Lecture 2: Overview of Immune System

Question 1

Describe the general features of innate immunity.

Answer 1

• It is the first line of defence that produces a rapid response
• Calls for reinforcements (including the stimulation of the adaptive immune response)
• (Usually) not associated with generating memory
• Relatively non-specific: recognises pathogen-associated molecular patterns (PAMPs)

Question 2

Mention the components and effector functions of the innate immunity.

Answer 2

Components:

• physical barriers (skin, mucus)
• soluble proteins (complement, cytokines, chemokines)
• cells (macrophages, granulocytes)

Major effector functions:

• phagocytosis “to eat”
• secretion of proteins (cytokines, chemokines, complement)
• cytotoxicity

Question 3

PAMPs recognition allows _____________, ______________________, and _______________________.

Answer 3

phagocytosis, cytokine production, antigen presentation

Question 4

Describe phagocytosis.

Answer 4

Pathogens or infected cells can be engulfed by phagocytic cells, transported to lysosomes/phagolysosomes and be degraded by proteases and other enzymes.

Question 5

Cytokine production signals _________________.

Answer 5

recruitment of other inflammatory cells

Question 6

How is the adaptive immune response initiated?

Answer 6

If the innate immune response fails to remove the infectious agent, the response progresses first by the transport of the foreign antigen by antigen-presenting cells (dendritic cells) migration to secondary lymphoid organs, where it will initiate the adaptive immune system.

Question 7

Describe the general features of adaptive immunity.

Answer 7

• Specificity
  
  • ability to discriminate between different molecular entities and respond uniquely
• Adaptiveness
  
  • Ability to respond to previously unseen molecules
• Discrimination between self or non-self
  
  • ability to recognise foreign molecules and to avoid responding to self
• Memory
  
  • ability to recall previous contact and respond with a larger and more rapid response

Question 8

Mention the components and effector functions of the adaptive immunity.

Answer 8

• Components:
  
  • lymphocytes: B cells, T cells
  • soluble proteins (cytokines, antibodies)
• Major effector functions:
  
  • Production of antibodies to opsonise bacteria. neutralise viruses and toxins, sensitise mast cells, activate complement
  • provide assistance for efficient B cell, macrophage, and CD8+ T cell function
  • cytoxicity to infected/transformed cells

Question 9

Lymphocytes originate in the ___________

Answer 9

Bone Marrow

Question 10

Describe the role of the primary and secondary lymphoid organ

Answer 10

• Primary Lymphoid Organs
  
  • development and maturation of lymphocytes
  • bone marrow (B cells) and thymus (T cells)
• Secondary lymphoid organs
  
  • Lymphocytes encounter pathogens and undergo clonal selection
  • Spleen, lymph nodes, tonsils, Peyer’s patches, appendix

Question 11

Recall the life of a B cell lymphocyte.

Answer 11

Question 12

Recall the life of a T cell lymphocyte.

Answer 12

Question 13

Mention the basic mechanisms behind lymphocyte receptor rearrangement,

Answer 13

• Combinatorial diversity
  
  • Gene rearrangement that combines different combinations of gene segments to form a complete V region exon
• Somatic recombination
  
  • DNA recombination cutting and splicing arrays of V, D, J segments
• Junctional diversity
  
  • Additional/deletion of additional nucleotides in the formation of junctions between gene segments

Question 14

Describe briefly regarding the lymphocyte central regulation.

Answer 14

For B cell, those that have a reaction with self-antigen is retained in the bone marrow.

For T cell. first occurs a positive selection by the cortical epithelial cells in the thymus, where cells that can’t recognize MHC molecules are selected to die.

Then, it undergoes negative selection where cells that bind strongly to self-MHC are selected to die

Question 15

Describe the process of proliferation and clonal selection.

Answer 15

Question 16

Mention the B cell antibody functions.

Answer 16

Question 17

Describe how T cells recognize antigens.

Answer 17

Question 18

________________ pick up antigen and migrate to the lymph nodes.

Answer 18

Dendritic cells

Question 19

Differ between MHC I and MHC II.

Answer 19

MHC I: expressed on all nucleated cells

MHC II: expressed on antigen-presenting cells (dendritic, macrophages, B cell)

Question 21

Mention what is required for the effective activation of naive T cells.

Answer 21

The antigen-presenting cell must:

1. acquire and process antigen in compartments which gain access to MHC Class I and Class II pathways
2. Interact with naïve T cells to induce effector T cells

• Locate appropriate T cells (in the secondary lymphoid tissue)
• Adhere to T cells
• Present MHC associated peptides to T cells (Signal 1)
• Provide “co-stimulation” (Signal 2) for T cell expansion
• Induce T cell differentiation (Signal 3)

Question 22

Mention some examples of T cell functions.

Answer 22

Question 23

Describe the concept of immune memory

Answer 23

A small number of effector cells gain immunological memory and these are able to produce stronger and faster responses on subsequent encounters with the pathogen (secondary response)

Question 24

What are the primary lymphoid organs?

Answer 24

Thymus and Bone Marrow