Linking Innate and Adaptive Immunity Flashcards
Describe the major immune cell communication methods
- Soluble molecules (cytokines and chemokine) binding to receptors on a cell membrane
- PAMP, cytokine and chemokine receptors allow for up or down regulation of gene transcription
- Chemokine receptors can also activate molecules that direct cell movement (they are molecules that lead to some kind of movement) - Cell surface-bound receptors binding to cell surface-bound ligand (how T and B cells communicate)
- No ligand: only the cell with the receptor gets activated/altered
- Ligand: both can get the signal (and be activated/altered in some way) - Antigen (pathogen parts) being presented to cell surface-bound receptors
- MHC presents antigen to T cell receptor. If it is the correct antigen for the receptor and T cell then a signal will be sent (lock and key, if it doesn’t fit it won’t work)
What is ‘antigen’?
Anything that has the potential to be recognised by the immune system
- Foreign antigen: anything from ‘outside’ (transplants, pathogens, some chemicals)
- Self-antigen: immune system usually tolerant of self-antigen
- T cells in the Thymus are presented with self antigen so they learn not to react with it.
Describe activated dendritic communication with T cells
Activated dendritic cells:
- Make cytokines that bind to receptors in T cell membranes
- Have cell surface bound receptors that bind to T cell surface-bound ligand (or vice versa)
- Present antigen to cell surface-bound receptors on T cells
This communication leads to activation of the T cell.
It is an example of innate and adaptive immune responses activating.
Describe the major histocompatibility complex (MCH)
MHC from/on the dendritic cell holds/presents antigen to T cell receptor.
If it fits ‘lock and key’ then the T cell will get activated
What are the two types of major histocompatibility complex (MHC)?
- MHC-I presents endogenous (intracellular) antigen. Expressed on all nucleated cells.
- MHC-II presents exogenous (extracellular) antigen. Expressed only on antigen presenting cells such as dendritic cells.
Describe cytokines and chemokines
- Cytokines are molecules such as interleukins and interferons (chemical messengers) that control growth and activity of immune cells
- Chemokines are molecules that stimulate cell migration
- Both are produced by innate and adaptive immune cells as cells that influence the immune system (eg. epithelial cells)
Describe how helper T cells activate B cells
Helper T cells that have been activated by a dendritic cell can then ‘help’ B cells by:
- Making cytokines that bind to receptors on B cell membranes
- Have cell surface-bound receptors that bind to a B cell surface-bound ligand (or vice versa)
This communications leads to activation of the B cell, and helps B cell to make antibodies.
Describe how linking innate and adaptive immunity works in terms of B cells and compliment
- Antibody binding to a pathogen can trigger the classical pathway of compliment activation
- AND… compliment fragments that are bound to antigen can also help activate B cells to make antibodies.
- These are both examples o how innate and adaptive immunity interact with each other.
Summarise and put together all of the steps involved with an immune response when you step on a nail
- Stand on nail, breaking the physical barrier (skin)
- Pathogens enter the body
- Chemical mediators lead to vasodilation and entry of phagocytic cells to the tissue to ‘eat and destroy’
- The compliment pathway is triggered
- Dendritic cells in the skin become activated through recognition of pathogen associated molecular patterns
- Dendritic cells move to local lymph node
- Activated dendritic cells activate T cells via MHC
- Antigen + T cells and compliment activate B cells
- B cells produce antibody
- Compliment, phagocytosis and antibodies help clear pathogen
