Adaptive immunity Flashcards
What is an acquired immune response?
- Recognition of foreign material or ‘antigen’, also causes T-cells to proliferate.
- This is turn causes B cells to proliferate. (Clonal expansion)
What is humoral immunity?
- B-cells responding to antigens
- Called humoral immunity because it was located in the body’s humors or fluids
What is cell-mediated immunity?
- T-cells responding to antigens
- Called cell-mediated immunity because it relates to protection coming from the blood
What are serum proteins called?
-Serum proteins are called globulins and they are named by their solubility in assay
What are immunoglobulins secreted by?
-Immunoglobulins are secreted by B lymphocytes and are called antibodies
What do cell-mediated responses involve?Fc
- Cell mediated responses involve receptors bound to the surface of the T-lymphocyte
- They come from T-lympocytes and T-cell receptors
Variable regions in antibodies and T-cell receptors bind antigen
Antibodies and TCRs have:
-Variable regions (V)
-Constant (C) regions
Variable regions bind antigens
What are Fc receptors?
- The constant region of the antibody binds to receptors within the immune system.
- These are called Fc receptors.
- There are different types of Fc receptor and the nature of the Fc receptor bound by the antibody determines how the antibody works within the immune system.
Immunoglobulin G
-IgG is secreted into the blood supply and removes pathogens from the blood and tissues.
Antibody effector functions
- IgG binds pathogens
- The variable region of the IgG binds to the antigens leaving the Fc domains exposed.
- Fc domains cluster to generate a signal to the rest of the immune system
Effector functions: complement
- IgG binds pathogens.
- Fc domains recruit complement and this leads to lysis of pathogens
- One such signal recruits a cascade of protein interactions called complement to the surface of the pathogen.
Opsonisation: phagocytosis
- Fc binding to Fc receptors on macrophages leads to phagocytosis and killing in lysosomes.
- This can be helped by complement.
- This phagocytosis pathway is also called opsonisation. Phagocytes can also generate reactive oxygen species (ROS) to help killing of pathogens.
Immunoglobulin A
- IgA is made by B-cells in response to infections of mucosal surfaces
- Two IgA molecules are joined by a protein called the J (joining chain)
- It is important for defence against infection at mucosal surfaces.
- It is secreted by B-cells but it does not stay in the blood, it is secreted across epithelial surfaces.
What does IgA bind to?
- Secretion occurs because the tail of IgA binds to an IgA receptor and this receptor traffics across the epithelial cells that line mucosal surfaces (for example gut and lungs).
- The secreted IgA is able to bind pathogens that have not yet entered the body.
What does immunoglobulin A defend?
- IgA defends mucosal surfaces
- 5 grams is secreted into the gut each day
Immunoglobulin E
- Immunoglobulin E (IgE) looks like IgG but the FC domain is different.
- This allows it to bind to IgE receptors that are found on mast cells and eosinophils.
- These cell types are full of granules that contain inflammatory mediators.
What is the function of IgE?
- IgE is mostly used to defend against parasites that try to live in mucosal surfaces or the skin.
- Binding of IgE to IgE receptors results in release of inflammatory mediators such as histamine.
IgE: Histamine
IgE causes histamine release from mast cells to open up sites of parasite infection to the rest of the immune system.
IgE: Allergy
- IgE is also the cause of allergies.
- If the body makes an IgE that recognises and allergen it will bind the allergen and trigger histamine release from mast cells.
- This can also contribute to asthma.
What do immunoglobulins defend?
-Immunoglobulins defend all sites of infection
T-cells
- T-cells do not secrete T-cell receptors.
- The receptor stays attached to the surface of the T-cell and it is the cell that determines immunological activity. -There are two main types of T-cell - Cytotoxic T-cells and helper T-cells.
What do cytotoxic T-cells do?
- Cytotoxic T-cells recognise infected cells and kill them so the pathogen has nowhere to live.
- This is particularly important for viruses because they cannot live outside cells.
- Cytotoxic T-cells contain granules filled with enzymes such as perforins that kill cells and release these enzymes into the space between the T-cell and the infected cell.
- Cytotoxic T-cell also kill tumour cells.
What do helper T-cells do?
-These are an essential part of the immune response because they help B-cell make the right antibody.
