Chap 43 - Immune system Flashcards
Toll
Fungal cell wall receptors of the innate immune system in invertebrates.
Toll-like receptors (TLR)
Mammalian immune system receptors on phagocytes that detect a range of pathogens. (not just fungi)
Part of innate immune system.
Innate system cells (6)
- Neutrophils & Macrophages
- Dendritic cells
- Eosinophils
- Natural killer cells
- Mast cells
Neutrophils
Smaller phagocytic cells that travel in blood and are attracted to sites of infection.
Dendritic cells
In tissues that are in contact with the environment (eg. skin).
Stimulate adaptive immunity - very good antigen-presenting cells.
Eosinophils
Found below epithelial cells.
Deals with multicellular invaders.
Natural killer cells
Detect infected cells and activate programmed cell death.
Mast cells
Found in connective tissue. Stimulates inflammation through histamines.
Lysozyme
Enzymes that break down cell walls of pathogens.
Haemocytes
Major immune cells in Arthropods.
Phagocytic. (they dont have adaptive immune systems)
Lymphocyte
A class of white blood cell that mediates immune responses.
Natural killer cells, B cells & T cells.
Antigen
Something that binds to the receptors on B cells/T cells and thus stimulates a response.
Epitope
The small region on an antigen that binds to receptors.
Multiple antibodies can bind to different epitopes on the same antigen.
B cell receptor components
- Two identical heavy chains.
- Two identical light chains.
- Connected by disulphide bridges.
Variable (V) region
The regions on receptor chains that vary a lot between different B cells/T cells, and create binding sites for antigens.
Constant (C) region
The regions on receptor chains that are pretty much the same for all B cells/T cells, mostly it just anchors the receptor to the cells and takes care of the structure.
T cell receptor components
- An alpha and a beta chain, with binding site made of the ends of both.
- Again linked by disulphide bridges.
Major histocompatibility complex (MHC)
A complex that binds with antigen fragments within a cell, where it will then present the foreign antigen on the cell’s surface “like a bun holding a hotdog”.
T cells only bind to antigens presented on MHCs.
Effector cells (in immune system)
An ‘active’ lymphocyte that is born of a cloning B cell or T cell after its receptor is triggered by an antigen.
B cell effector form
Plasma cells that produce antibodies, short lived.
T cell effector form
Helper T cells & cytotoxic T cells.
Memory cell
A clone of a B cell or T cell that can quickly differentiate into effector cells if the same antigen is encountered again.
Primary immune response
Upon exposure to an antigen for the first time; antibodies are produced in smaller numbers and peak 10-17 days after exposure.
Secondary immune response
Upon later exposures to the same antigen; antibodies are produced faster and in larger quantities, peaking just 2-7 days after exposure.
Helper T cells
Activate adaptive immunity by stimulating B cells and cytotoxic T cells.
Need to bind to antigen from antigen-presenting cells with class II MHC.
Humoral response
Defense of cells in body fluids (“humors”) through antibodies.
Antibodies - neutralisation
Prevent virus entering cells when bound to the antigens.
Antibodies - Opsonisation
Encourage phagocytosis of a pathogen when bound onto it.
Creates a positive feedback loop - phagocytes have more antigens to present to activate more antibodies.
Complement system working with antibodies
Proteins of the complement system create pores when binding to an antibody on a pathogen.
Causes lysis of the pathogen when water/ions enter the pore.
Classes of antibodies/immunoglobin
5 classes
IgA, IgD, IgE, IgM & IgG
IgD is the one attached to the B cell membrane
Cell-mediated immune response
(as opposed to humoral response)
Killing infected cells with cytotoxic T cells.
Cytotoxic T cells
Recognises antigens in Class I MHC on infected cells.
Binds to the antigen and makes pores on the cell, leading to programmed cell death.
Active vs Passive immunisation
Active - activated response from the animal itself.
Passive - antibodies derived from another animal, such as injections of antivenom or gaining antibodies from breast milk.
Monoclonal antibodies
Antibodies that were made by a single clone and all bind to just one epitope of an antigen.
Important in modern medicine!
Rejection of transplants
Differing MHC molecules on foreign cells - there are a LOT of genes and alleles that code MHC so theres usually some variation between people.
Thymus production of lymphocytes
The thymus makes T cells.
All the T cells you have are produced in childhood!
Autoimmune vs Immunodeficiency
Its.. kinda in the name
Latency
A state of inactivity where a virus’s genome remains in a host cell but isn’t producing viral particles.
