IM1: Cells of the immune system Flashcards
What are the 3 types of granulocytes
- Neutrophils
- Eosinophils
- Basophils
What are the functions of neutrophils
Most numerous, phagocytose and ingest bacteria
What are the functions of eosinophils
Defence against parasites and involved in allergic reaction
What are the functions of basophils
Defence against parasites and involved in allergic reaction
What are the functions of mast cells
Mediate allergic reactions through release of histamine
What are the functions of macrophages
Found in bloodstream for phagocytosis and antigen presentation
What are the functions of dendritic cells
Responsible for phagocytic antigen uptake and presentation to T-cells
What are the functions of NK cells
Natural killer cells kill cells infected with intracellular pathogens by releasing lytic granules
What are the functions of B cells
- present antigens to T-cells
- produce antibodies
What are the three functions of antibodies
- Neutralisation; surround pathogen and prevent adherence to cells
- Opsonisation; coat pathogen for marking to promote phagocytosis
- Complement activation; enhance opsonisation and lysis of bacteria
How are antibodies expressed
- B-cell receptor = BCR on the surface
- B cells secrete antibodies to diffuse and bind
The antigen is initially recognised by BCR and then activates B cells to secrete antibodies specific to the bacterium
What is IgM important for
Complement activation
What is IgG important for
Neutralisation, opsonisation and complement activation
What is IgA important for
Neutralisation in the GIT
What is IgE important for
Activating mast cells in parasitic and allergic responses
What is IgD important for
This is the B-cell receptor
What is the role of CD8+ T cells
Recognising and removing virus infected cells and cancer cells (CTLs = cytotoxic lymphocytes) they have granules containing cytotoxins causing apoptosis
They are tightly regulated due to their high potency
What is the importance of TH1 cells
Coordinating immune responses against intracellular microbes (esp. bacteria) by producing and secreting molecules that alert and activate other immune cells
What is the importance of TH2 cells
Coordinate immune responses against extracellular pathogens by alerting B cells, granulocytes and mast cells
What is the importance of TH17 cells
Produce IL-17 which activates immune and non-immune cells and is important for neutrophil recruitment
What is the importance of T-regs
Prevent adverse immune activation and prevent immune response against self cells
What do type I interferons mediate
Antiviral immune response
What do type II interferons mediate
Antibacterial response
What do interleukins do
Provide instructions with activator or inhibitor responses
What is the role of tumour necrosis factor
Stimulates immune-cell proliferation and activation and are important in inflammatory resoisnes; TNF blockers are used to treat autoimmune disease
What is the role of toll like receptors
Recognise general microbial patterns and are essential for innate immune-cell activation and inflammatory responses
What are B-cell receptors
These are found on the cell surface and are also secreted as antibodies to neutralise pathogens
What is the role of major histocompatibility complex (MHC)
MHC proteins are carriers for presenting antigens on cell surfaces
What do MHC class I proteins do
Present viral antigens which will be recognised by CD8+ T cells which will recognise and kill the infected cells
What do MHC class II proteins do
Only expressed by APC’s (dendritic cells and macrophages) and present antigens to CD4+ T cells
