Week 5- Lymphocytes Flashcards
What cells are involved in the adaptive immune response?
Haemopoeitic stem cells, lymphoid progenitor cells, B/T cells
What does the adaptive immune response do?
Creates memory for protection against future infection and specificity to clear the infection. Is localized to the infected cells/organism responsible, helps improve efficacy of the innate immune response
How does immunological memory arise?
It is a consequence of colonial selection, antigen specific B/T cells are the basis and can confer life long immunity
What are the 2 different types of adaptive memory?
Humoral: B cells that produce antigens
Cell mediated: T cells produce cytokines and kill cells
What is an epitope?
The variable region of an antigen where the antibody binds
What type of epitope do T cells recognize?
Linear epitopes: strings of amino acids
What type of epitope do antibodies recognize?
Structural epitopes: 3 dimensional shapes
How is variety achieved with B/T cells?
By gene recombination and the V and J regions being able to bind in different combinations
What are the 2 main types of T cells?
CD8 & CD4
How are CD4 T cells activated and what is their function?
They are activated when they meet an APC, they divide to form clones and can assist in repair (by producing cytokines that activate T cells, helping the immune response be appropriate), immune memory and causing allergic reactions
How are CD8 T cells activated and what is their function?
They are activated when they meet an APC and are cytotoxic (they kill infected cells and pathogens by apoptosis) and form memory cells
Describe the T cell receptor
The variable region is made by gene reassortment, they recognize antigen fragments that are presented to them by other cells
What is the major histocompatibility complex?
It is a complex that defines wether cells are self or non self
What gene encodes for the major histocompatibility complex?
HLA gene
What types of major histocompatibility complex exist and which cells display what types?
All cells present MHC I but only APCs present MHC II
What is the function of MHC I?
To present the proteins being synthesized in the cell of the cell surface to allow immune cells to monitor wether the cell is synthesizing self or non self proteins eg is making non self proteins it could be infected by a virus
Where is MHC I found and processed?
Intracellularly, processed in cytosol
What immune cell does MHC I communicate with?
CD8 T cells
What is the function of MHC II?
It is the complex onto which dendritic cells that have engulfed foreign pathogens present foreign antigens to the immune system
Where is MHC II found and processed?
Extracellular, processed in endosol
Which immune cell does MHC II communicate with?
CD4 T cells
What are the 2 main molecules T cells store?
Perforin (polymerizes to form pores) and granzymes
What are the 5 classes of antibodies and what heavy chains do they have?
IgA- alpha heavy chain IgG- gamma heavy chain IgD- delta heavy chain IgE- epsilon heavy chain IgM- mu heavy chain
What are the 3 main roles of antibodies?
- Neutralisation- prevents adherence of the pathogen to other cells
- Opsonisation- enhances phagocytosis
- Complement activation- helps with opsonization and can cause lysis of some bacteria
How are B cells specific?
They only produce one specific antibody, their binding site is made before they encounter any antigens
Describe the 2 paths by which B cells are activated. Can they be activated just via antigens?
A naive antigen specific B cell cannot be solely activated by encountering antigens, it requires a signal from either T cells (more common) or from microbial constituents (rare)
From T cells: thymus dependent path, all Ig class antibodies can be involved, once a foreign antigen is encountered it is internalized, it peptides are degraded and they associate w self molecules. It is them displayed on the cell surface and recognized by CD4 T cells which can activate B cells
From microbial constituents: thymus independent antigens, 2nd signal can be via microbial constituents or accessory cells. Only IgM antibodies are involved and no memory is produced
What antibody class/classes are involved with T cell activation of B cells? Is there memory? Is it thymus dependent or independent?
All Ig classes are involved
Memory is formed
Thymus dependent
What antibody class/classes are involved with microbial constituent activation of T cells? Is it thymus dependent or independent? Is memory involved?
Only IgM class
Thymus independent
No memory
