5.1. Introduction To The Immune System

Question 1

Bone marrow

Answer 1

Site of production of myeloid cells, natural killer cells & B and T lymphocytes

Question 2

Thymus

Answer 2

Immature precursors of T lymphocytes migrate from bone marrow to thymus and complete development there

Question 3

Anatomical physical barriers

Answer 3

Epithelium of skin
Alimentary tract
Respiratory tract
Urigenital tract

Question 4

Mechanical factors 
(I.e. fly swatters)

Answer 4

Associated mucous secretions and ciliated cells
Secretions of tears
Flushing action of urine

Question 5

Biochemical factors

I.e. Doom

Answer 5

Secretion of lysozyme one tears
HCl of stomach
Antimicrobial substances

Question 6

Microbial factors

Answer 6

Commensal bacteria

Other microorganisms

Question 7

Commensal bacteria

Answer 7

Own body flora (skin, stomach lining etc.)

-> pathogenic bacteria cannot get through

Question 8

Innate immune cells

Answer 8

Macrophages 
Neutrophils, 
eosinophils 
Basophils
Mast cells 
Natural killer cells

Question 9

Opsonin

Answer 9

Any molecule that enhances phagocytosis by tagging a pathogen/ microbe, or dead cells for recycling

Question 10

Mannose R

Answer 10

Receptor to mannose

Question 11

LPS R

Answer 11

Lipopolysaccharide receptor

Question 12

TLR

Answer 12

Toll like receptor

Question 13

FcR

Answer 13

Receptor to Fc (constant region) portion of antibody

Question 14

NLR

Answer 14

1. Nod-like receptor
2. Recognizes molecules released by damaged cells
   E.g. ATP

Question 15

PAMPS

Answer 15

Pathogen molecular patterns on microbes

E.g. LPS (receptors are Toll like receptors: TLRs)

Question 16

DAMPs

Answer 16

Damage associated molecular patterns

E.g. uric acid, ATP (receptors are NOD like receptors: NLRs)

Question 17

CR

Answer 17

Complement receptor

- CR recognizes 3b on surface

Question 18

Phagocytes

Answer 18

Cells that protect the body by ingesting (phagocytosing) harmful foreign particles, bacteria, and dead or dying cells

Question 19

Phagolysosome

Answer 19

Phagosome fuses with lysosome

Question 20

Oxygen dependent

Answer 20

(Respiratory burst)

1. NADPH oxidase in phagolysosome membrane converts O2 into superoxide O2
2. This is converted into hydrogen peroxide by superoxide dismutase (SOD)
3. Myeloperoxidase and chloride produce hypochlorite (HOCl)

Question 21

Oxygen independent

Answer 21

(Enzymes & toxic molecules)

1. Lysozyme, nucleases & proteases degrade pathogens/ antigens

Question 22

Process of phagocytosis

Answer 22

1. Phagocyte adheres to pathogens or debris
2. Phagocyte forms pseudopods that eventually engulf the particles, forming a phagosome
3. Lysosome fuses with the phagocytic vesicle, forming a phagolysosome
4. Lysosomal enzymes digest the particles, leaving a residual body
5. Exocytosis of the vesicle removes indigestible & residual material

Question 23

Humoral component

Answer 23

Complement acute phase proteins

Question 24

Complement

Answer 24

1. A group of proteins that are produced by the liver & circulate i. The blood
   - numbered in the sequence that they were discovered e.g. C1, C2
2. Infection activates complement pathways that cut complement proteins into fragments
   - act as chemo-attractants e.g. C3a, C5a
   - opsonins e.g. C3b
   - forms the membrane attack complex (MAC) (C5b678 and multiple 9) which forms a pore in the pathogen/ microbe wall and lyses the cell

Question 25

Acute phase proteins

Answer 25

Proteins made by liver in response to activated macrophages and neutrophils - CRP - MBL

Question 26

CRP

Answer 26

C reactive protein

Question 27

MBL

Answer 27

Mannose binding lectin

Question 28

Adaptive immune response

Answer 28

1. This is the response of lymphocytes each with its own unique receptor that are specific for either a peptide associated with a MHC protein (T cell) or epitope on the pathogen/ microbe (B cell) 2. Consists of: - B lymphocytes - T lymphocytes 3. Selection of antigen-specific lymphocytes occurs - only fe lymphocytes will have receptors that specifically recognize the peptides from pathogens/ microbes presented on MHC or epitope on exterior surface of pathogen/ microbe 4. Now these lymphocytes need to proliferate to produce a clone 5. Hence the adaptive response is delayed 6. Memory cells are produced that give an immediate and stronger response to a second exposure to pathogen/ microbe

Question 29

B lymphocytes

Answer 29

Have B cell receptors (BCR)

Question 30

T lymphocytes

Answer 30

Have T cell receptor (TCT)

Question 31

Lymph nodes

Answer 31

Excess extra cellular fluid with pathogen/ microbe from ECM drains to it and dendritic cells carry engulfed pathogen/ microbe to it and there meet circulating naive lymphocytes - monotreneal tissues

Question 32

Spleen

Answer 32

Pathogens/ microbes present in blood are trapped here by resident macrophages and dendritic cells and they activate naive lymphocytes entering via blood vessels

Question 33

MALT

Answer 33

- mucosa associated lymphoid tissue 1. Pathogens/ microbe entering through mucosa are engulfed by resident dendritic cells which then activate naive lymphocytes in the mucosa - tonsils - Peyers patches - appendix

Question 34

Naive B cells

Answer 34

Activated by binding of microbe/ pathogen to BCR

Question 35

Effector CD4 T cells

Answer 35

Further activate naive B cells

Question 36

Antibodies

Answer 36

1. Secreted BCR 2. Bind to specific epitope on its antigen: Pathogen/ microbe 3. Different classes have different constant regions which determine their function 4. Act as opsonin or activate classical complement pathway

Question 37

TCR-CD8 T cells

Answer 37

Cytotoxic

Question 38

TCR-CD4 T cells

Answer 38

Helper

Question 39

Adaptive immune response: T cells

Answer 39

1. Each T lymphocyte has its own unique TCR made from rearranges gene segments 2. They have a co-receptor CD4 or CD8 3. The CD8 T cells are the cytotoxic T cells 4. The CD4 T cells are divided up into helper and regulatory T cells

Question 40

Naive T cells

Answer 40

Activated by dendritic cells in secondary lymph organs to become effector T cells

Question 41

Effector T cells

Answer 41

Perform the cellular functions of the adaptive immune response: 1. CD8 T cells kill infected body cells 2. CD4 T cells - activate dendritic cells to activate CD8 T cells more efficiently - activate macrophages to be better killers - activate B cells to become plasma cells and secrete antibodies

Question 42

Immunological synapse

Answer 42

1. Cell to cell interaction between body cells or antigen presenting cells, and T cells 2. This is how naive CD8 and CD4 T cells are activated by dendritic cells 3. This is how effector CD8 T cells recognize the cell to kill 4. This is how CD4 T cells activate macrophages, dendritic cells, and B cells to become plasma cells