Adaptive immune system Flashcards
What is immunological memory
Exposure of immunologically primed animal to same antigen leads to activation of B memory cells which were established during primary immune response
Enhanced immune response is outcome
Role of T cell vs B cell in adaptive immunity
T cell = cell mediated immunity (direct killing of abnormal cells)
B cell = humoral immunity (production of antibodies)
What is the role of helper T cells (CD4+)
Coordinate immune response by activating other immune cells (e.g. B cells & cytotoxic T cells)
Do this by producing cytokines which are signalling proteins that help modulate immune response
What is the role of cytotoxic T cells (CD8+)
MCH1
Directly kill cells that are infected with intracellular pathogens & cancer cells
Recognise & bind to specific antigens presented on surface of infected cells
Release cytotoxic molecules that induce cell death
What is the role of regulatory T cells
Suppress excessive immune responses & prevent autoimmunity
Modulate activity of other immune cells (e.g. T & B cells)
B cell role in antigen recognition & activation
B cells have unique receptors on surface (B cell receptors) that recognise specific antigens
Once B cell encounters specific antigen, it becomes activated & undergoes clonal expansion
Results in production of identical B cells that all recognise same pathogen
B cell role in plasma cells & antibody production
Activated B cells differentiate into plasma cells (primary producers of antibodies)
Antibodies secreted into blood stream where they bind to target antigens & neutralise them
B cell role in memory B cells
Some activated B cells develop into memory B cells
Persist long term & can rapidly produce antibodies in response to subsequent encounter with same antigen
B cell receptor structure
Membrane bound immunoglobulins (Igs) that are expressed on surface of B cells
Consists of 2 identical heavy chains & 2 identical light chains
Each heavy & light chain has variable & constant region
Variable regions of heavy & light chains come together to form antigen binding site
B cell receptor function
Recognise & bind to specific antigens
When it binds to antigen it triggers signaling cascade within B cell leading to activation, proliferation & differentiation of B cell
Activated B cells can then differentiate into plasma cells which secrete antibodies or memory B cells
T cell receptor structure
Composed of 2 different polypeptide chains with variable & constant region
Variable regions join together to form antigen-binding site
T cell receptors are always membrane bound & never secreted like antibodies
T cell receptor function
Recognise & bind to peptide antigens presented on surface of other cells by major histocompatibility complex (MHC) molecules
2 types of MHC molecules – MHC class 1 presents viral antigens & is recognised by cytotoxic T cells (CD8+) - MHC class 2 presents bacterial antigens & is recognised by helper T cells (CD4+)
Once TCR binds to specific antigen MHC complex, it activated T cell leading cytokine production, cytotoxic activity or B cell activation
