PBL 1 Flashcards
what is tetanus toxoid?
the tetanus vaccine
what is tetanus caused by? what does this toxin do?
an infection with the bacterium clostridium tetani
the toxin interferes with muscle contractions
When a pathogen first enters the body, what recognises it and how?
dendritic cells, mast cells and macrophages recognise the pathogen-associated molecular patterns using their pattern recognition receptors.
what do mast cells release? what is the effect?
histamine- vasodilation
cytokines- chemotaxis of macrophages and neutrophils to infection site
heparin- anticoagulant
why do mast cells secrete heparin and histamine?
as these responses allow more blood into the infected area which brings more leukocytes and can dilute toxins
when is the complement system activated? what is the importance of it?
the complement proteins in the blood are activated in the presence of a pathogen. this can enhance inflammation, opsonise the pathogen and form membrane attack complexes.
why do neutrophils come to the site of infection?what is the function of neutrophils?
chemotaxis caused by cytokines released from mast cells
release cytokines to amplify the inflammatory response, phagocytosis, degranulation and release of neutrophil extracellular traps
what do dendritic cells do when they come into contact with a pathogen?
they engulf them, break them up into epitopes and present the antigens on MHC class 2 complexes on their surface. They then move into the lymph node
What happens when a T cell comes into contact with a pathogen?
it binds to the antigen on the MHC molecule with its antigen receptor, the CD80 or CD86 molecule binds to the CD28 on the T cell and cytokines are released from the antigen presenting cell and move into the T cell. the T cell is now activated and can divide and move into the site of infection
What can cause further activation of T cells?
cytokines released from mast cells, neutrophils and epithelial cells
How can immature B cells be activated?
by attaching to free-floating antigens or coming into contact with epitopes that are presented by T cells or dendritic cells
What happens when an immature B cell attaches to an antigen or an epitope?
the B cell receptor and antigen undergo endocytosis, the antigen it proteolytically broken down and the epitope is presented on the surface by MHC class 2 proteins.
what happens to B cells once they are activated?
they undergo clonal expansion and somatic hypermutation
what is somatic hypermutation?
AID introduced point mutations to the clones and the B cells with mutations that increase the affinity to the antigen keep differentiating into plasma and memory B cells.
what do plasma and memory B cells do?
plasma B cells release antibodies that match B cell receptors
memory B cells store antibodies for future infections
