Topic 15 - Humoral immunity, B lymphocytes and self restriction

Question 1

Words to include in humoral immunity

Answer 1

• Specific immune response (acqired)
• Humoral immunity
• Cellular immunity
• Antibodies
• Immunoglobulin
• Ligansa
• Heterogenic
• B-lymphocytes
• Antigen
• B-cell maturation:
  
  1. Prepratory phase
     
     • Antigen dependent
     • Pre-B-lymphocytes
     • Virgin-B-lymphocytes
     • IgG-like molecule
     • Primary lymphatic organs
       
       • Hemopoetic stem cells
       • Bursa equivalent
         
         • Fetal liver
         • Adult bone marrow
  2. Antigen independent phase
     
     • APC presented Ag
     • Virgin-lymphocyte
     • Th-independent
     • Th-dependent
     • Interleukins (IL-1, IL2, IL4)
     • Circulation
     • B-dependent zones
     • Secondary lymphatic organs
     • Blastic tranformation
     • Plasma cells
• Immune response
• Antigen-binding receptor (antibody molecules)
• Antigen epitope
• Plasma cells
• Memory cells
• Primary response
  
  • Antibody production
• B-cell
• T-cell
• Membrane receptor
• Endocytosis
• Epitopes
• MHC class II protein
• Helper T-cells
• Cytokines

Question 2

Words to include in B-lymphocytes

Answer 2

• Bone marrow
• Antigen
• Plasama cells
• Memory B-cells
• Immune cells
• Antibody production
• Membrane surface:
  
  • Immunoglobulin-like structure
  • Receptors
• Migration
• Phagocytosis (ø)
• Tissues (ø cornea and heart valve)
• Lymphopenia
• Lymphocytosis
• Immunoglobulins

Question 3

Words to include in self restriction

Answer 3

• Ag stimulus
• Immune response
• Lys
• Memory cell
• Lymphokines
• FcRs
• Feedback

Question 4

What are the major forms of specific immune response

Answer 4

1. Humoral immunity
2. Cellular immunity

Question 5

Production of antibodies

Answer 5

• Synthesized by B-lymphocytes
• Antigen specifically activates the B-cells which will produce immunoglobulins (antibody)
• B-lymphocytes recognize and produce antibodies at different phases of their maturation
• B-lymphocytes with cell surface immunoglobulins are called “recognizing cells”, and they bind to an antigen
  
  • Antigen binding triggers the cell differentiation leading to the transformation of B-lymphocytes to plasma cells
  • Plasma cells are secreting antibodies

Question 6

Development of humoral acquired immunity

Answer 6

• B-cell maturation

1. Antigen independent phase
   
   • Preparatory phase
   • Pre-B-lymphocytes mature and become virgin-B-lymphocytes
   • On the surface of each virgin-B-lymphocyte the ara an IgG-like molecule
   • Location: bone marrow (primary lymphatic organs)
2. Antigen dependent phase
   
   • ​B-cell activation
   • If there is an APC presented Ag against which the virgin B-Lymphocyte has an Ig structure
   • Virgin-lymphocyte bind the antigen and it gets acitvated
     
     • Activation can be Th-independent or Th-dependent
     • Inteleukins (cell signals) activate the B-lymphocyte
     • Activated B-lymphocyte can settle in the B-dependent zones of the secondary lymphatic organs, where it goes through blastic transformation

Question 7

Immune response

Answer 7

• The antigen-binding receptors located in the cell membrane of the B-lymphocytes are antibody molecules
• When an antigen enters the body it is recognized by B-lymphocytes containing the proper antigen-binding receptor
• The activated lymphocytes within this clone then begin to divide rapidly
• The daughter cells differentiate into two directions and become plasma cells or memory cell
  
  • Plasma cells: die after a few days of intensive antibody production, since the antibodies are proteins
  • Memory cells: Do not participate in the immediate attack on the antigen, but continue to live for months and years after the antigen has been eliminated, ready for stimulation if the antigen is encountered again

1. Primary response
   
   • First exposure to an antige
   • Several days before formation of antibodies begin
2. Secondary response
   
   • Memory cells, will be present due the the previous attack
   • The memory cells produce a large amount of antibodies
   • Faster than primary response

• For further activation to occur the B-cell needs help of a T-cell, as antigens must be recognized by a T-cell
• The complex formed between the antigen and the membrane receptors of the B-cells is transported into the cell (endocytosis) broken down to antigenic epitopes carried back to the surface of the cell, with the B- cell’s MHC class II proteins
• The antigen will be recognized by helper T-cells, which bind to this complex
• Activated helper T-cells produce cytokines that stimulates the B-cell to divide and differentiate into plasma cell

Question 8

Self restriction

Answer 8

• After Ag stimulus, the efficiency and potency of the immune response will decrease due to:
  
  • Elimination of Ags, which reduces the Ag stimulus
  • The activated Lys will die or converted to memory cell
  • The immune response generates several costimulatory mechanisms (interactions of different membrane structures), lymphokines, FcRs, etc., which influence the immune response negatively or positively (feedback)