Adaptive Immunity Flashcards
What is innate immunity
The first line of defence of (non specific) defence whilst adaptive immunity is specific and acquired
What does the adaptive immune response consist of
Cell mediated responses and antibody (humoral) responses
Describe T cells
T cells drive cell mediated immunity, involves the activation of macrophages,natural killer cells (NK) and antigen specific helper and cytotoxic T lymphocytes
Describe B cells
Produce antibodies and drive humoral immunity
What is a key feature of the adaptive immune system
Immunological memory, whereby each pathogen is remembered by a signature T cell and/or B cells
What are the three main receptors in adaptive immunity
- T cell receptor
- B cell receptor ( immunoglobulins)
- major histocompatibility complex (MHC proteins)
Where do T cells mature
The Thymus
What peptides do T cells recognise
Recognise peptides presented by APCs through the T cell receptor
What is T cell repertoire
Diversity is T cell receptor
What is thymus education
Checkpoints in place however ensure T cells only respond to foreign pathogens
What are T helped cells
CD4+ function to help supports other immune cells to fight threats
What are cytotoxic T cells
CD8+ destroy our own cells which have become infected
What are regulatory T cells
Regulate or suppress other cells in the immune system
What do all T cells start as
Naive cells and they all have specific receptors
What is the CD8 receptor
A co receptor that binds to MHC 1
What is a CD4 receptor
A co receptor that binds to MHC II
What is CD3 receptor
A co receptor involved in activation of both CD4+ and CD8+ T cells
What chains do the majority of T cells express
Alpha and beta chains
What chains do the minority of T cells express
Gamma and delta cells
What are the three gene segments that encode the variable region of the T cells
- V (variable) (both alpha and beta chains)
- D (diversity) (beta chain only)
- J (joining) (both alpha and beta chains)
What are the regions called in the T cells that can change
- constant region
- variable region
What are the genes re arranged by in T cells
Somatic recombination
What is the process of multiple genes encoding for a T cell receptor called
VDJ recombination
What enzyme is used for recombination of genes in T cell receptors
RAG (recombinase) enzymes
Where are T cells educated
In the thymus
What are the two types of selection
T cells interact with thymic cortical epithelial cells in thymus
- positive selection - no recognition = apoptosis
- negative selection - recognition of self antigen = apoptosis
What is T cell emigration
Positively and negatively selected CD4/CD8+ T cells with rearranged T cell receptors leave the thymus and circulate in blood/lymphatics
Some reside in lymph nodes
They are still classes as naive
What cells prime naive T cells
Mature dendritic cells
What three signals are required for the priming of T cells
Signal 1 = activation of T cells
Signal 2 = survival and clonal expansion of T cells - signal 1 but no signal 2 is known as anergy
Signal 3 = differentiation into subsets of effector T cells (specifically CD4+ helper cells)
What is the role of CD4+ T cell subsets (TH1 cells)
Main role is macrophage function
Source of interferon - delta
What is the main role of CD4+ T cell subsets - Treg cells
Regulatory T cells that function in immune suppression
Release inhibitory cytokines
Inhibit T cell activation and dendritic cell activation
What can happen if there are not enough Treg cells
Extensive inflammation
What is the function of CD8+ T cells
Induce host cells to undergo apoptosis
What do cytotoxic T cells release
Granzyme/perforin
