Pathogens and the Host

Question 1

Pathogen

Answer 1

organism that can cause disease

Question 2

Commensal

Answer 2

Organism that is part of normal flora

Question 3

Koch’s Postulates

Answer 3

Organism must be found in all cases of the disease

Able to be cultured outside the body for several generations

Reproduce the disease in inoculation

Question 4

Infectivity

Answer 4

Ability to become established

Question 5

Virulence

Answer 5

Ability to cause harmful effects once established

Question 6

Infectivity factors

Answer 6

Attachment (e.coli), Acid Resistance

Question 7

Virulence factors

Answer 7

Invasiveness, toxin production, evasion of immune system

Question 8

Invasiveness

Answer 8

Streptococcus Pyogenes

Question 9

Exotoxins

Answer 9

released extracellularly by the microorganism

Question 10

Enterotoxins

Answer 10

exotoxins that act on the GI TRACT

Question 11

Endotoxin

Answer 11

structurally part of the gram negative wall

lipopolysaccaride

Question 12

Tetanus

Answer 12

Exotoxin

Binds to nerve synapses. Inhibits the release of inhibitory neurotransmitters

Question 13

Cholera

Answer 13

Enterotoxin
Colonises in the small intestine
Death by dehydration

Question 14

Superantigens

Answer 14

overwhelming cytokine production causes ‘toxic shock’

divides t cells even in absence of specific antigens

Question 15

3 Virus pathogenic mechanisms

Answer 15

Cell destruction following virus infection
Virus-induced changes to cellular gene expression
Immunopathogenic disease

Question 16

Influenza A

Answer 16

Acute viral infection

virus infects cells of the respiratory tract (destruction of respiratory epithelium)

Question 17

Antigenic Drift

Answer 17

Minor changes (natural mutations) in the genes of flu viruses

Question 18

Antigenic Shift

Answer 18

Abrupt MAJOR changes in virus antigenic structure

pigs - swine flu, birds etc

Question 19

Herpes Simplex Virus

Answer 19

Latent Virus infection
1. Primary infection (activation)
STIMULUS (eg sunlight)
2. Reactivation

Question 20

Papillomaviruses

Answer 20

Cervical carcinoma

Question 21

Retroviruses

Answer 21

Lymphomas and Leukaemias

Question 22

HTLV-1

Answer 22

Human T-Lymphotropic Virus 1
Infects T cells
Modifies host gene expression using a translocating protein

Question 23

Retrovirus -induced tumours

Answer 23

Virus infects cells.
Virus nucleic acid (as DNA) integrates into cellular genome
Virus causes changes in cellular gene expression
Uncontrolled cell multiplication (TUMOUR FORMATION)

Question 24

Innate Immunity

Answer 24

Phagocytic cells - ingest foreign bodies

Question 25

Phagocytic cells (polymorphs)

Answer 25

Neutophils, eosinophils, basophils

Monocytes in blood mature into tissue macrophages

Question 26

Some organisms are resistant to…

Answer 26

Phagocytosis and intra-cellular killing

Question 27

Opsonisation

Answer 27

Organism is coated with antibody or complement - efficiency of phagocytosis is greatly improved

Question 28

Acquired Immunity

Answer 28

Specific response to antigen is concerned
Immunological memory coated
Humoral (antibody) and cellular (t cells)

Question 29

Immunoglobulin (Ig)

Answer 29

Proteins with antibody activity

Question 30

Complement

Answer 30

Combination of antibody and its specific antigen trigger the cascade of reactions

Question 31

Antibody in infections

Answer 31

Neutralises bacterial toxins

Question 32

Humoral Immunity

Answer 32

Mostly bacterial infection. Extra-cellular

Question 33

Cell mediated immunity

Answer 33

Macrophages ‘present’ antigen and stimulate T-cells.

Cytokines are produced and control the resposne

Question 34

Two main types of T cell

Answer 34

CD4 helper cells (Th1 and Th2)

CD8 suppressor and cytotoxic cells

Question 35

Th1 cells

Answer 35

activate macrophages to ingest and kill or contain pathogen

Question 36

Cytotoxic T-cells (CD8)

Answer 36

Kill infected host cells or foreign cells

Question 37

Candida Albicans

Answer 37

AIDS