Flashcards in Infection Deck (188)
What are the causative organisms of enteric fever?
Salmonella enterica typhi
Salmonella enterica paratyphi
How are Salmonella enterica typhi/paratyphi spread?
How can you reduce your risk?
Hand hygiene, safe food, vaccination
What treatments are effective in enteric fever?
Signs and symptoms of enteric fever
Constipation or diarrheoa
Intestinal haemorrhage and perforation
Investigations in suspected enteric fever
Stool and blood cultures
How do salmonella enterica typhi/paratyphi cause illness?
Fibriae adhere to epithelium over peyers patches
Invasin allows intracellular growth
As gram -ve have endotoxins
How can salmonella enterica typhi/paratyphi be distinguished in culture from escherichia coli?
They. Are non lactose fermenters
Otherwis both gram neg aerobic bacilli
What travel related infection is present in southern Europe?what is the causative organism?
How does brucellosis spread?
Spread via breaks in the skin and via the. Gi tract (e.g. Unpasturised milk)
Very rare person to person direct contact spread
How does brucellosis present?
Non specific flu like febrile illness
Bone and joint involvement
Long term complication endocarditis
How is brucellosis treated?
What are the two main components of adaptive immunity?
How is mhc adapted to a generalist presenting role?
Co dominant expression giving range of different subgroups
Peptide binding clefts very polymorphic
What is the difference in structure of mhc class 1 and class 2?
Class one - three alpha and one beta units
Class two - two alpha and two beta units
Note that the alpha and beta units are located on separate polypeptide chains.
What mhc molecule is active in cellular immunity? Which in humoural immunity?
Cellular - mhc 1 on most cells, both on apcs
Humoural - mhc 2 on apcs
How are cytotoxic t cells activated?
CD8 binds to MHC1 on an antigen presenting cell - presenting antigen recognised by t cell receptor
T cell binds to antigen on MHC1 on infected cell
Costimulation from IL2 produced by activated CD4 TH1 t cells
How do activated cd8 t cells kill the cell?
Release granzymes (protein digesting enzymes that trigger apoptosis)
Release granulysin and perforin (create channels in plasma membrane)
How does a t cell bind to a antigen presenting cell?
CD4/8 recognises MHC2/1. T cell receptor detects antigen in the MHC
How is an antigen attached to MHC1?
Sampling of cytosol
Proteins broken down by proteasome
Fragments released into ER
Fragment attached to MHC1
MHC1 moves to cell surface
How is an antigen attached to MHC2?
Pathogen phagocytosed by APC
Pathogen broken down by low pH and proteolysis
Vesicle of fragments merges with vesicle containing MHC2
Fragments load onto MHC2 and are moved to cell membrane
How are cd4 t cells activated?
Recognise and bind MHC2 on APC
Co stimulated by IL2 from APC
What do activated CD4 T cells do once activated?
TH1 - release IL 2 costimulating CD8 cells
TH2- costimulate b cells causing them to differentiate into plasma cells. Also activates eosinophils and mast cells
TH17 - activate neutrophils
What are the different antibodies?
What do they do?
G - opsinisation
A - mucosal immunity decreasing aggregation
M - initial response to novel antigen
E - on mast and basophils involved in allergic reaction/parasites
D - B cell receptor
What are the main functions of antibodies
Enhancing phagocytosis by opsionisation
Neutralisation of toxins
Complement activation (classical pathway)
In an infection what is the first antibody released? What is released on reinfection? What is different?
IgG much faster stronger and longer with a higher affinity
What are clinical uses of antibodies?
Active immunisations (e.g. Rabies)
Immediate protection (e.g. Post exposure hep b)
What would make a hiv patient a slow progressor?
MHC configured to present antigens of the virus that cannot be altered by the virus, thus the virus cant mutate and avoid being expressed.
What is the difference between HLA and MHC
MHC is the protein
HLA is the locus on the genome
How can HIV be subclassified generally? What is the epidemiology?
Hiv 1 - most common, nearly all western cases
Hiv 2 - confined to west africa, more indolent course