Host - Microbe Interactions

Question 1

main cells of innate immune system?

Answer 1

phagocytes

NK cells

Question 2

main cells of the acquired immune system?

Answer 2

B cells

T cells

Question 3

what do phagocytes act against?

Answer 3

bacteria

fungi

Question 4

what do T lymphocytes act against?

Answer 4

viruses
fungi
protozoa

Question 5

what do B cells and antibodies target?

Answer 5

bacteria

Question 6

what do eosinophils target?

Answer 6

worms
protozoa
fungi

Question 7

what do mast cells target?

Answer 7

worms

Question 8

what does complement target?

Answer 8

bacteria

Question 9

what features of the skin provide a physical barrier?

Answer 9

keratinocytes which secrete peptides (defensins)
sebaceous /sweat glands secrete microbe-inhibiting substances (e.g fatty acids)
antigen presenting cells in skin

Question 10

how does the mucosa of resp/GI/GU tract act as a physical barrier?

Answer 10

antimicrobial substances (e.g lysozyme)
secretory immunoglobulins A (IgA)
gastric acid

Question 11

what can cause susceptibility to infection in the lungs?

Answer 11

CF/bronchiectasis
COPD
poor swallow (e.g due to neuro problem - can cause aspiration)

Question 12

what can cause susceptibility to infection in the GI tract?

Answer 12

mucositis 2ndary to chemotherapy
IBD
bowel cancer

Question 13

what can cause susceptibility to infection in the GU tract?

Answer 13

impaired bladder emptying (e.g from benign prostatic hypertrophy)/catheterisation

Question 14

what are the 2 types of macrophages and what do they do?

Answer 14

macrophages and neutrophils

ingest organisms following opsonisation and kill via oxygen dependant or independent mechanisms

Question 15

where is phagocyte deficiency seen?

Answer 15

haematological malignancy (leukaemia, myelodysplasia)
cytotoxic chemotherapy

Question 16

what are the 2 types of T cell and what does each do?

Answer 16

helper T cells (CD4) = activate macrophages to kill microbes

cytolytic/cytotoxic T cells (CD8) = destroy infected cells containing microbes or microbial proteins

Question 17

T cell deficiency mainly causes susceptibility to what kind of organism?

Answer 17

intracellular

Question 18

what cells are mainly responsible for controlling cancer cells?

Answer 18

CD8

Question 19

where is T cell deficiency seen?

Answer 19

HIV (acquired CD4 deficiency)
lymphoma
primary immunodeficiency syndromes (e.g SCID)

Question 20

what do B cells do?

Answer 20

mature into plasma cells and produce immunoglobulins which protect against recognised antigens and help opsonise microbes for ingestion by phagocytes

Question 21

what are the first 2 antibodies produced?

Answer 21

IgM = produced first, weak affinity
IgG = produced second, strong affinity

Question 22

which antibody is the long standing, protective antibody?

Answer 22

IgG

Question 23

where is B cell deficiency seen?

Answer 23

myeloma
primary immunodeficiency syndromes (e.g CVID)
certain immune suppressants (e.g rituximab)

Question 24

how does HIV affect immunity?

Answer 24

HIV infects CD4 cells and produces progressive decline in numbers of CD4 cells resulting in deficiency in cell-mediated immunity
leads to high risk of invasive pneumococcal (strep. pneumonia) disease irrespective of CD4 count

Question 25

how does CD4 level in HIV affect susceptibility to infection?

Answer 25

normal = >450
<350 = TB, candidiasis
<200 = jirovecii, toxoplasma gondii
<100 = Cryptococcus neoformans, CMV

Question 26

what is hyposplenism and what does this cause?

Answer 26

decreased spleen function
host susceptibility to invasive infection from encapsulated organisms (strep pneumonia, H. influenza B, Neisseria meningitides)

Question 27

give 3 examples of functional hyposplenism

Answer 27

sickle cell
cirrhosis
coeliac disease

Question 28

how can risk of infection after splenectomy be reduced?

Answer 28

vaccinate before splenectomy

Question 29

how does age affect immunity?

Answer 29

elderly = more prone to infection as less able to distinguish self from non self (autoimmune disorders more common)
T cells and phagocytes respond more slowly
less complement and antibody produced
antibody binds to antigen less well

Question 30

how does immunocompromise affect immunity?

Answer 30

blunted response to stimulus
often don’t exhibit same symptoms and signs as “normal people” (i.e - no fever or localising features, no elevated CRP or neutrophilia)
often have lower threshold for treatment

Question 31

give 3 examples of immunosuppressive drugs and what infection is likely to occur?

Answer 31

steroids - fungal infections
anti TNF (infliximab/entanercept) - TB, fungal infection
purine analogues (fludarabine/cytarabine) - viral infection, pneumocystis jirovecii

Question 32

give 3 examples of prophylactic treatment

Answer 32

HIV = co-trimoxazole
bone marrow transplant = antifungal (e.g itraconazole)
splenectomy = penicillin

Question 33

how does vaccination work?

Answer 33

immunogenic antigen administered to patient
stimulates production of antibodies (IgG)
this renders immunity against organism

Question 34

are vaccinations always effective?

Answer 34

no

don’t work as well (or at all) in immunocompromised

Question 35

give 3 examples of vaccines

Answer 35

influenza
streptococcus pneumoniae (pneumococcus)
h. influenzae B/ DTP/MMR

Question 36

what happens in the immune system in sepsis?

Answer 36

disordered response to infection
inappropriate immune activation and inflammatory cascade
unchecked inflammation and cytokine storm leads to organ dysfunction

Question 37

what inflammatory mediators cause the cytokine storm?

Answer 37

IL-1
TNF alpha
IL-17

Question 38

name 7 systems which sepsis can affect?

Answer 38

cardiovascular
pulmonary
renal
liver
CNS
lactic acidosis
haematological

Question 39

hoe does sepsis affect the organ systems?

Answer 39

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