Host - Microbe Interactions Flashcards
main cells of innate immune system?
phagocytes
NK cells
main cells of the acquired immune system?
B cells
T cells
what do phagocytes act against?
bacteria
fungi
what do T lymphocytes act against?
viruses
fungi
protozoa
what do B cells and antibodies target?
bacteria
what do eosinophils target?
worms
protozoa
fungi
what do mast cells target?
worms
what does complement target?
bacteria
what features of the skin provide a physical barrier?
keratinocytes which secrete peptides (defensins)
sebaceous /sweat glands secrete microbe-inhibiting substances (e.g fatty acids)
antigen presenting cells in skin
how does the mucosa of resp/GI/GU tract act as a physical barrier?
antimicrobial substances (e.g lysozyme)
secretory immunoglobulins A (IgA)
gastric acid
what can cause susceptibility to infection in the lungs?
CF/bronchiectasis
COPD
poor swallow (e.g due to neuro problem - can cause aspiration)
what can cause susceptibility to infection in the GI tract?
mucositis 2ndary to chemotherapy
IBD
bowel cancer
what can cause susceptibility to infection in the GU tract?
impaired bladder emptying (e.g from benign prostatic hypertrophy)/catheterisation
what are the 2 types of macrophages and what do they do?
macrophages and neutrophils
ingest organisms following opsonisation and kill via oxygen dependant or independent mechanisms
where is phagocyte deficiency seen?
haematological malignancy (leukaemia, myelodysplasia) cytotoxic chemotherapy
what are the 2 types of T cell and what does each do?
helper T cells (CD4) = activate macrophages to kill microbes
cytolytic/cytotoxic T cells (CD8) = destroy infected cells containing microbes or microbial proteins
T cell deficiency mainly causes susceptibility to what kind of organism?
intracellular
what cells are mainly responsible for controlling cancer cells?
CD8
where is T cell deficiency seen?
HIV (acquired CD4 deficiency)
lymphoma
primary immunodeficiency syndromes (e.g SCID)
what do B cells do?
mature into plasma cells and produce immunoglobulins which protect against recognised antigens and help opsonise microbes for ingestion by phagocytes
what are the first 2 antibodies produced?
IgM = produced first, weak affinity IgG = produced second, strong affinity
which antibody is the long standing, protective antibody?
IgG
where is B cell deficiency seen?
myeloma
primary immunodeficiency syndromes (e.g CVID)
certain immune suppressants (e.g rituximab)
how does HIV affect immunity?
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
how does CD4 level in HIV affect susceptibility to infection?
normal = >450 <350 = TB, candidiasis <200 = jirovecii, toxoplasma gondii <100 = Cryptococcus neoformans, CMV
what is hyposplenism and what does this cause?
decreased spleen function
host susceptibility to invasive infection from encapsulated organisms (strep pneumonia, H. influenza B, Neisseria meningitides)
give 3 examples of functional hyposplenism
sickle cell
cirrhosis
coeliac disease
how can risk of infection after splenectomy be reduced?
vaccinate before splenectomy
how does age affect immunity?
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
how does immunocompromise affect immunity?
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
give 3 examples of immunosuppressive drugs and what infection is likely to occur?
steroids - fungal infections anti TNF (infliximab/entanercept) - TB, fungal infection purine analogues (fludarabine/cytarabine) - viral infection, pneumocystis jirovecii
give 3 examples of prophylactic treatment
HIV = co-trimoxazole
bone marrow transplant = antifungal (e.g itraconazole)
splenectomy = penicillin
how does vaccination work?
immunogenic antigen administered to patient
stimulates production of antibodies (IgG)
this renders immunity against organism
are vaccinations always effective?
no
don’t work as well (or at all) in immunocompromised
give 3 examples of vaccines
influenza
streptococcus pneumoniae (pneumococcus)
h. influenzae B/ DTP/MMR
what happens in the immune system in sepsis?
disordered response to infection
inappropriate immune activation and inflammatory cascade
unchecked inflammation and cytokine storm leads to organ dysfunction
what inflammatory mediators cause the cytokine storm?
IL-1
TNF alpha
IL-17
name 7 systems which sepsis can affect?
cardiovascular pulmonary renal liver CNS lactic acidosis haematological
hoe does sepsis affect the organ systems?
///
