What is a hassall corpuscle?

Answer 23

hassalls corpuscleswhorls of highly keratinized medullary epithelial cellsproduce cytokine thymic stromal lymphopoietin

stimulates thymic dendritic cells needed for maturation of single positive T cells

Question 24

How does a T cell change as it moves through the Thymus -> subscapular space -> outer cortex -> inner cortex -> medulla ?

Answer 24

• Double negative T cells
  
  • lack cell surface molecule of typical mature T cells
  • enters cortex form blood vessels
  • Proliferate in subscapular area
• Double positive T cells
  
  • Confronted with epithelial cells with cell surface MHC classes I and II for clonal selection
  • Express both CD4 and CD8 coreceptors and TCR receptors
• Single Postive T cells
  
  • Express TCR receptors and either CD4 and CD8 coreceptors
• Clonal deletion is completed in the medulla

Question 25

How does Foxn1 and Aire genes differentiate T cells?

Answer 25

* Foxn1 is essential for the differntiation of thymic epithelial cells. * AIre promotes expressio of a portfolio of tissue specfic cells proteins by thymic medullary epithelial cells * mutation causes autoimmune polyendocrinepathy-canidiasis-ectodermal dystrophy

Question 26

What is the difference between keratin 5+ and Keratin 18+ thymic epithelial cells

Answer 26

* Keratin 5+ * expressed by medullary thymic epithelial cells * Keratin 18+ * expressed by cortical thymic epithelial cells

Question 27

What is the structure and the components of the blood thymus barrier?

Answer 27

* located in the thymic cortex * prevents blood from contaactinf developing T cells in thymic cortex * leakyness during fetal life can cause immunological tolerance to self antigen * Componets * endothelial * endothelial basal lamina * perivascular space * basal lamina of reticular cells * reticular cells * thymic parenchymal cells

Question 28

What is the general histology of the spleen?

Answer 28

* White Pulp * Marginal Zone * Red Pulp

Question 29

What is the function of the spleen?

Question 30

How does the white pulp and the red pulp compare?

Question 31

What are PALs?

Answer 31

T cell areas surrounding the central artery near the center of the pulp forms the periarterial lymphatic sheath (PALS)

Question 32

What are Billroth cords?

Answer 32

* Billroth cords form the red pulp parenchyma * contain various blood cells, plasma cells, and antigen presenting cells * terminal capillaries open directly into substance of cord (open circulation) * Macrophages destroy worn-out or defective red blood cells

Question 33

What is the vascularization the spleen and movement of blood cells

Answer 33

* Vasculariation * splenic artery enters hilus * trabeular artieries branc off * central arieries * Adventita loosens and becomes mesh-like reticulum infiltration with lymphocytes * after cappilaries form, supplying white pulp, central artieries lose their white pulp investment and enter red pulp to form penicillus * penicillus * pulp arteriole, sheathed arteriole, and terminal capillary * ins * venous sinuses are lined with reticuloendothelial cells * drain into: * pulp veins which unite with * trabeular veins forming * splenic vein which * exits at hilus

Question 34

how do open and closed systems in the vascular drainage pattern differ?

Answer 34

* penicillus * pulp arteriole, sheathed ateriole, and terminal capillary * interceullar spaces (open system) * Venous sinuses lined with reticuloendothelial cells (closed system)

Question 36

what is white pulp

Answer 36

* White Pulp = purple after staining * assoc. w/ arteries * zones od diffuse lymphoid tissue and germinal centers * site clonal expansion and antigen stimulated lymphocytes * b cells area contains secondary follicles * T cell areas surrounding the central artery near the center of the pulp * forms the periarterial lymphatic sheath (PALS) * Reticular fibers are associated with fixed macrophages and support splenic pulp

Question 37

What is the marginal layer

Answer 37

* Forms sinusoidal interface between red pup and white pulp * abundance antigen - presenting cells * lymphocytes first encounter antigens here * activated T-helper cells activate B cells here

Question 38

What is the Red pulp?

Answer 38

* surrounds white pulp and makes up 80% of the spleen * functions to filter blood * contains large numbers of RBCs and other blood elements * Billroth cords * Vensous sinusoids

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