Immunity & Infection

Question 1

Effector Lymphocytes

Answer 1

1. B Lymphocytes - Antibody production
2. CD8 T lymphocytes - Antigen specific cytotoxicity
3. NK lymphocytes - Natural killer
4. K Lymphocytes - ADCC

Question 2

Regulatory lymphocytes

Answer 2

1. CD4 T helper lymphocytes - Cytokine production
   a) TH1 - Intracellular (bacteria and viruses)
   b) TH2 - Multicellular (parasites and allergy)
2. Regulatory T cells - Down regulation
3. TH17 - Mucosa and inflammation

Question 3

Factors relating to the micro-organism causing infection?

Answer 3

1. Type of micro-organism
2. Dose
3. Virulence factors
4. Route of entry

Question 4

Host factors that cause infection?

Answer 4

1. Integrity of innate barrier
2. Competency of specific immune system
3. Genetic capacity (e.g. HLA, Ig’s)
4. Previous exposure to infection
5. Co-infection

Question 5

Factors of viruses recognized by host?

Answer 5

Capsid antigens

Internal metabolites and structures presented on HLA 1

Question 6

Factors of bacteria recognized by host?

Answer 6

Extracellular structural components

Toxins and metabolic products

Question 7

Factors of parasites recognized by host?

Answer 7

Multi-cellular organisms that undergo rapid life cycle changes which also change antigenicity.

Question 8

Function of antibodies

Answer 8

Direct neutralization
Promote’s opsonisation (via Fc region)
Complement mediated effects

Question 9

What are antibodies effective against?

Answer 9

Viruses (IgA, IgG, IgM)
Extracellular bacteria (IgG, IgM, IgA)
Toxins (IgG, IgM)
Parasites (IgE, IgA)

Question 10

What are CD8 cells effective against?

Answer 10

Virus infected cells
Tumor cells
Transplanted organs

Question 11

Methods bacteria use to avoid antibody effects

Answer 11

Intracellular - TB

Sugar capsule to prevent opsonisation - Haemophilus influenza

Question 12

Mucosal immunity

Answer 12

IgA in mucosal epithelium that are specific for pathogen will bind and prevent adherence and promote opsonisation.

If bacteria does invade, there are IgE antibodies in submucosa that will bind to the pathogen. MAST cells will recognize Fc region of IgE antibodies which will causes degranulation.

Granules stimulate vasoactive and chemo-tactic factors which bring in IgG, complement, neutrophils and eosinophils.

Question 13

Receptors on NK/K lymphocytes?

Answer 13

Fc(gamma) receptor (CD16) - Natural killer effect

Killer activating and killer inhibitory receptors

Question 14

How do Natural Killer cells work

Answer 14

Killer activating and killer inhibitory receptors bind to ubiquitous receptors and HLA 1 receptors on normal cells.

When a cell is infected by a virus or has a tumor, HLA 1 is down-regulated in that cell. Killer inhibitory cells bind less to HLA 1 molecules and stimulates NK cell action via degranulation,

Question 15

What cytokines stimulate NK cell activity?

Answer 15

IL-2 and IF-γ

Question 16

Where are NK cells mostly used

Answer 16

EARLY in viral infections and tumors.

Question 17

Contributors to acute viral infection

Answer 17

1. Interferon’s - Non-specific cytokines produced by viral infected cells to a) Pass on non-specific transient viral resistance to surrounding cells and b) Stimulate natural killer cells.
2. Natural killer cells - Stimulated by IFN-gamma. Stimulated by the down regulation of HLA-1 molecules on infected cells. And kill them.
3. Cytotoxic T cells - Recognize peptides presented on HLA-1 receptors on infected cell.
4. Antibody production ready for re-infection.

Question 18

What are the pro-inflammatory cytokines

Answer 18

IL-1, IL-6, TNF-alpha

Question 19

Chemokines

Answer 19

Chemotactic factors. Direct effector cells.

Question 20

Interferon’s

Answer 20

Acute anti-viral response
Transient viral resistance
NK stimulation
Up-regulate MHC - 1 receptors for cytotoxic T cells.

Question 21

Role of IL-1.

Answer 21

Mediates defense against bacteria

Temperature regulation

Question 22

Role of TNF-alpha

Answer 22

Mediates defense against bacteria
Tumor necrosis
Temperature regulation

Question 23

Role of IL-6

Answer 23

Stimulation of acute phase proteins.