Adaptive Immunity 1 Flashcards
What is the innate immune response?
- The first line of defence, fast but non-specific
- Humoral and Cell Mediated
What is the adaptive immune response?
Humoral and Cell-Mediated
It uses B and T lymphocytes respectively
What are the molecules used in the innate immune response?
PRR’s, that bind to PAMPS and DAMPS (these are generic molecules found on many different types of pathogen or released in response to stress or damage
What receptors are used in the adaptive immune response?
- Randomly generated B and T cell Receptors
- These are highly specific to individual antigen molecules, rather than generic molecules found on many pathogens
What is the definition of Humoral immunity?
Combatting pathogens using antibodies
What type of lymphocytes produce antibodies?
B lymphocytes
What is cell-mediated immunity?
This primarily involves T-lymphocytes
these can eradicate pathogens, clear infected self-cells or aid other cells in inducing immunity
What is the adaptive immune response based on?
The Clonal-Selection of antigen-Specific Cells
What proteins do helper cells and Cytotoxic cells interact with?
- Helper cells interact with CD4 T-cell receptors
- Cytotoxic cells interact with CD8 T-cell receptors
What is an antigen?
a processed peptide derived from a foreign or altered self-protein and presented by an MHC class I or II molecule
What is the structure of secreted immunoglobins/ antibodies?
- Two heavy chains
- Two light chains
- Held together by covalent bonds
How do B cells use genes to create antibodies?
They use parts of genes to create different possibel antibody combinations
What are the four mechanisms that generate antibody diversity in naive B cells?
- Multiple Gene segments
- Insertion of nucleotides between joints
- Exonuclease trimming
- Combinatorial diversity
Where does t cell progenitor development occur?
It occurs in the bone marrow
Where do T cells migrate to for further development?
the thymus
Where does b cell development occur?
The bone marrow and it is then completed in the periphery
Why do BCR receptors struggle to signal?
They have very little cytoplasmic domain
What chains do BCR complex with on the plasma membrane?
2 Iga and 2 Igb chains
How do Iga and Igb signal?
they have signalling motifs in their cytoplasmic chains
What is the activator motif for iga and igb?
ITAM (immunoreceptor tyrosine-based activation motif)
How do the signalling cascades from iga and igb become triggered?
phosphorylation of the ITAMS which goes on to trigger a signalling cascade
Are T-Cell Receptors antibodies?
No
but they belong to the Ig superfamily of proteins
What chains do the T Cell antibodies contain?
They contain both beta and alpha chains
What CD complex binds to the TCR receptor to aid in signal transduction?
CD3
What is allelic exclusion?
Makes sure that each B cell synthesises only one light and one heavy chain
What is the double negative stage of T cell development?
Thymocytes do not show the receptors for either CD4 or CD8 therefore they cannot become either T helper or T Cytotoxic
What is the double positive stage of thymocyte selection?
after beta selection, the thymocytes express both CD4 and CD8 receptors
What cells are removed in the final T-Lymphocyte screening?
autoreactive t cells
Where are non-reactive lineage T cells released?
They are released into the peripheral bloodstream
What is the first basic step of B Cell Production?
Recombining the heavy chains
If this is succesful it initiates recombination of the L chain
What is Central tolerance in terms of B cells?
Occurs in the bone marrow
The clonal deletion of strongly autroreactive cells via apoptosis
What is receptor editing in terms of B cells?
reactivation of the recombination machinery
does not occur in T cells!
Where do the final stages of B cell maturation occur?
In the spleen
What is the difference between positive and negative selection and why does it only occur in T cells?
Positive selection is when T cells in the thymus are kept because they have MHC molecules
Negative selection is when inactive T cells in the medulla of the thymus are removed due to them being inactive
In B cells only negative selection occurs as they do not have MHC molecules
What is the function of CD19?
Acts as a co-receptor on B cells, helps to amplify the signalling
What is the function of Tyrosine kinase?
Phosphorylation of tyrosine kinase triggers different signalling cascades (different signalling pathways) in the B cell
What is the structure of TCR’s?
they are heterodimers and possess both an alpha and a beta chain
What does CD3 complex with to assist in antigen recognition?
TCR’s
What co-receptors also bind to the MHC molecule to aid signal transduction?
CD4 and CD8
What do the initial activation signals induce in T helper cells?
- Up-regulation of pro-survival genes
- Transcription of IL-2 and IL-2R genes
What do cytokines do in T cell activation?
Depending on which cytokines are present, can send the T cells down different activation pathways
What subsets can T helper cells be divided into?
- Th1, Th2
- Th17
- Treg
- TFH
