Lymphatics I

Question 1

name the 2 types of T cells

Answer 1

• Helper CD4 and Cytotoxic CD8
• 6070% of circulating lymphocytes

Question 2

name the 2 types of CD4 cells

Answer 2

• CD4 helper cells (TH1 cells)
  
  • produce interleukin 2 (IL2) interferon (gamma) and tumor necrosis factor (alpha)
  • interact with CD8 cells to destroy intracellular antigens (viruses and microorganisms)
• CD4 helper cells (TH2 cells)
  
  • _​_produce IL4, IL5, IL10 and IL13
  • interact with B lymphocytes to destroy extracellular antigens

Question 3

describe B cells (bone marrow)

Answer 3

• activated B cells differentiate into plasma cells
• plasma cells secrete antibodies specific to that antigen

Question 4

describe natural killer cells

Answer 4

• attack virus-infected cells and cancer cells
  
  • causes apoptosis in cells with perforins and granzymes

Question 5

name the 2 types of immune responses

Answer 5

• innate response (non specific immunity)
  
  • occurs through action of neutrophils, macrophages, mast cells and NK cells
  • fast and nonspecific
  • does not produce memory cells
• adaptive response (specific immunity)
  
  • depends on initial recognition of antigens by B and T cells
  • slower and specific
  • produces memory cells
    
    • primary response
    • secondary response

Question 6

name the 2 types of adaptive immune response

Answer 6

• antibody mediated immunity
  
  • helper t-cells, b-cells and plasma cells
    
    • cause a release of antibodies that act on invading antigen
• cell mediated immunity
  
  • specific T cells that specialize in cytotoxicity
    
    • granzymes and perforins

Question 7

describe diffuse lymphoid tissue

Answer 7

• initial immune response
• found in lamina propria
• intercepts antigen
• no capsule
• example: MALT (mucosa associated lymphoid tissue)

Question 8

describe nodular lymphoid tissue

Answer 8

• characterized by nodules/follicles
• primary nodule: mainly consists of small lymphocytes (early child); not activated
• secondary nodule: consist of germinal center (GC): area where lymphocytes undero proliferation
  
  • paler region in GC: immaure lymphocytes (lymphoblasts)

Question 9

name the cells in a lymphatic nodule

Answer 9

• lymphocytes
  
  • B-lymphocytes
  • activated -> proliferate -> plasma cells & memory cells
• reticular cells
  
  • produce reticular fibers (stroma)
• dendritic follicular cells
  
  • most efficient APCs
  • present antigens on MHC I and II molecules
• macrophages
  
  • phagocytic and APC (contain MHC I and II molecules)
• follicular dendritic cells
  
  • dendritic in nature: lack MHC II molecules: harbors Ag-Ab complexes

FML DR

Question 10

describe the medulla of the thymus

Answer 10

• blood vessels in medulla lose ERC covering
• lymphocyte differentiate and enlarge
• mature T cells migrate into medullary blood vessels and efferent lymphatics
• ERCs contract into spherical, degenerative masses: Hassall’s corpuscle
  
  • Hassall’s corpuscles are found only in the thymic medulla and consist of rings of degenerating epithelial reticular cells

Question 11

describe DiGeorge syndrome

Answer 11

• deletion of small piece of chr. 22
• absent thymus gland is main clinical finding
• defect in the development of the 3rd and 4th branchial pouches and arches

Question 12

describe the flow of lymph in a lymph node

Answer 12

• afferent lymphatic vessels
• subcapsular (cortical) sinus
• trabecular sinus
• medullary sinus
• efferent lymphatic vessel

High endothelial venules (HEVs) in the deep cortex and medulla allow for the transition of lymphocytes from the blood stream to lymph tissue

Question 13

name the 2 cortexes in lymph nodes

Answer 13

• outer cortex
  
  • lymphatic nodules (primary and secondary) consisting of mainly B cells
  • few T lymphocytes, macrophages, reticular cells and APCs
• paracortex (deep cortex)
  
  • HEVs
    
    • allow for the transition of lymphocytes from the blood stream to lymph tissue
    • excess lymph is reabsorbed

Question 14

describe medullary cords and medullary sinuses

Answer 14

• medullary cords
  
  • branched cordlike extension of dense lymphoid tissue
  • contains primarily B lymphocytes, plasma cells, reticular cells and macrophages
• medullary sinuses
  
  • dilated spaces separating medullary cords
  • contain lymph, few wandering macrophages
  • granulocytes may be present when lymph node is draining an infected are

Question 15

contrast red pulp and white pulp in the spleen

Answer 15

• red pulp
  
  • cords of cells (cords of Billroth)
  • sinusoids (capillaries, also called venous sinuses)
• white pulp
  
  • thick accumulation of lymphocytes
  • lymphatic nodules - germinal centers that decrease with age
  • also called Malpighian corpuscles/splenic nodules