Immune System 1

Question 1

What is an immunogen?

Answer 1

• a molecule that stimulates the immune
  system to produce a response

Question 2

What is an epitope ?

Answer 2

• part of antigen that reacts with immune effector cells or soluble antibodies

Question 3

What are the 4 main types of pathogen?

Answer 3

• Bacteria
• Viruses
• Fungi
• Parasites i.e warms

Question 4

What is a common lymphoid progenitor ?

Answer 4

• Derived from hematopoietic stem cell in bone marrow
• differentiates into T, B, NK lymphocytes

Question 5

What is a common myeloid progenitor ?

Answer 5

• Derived from hematopoietic stem cells in bone marrow
• produces granulocyte and megakaryocyte

Question 6

Primary lymphoid organs

Answer 6

• Bone marrow
• Thymus

Question 7

Secondary lymphoid organs

Answer 7

• Spleen
• Adenoids
• Tonsils
• Appendix
• Lymph nodes

Question 8

what are the 2 types of immunity ?

Answer 8

1. Innate Immunity:
   - Rapid response, no memory, fixed specificity.
2. Adaptive Immunity:
   - Slow response, memory formation, highly specific.

Question 9

what are the 2 kinds of innate immune response ?

Answer 9

• immediate
• induced

Question 10

what are 3 features of the immediate innate immune response ?

Answer 10

1. Barriers: Skin, mucous membranes.
2. Peptides: Destroy microbes directly.
3. Complement System:

Question 11

what is an antigen ?

Answer 11

• part of the immunogen that reacts with immune effector cells or soluble anti-bodies

Question 12

What are the 3 classifications of myeloid cells?

Answer 12

1) Granulocytes
- Neutrophil
- Eosinophil
- Basophil

2) Antigen presenting cells
- monocytes
- macrophages
- dendritic cells

3) Mast cells

Question 13

what are the 3 types of APC’s ?

Answer 13

• monocytes
• macrophages
• dendritic cells

Question 14

what are the 2 classifications of lymphoid cells ?

Answer 14

1) Small lymphocytes
- B cells
- Tcells

2) Large lymphocytes
- NK cells

Question 15

function of bone marrow?

Answer 15

• B cells originate + mature
• T cells originate + leave at immature stage

Question 16

function of thymus ?

Answer 16

• located above the heart
• immature T cells migrate to complete maturation

Question 17

what is the key difference between primary and secondary lymphoid tissues ?

Answer 17

• primary = lymphocytes are only produced and mature
• so new immune response takes place - only in secondary
• secondary = activation of lymphocytes

Question 18

what are the 3 types of secondary lymphoid tissues + functions ?

Answer 18

1)Lymphatic Vessels - transport lymph

2) Lymph Nodes - filter lymph

3) MALT (Mucosa Associated Lymphoid Tissue) - specialised tissue in submucosal layers of GI, respiratory, urinary tracts
eg. adenoids, tonsils , appendix, peyer’s patches

Question 19

How do lymphocytes respond to infection in the lymph nodes?

Answer 19

• pathogens are carried to lymph nodes through afferent lymphatic vessels
• where they are trapped by dendritic cells and macrophages
• B and T cells ‘meet’ the pathogens
  -become activated and undergo clonal expansion.
• As lymphocytes proliferate, the lymph node increases in size, leading to swollen glands

Question 20

cells in innate vs adaptive immunity

Answer 20

• innate = NK cells, neutrophil, basophil, eosinophil, monocyte
• adaptive = B cell, T cell
• both = macrophages + dendritic cells

Question 21

what is the complement system + and what is its role in immunity?

Answer 21

• Group of nearly 30 serum and membrane proteins.
• Act in an orderly sequence.
• Initial activation leads to a highly regulated enzymatic cascade.
  Roles:
• Activated proteins bind covalently to bacteria (acting as opsonins).
• Opsonized bacteria are phagocytosed by immune cells with complement receptors.

Question 22

Classical pathway of complement system

Answer 22

• Antibody-dependent and antibody-independent activation.
• C4b acts as an opsonin, enhancing phagocytosis.

Question 23

Alternative pathway of complement system

Answer 23

• Can be activated independently or dependent on the classical pathway.
• C3b acts as an opsonin for phagocytosis.
• C3a/C5a are pro-inflammatory molecules, promoting inflammation.
• MAC (Membrane Attack Complex): causes lysis of pathogen

Question 24

what does MAC do ?

Answer 24

• causes Lysis of pathogen

Question 25

What are the main phagocytic cells, and their key features?

Answer 25

Neutrophils: - Short-lived cells. - Multi-lobed nucleus - Abundant at sites of acute inflammation. Mononuclear phagocytes (Monocytes and Macrophages): - Include blood monocytes, alveolar macrophages, etc. - Longer-lived cells. - Function as Antigen Presenting Cells (APCs).

Question 26

process of phagocytosis

Answer 26

1) Recognition and Attachment - Receptors on phagocytes bind to microbes. - Opsonin receptors: Phagocytosis is enhanced when microbes are coated with opsonins (like C3b and C4b) 2)Engulfment: - The phagocyte's plasma membrane surrounds the microbe, forming a phagosome. - The phagosome then fuses with a lysosomal granule to form phagolysosome 3)Killing and Degradation: - The lysosomal enzymes (e.g., elastase, lysozyme) within the phagosome kill and degrade the engulfed pathogen.

Question 27

What are cytokines ?

Answer 27

- low molecular weight proteins (5-25 kDa) secreted by cells to regulate the activity, proliferation, or differentiation of other cells - types of cytokines = interleukins, chemokines, lymphokines

Question 28

3 role of cytokines in immune response ?

Answer 28

1. Mediators and Regulators of Innate Immunity: - Produced mainly by mononuclear phagocytes (e.g.macrophages) + neutrophils in response to infectious agents. 2. Mediators and Regulators of Adaptive Immunity: - Produced mainly by T lymphocytes in response to specific recognition of foreign antigens. 3. Stimulators of Hematopoiesis: - Produced by bone marrow stromal cells, leukocytes, and other cells to stimulate the growth and differentiation of immature leukocytes.

Question 29

What are some cytokines produced by macrophages and their effects?

Answer 29

- IL-1, IL-6, TNF (Tumor Necrosis Factor) - IL-1, IL-6, and TNF help induce fever, which inhibits bacterial and viral replication by raising the body temperature. - induce a state of inflammation

Question 30

what are the features of inflammation ?

Answer 30

- vasodilation - increased vascular permeability - leukocyte migration - aim to bring immune cells to location of infection

Question 31

induced innate immune response ?

Answer 31

- phagocytosis - cytokines - toll like receptor activation - Nk cells