Host Microbe Interactions Flashcards
skin: as a physical barrier
tightly packed highly keratinised cells
constant renewal and replacement
skin: physiological barriers
low pH of 5.5
low oxygen tension
skin: sebaceous glands as barriers
secrete hydrophobic oils
lysozyme that destroys the structural integrity of bacterial cell walls
ammonia has anti bacterial properties
anti-microbial peptides eg defensins secreted by keratinocytes
what are the physical defences in the mucosa of the resp/GI tract
antimicrobial substances eg lysozyme
secretory IgA
gastric acid
what bug do mast cells target
worms
how can fungal infections impair the skin barrier
eg tinea pedis
cause cracking of teh skin
what cells are phagocytes
- neutrophils and macrophages
- they are capable of engulfing bacteria and killing via oxygen in/dependent mechanisms
what bug do phagocytes target
bacteria and fungi
what are macrophages derived from
monocytes that have matured in the tissues
which bugs do T lymphocytes protect against
viruses, fungi and protozoa
helper CD4+ T cells
activate phagocytes to kill microbes
- TH1 activate macrophaes to destroy micro organisms
- TH2 activate B cells to rpoduce plasma cells which produce antibodies
effector cytokines of Th1 cells
IF gamma and IL 2
effector cytokines of TH2 cells
IL 4-6
HIV infection
- infects CD4+ T cells producing a progressive decline in their numbers
- this results in a deficinecy in cell mediated immunity
which disease is there a particularly high risk of in HIV, and how does CD4 count influence this
- invasive pneumococcal disease (S. Pneumoniae)
- irrespective of CD4
- eg bacteraemia, meningitidis, empyema etc
when is the pneumonoccal vaccine received: UK VACCINATION SCHEDULE
- 2 months
- 4 months
- withia a year of 1st birthday
- 65y
discuss the diseases that one is susceptible to with HIV, influenced by their CD4 count
- CD4 <350: TB, candidiasis
- CD4 <200: Pneumocystic jirovecii, Toxoplasma gondii
- CD4 <100: CMV
name 3 herpesviruses
CMV, HIV, EBV
what are the classical characteristics of herpesviruses
cause recurring, latent infections
CMV
- clinically very similar to glandular fever
- causes atypical pneumonia, granulomatous chorioretinitis
which viruses have a risk of feotal damage and congenital infection
toxoplasmosis and CMV
toxoplasmosis
- Protozoan parasite of cats that is transmitted to humans through undercooked meat or contact with cat litter
toxoplasmosis infection clinically
similar to glandular fever
can cause granulomatous chorioretinits, and can be sight threatening if it affects the macula
causes of hyposplenism
- splenectomy
- functional
- sickle cell disease
- cirrhosis
- coeliac
what is one particuarly susceptible to if they have hyposplenism
invasive infection from encapsulated organisms
- Streptococcus pneumoniae (pneumococcus)
- Haemophilus influenzae type B (HiB)
- Neisseria meningitidis (meningococcus)
risk can be reduced by vaccination, preferably before splenectomy etc
why are elderly people more prone to infection
- They are less able to distinguish self from non-self, and so are at a greater risk of autoimmune disease
- Phagocytes destroy bacteria and antigens more slowly
- T cells respond more slowly
- Less antibody is produced, and it binds to antigen less well
- Less complement is produced
what is the aim of immune suppression
- create a blunt immune response
- reduce damage done due to immune system as a result of autoimmunity
- to prevent transplant rejection
how does infection present in IC people
differently
- absence of fever
- lack of inflammatory response
- non specific, non localising features
immunosuppression: what can steroids cause in particular
fungal infections
immunosuppression: anti-TNF alpha therapies
can reactivate latent TB
fungal infections - particularly Aspergillus
immunosuppression: what can purine analogues cause
viral infections (HSV and VZV in particular)
pneumocystis jirovecii
what is used as prophylaxis in HIV
co-trimoxazole
what is used as prophlaxis in a bone marrow transplant
antifungal agent - itraconazole
