Lymphocytes Flashcards
What is adaptive immunity?
memory against recurring infection
What is an epitope?
regions of antigen where receptor will bind to
How do T cells recognise antigens?
T cells recognise primary sequence structure of MHCs (proteins)
How do B cells recognise antigens?
B cells recognise 3D structure - how protein folds in place
How do lymphocytes deal with antigen diversity?
All combinations of receptors are made.
Enforce ma
A BCR on a B cell is the same as the antibody it produces. Why is an antibody unique?
BCR gives unique mRNA. Therefore unique antibody
Light gene and heavy gene combine. The genes loop. V and J.
What is IMMUNOGLOBULIN GENE REARRANGMENT
Each BCR (antigen specific receptor) encoded by separate multigene families. During B cell maturation, gene segments rearranged and brought together
What are 2 types of T cells?
- CD8+ (cytotoxic, kill pathogens)
- CD4+ (normal, clones)
How do TCR (T cell receptors) work?
- recognises linear antigen fragments
- receptor cell clustering
- Once it sees antigen, intracellular cell signalling.
What do MHC do?
Define self and non self cells
What is MHC coded by?
HLA genes
MHC is polygenic. What does this mean?
It encodes several different versions of the same things
MHC expression is co dominant. What does this mean?
maternal and paternal genes both expressed
How many classes of MHC are there?
MHC class 1 (INTRACELLULAR MATERIAL) MHC class 2 (EXTRACELLUALR)
How does class 1 MHC work?
- class 1 presented on all uncleared cells.
- They present proteins made in cell on cell surface, so body recognises as self.
- Talk to CD8 Viral proteins on MHC show foreign.
how does class 2 MHC work?
- on antigen presented cells.
- Dendritic look for infectious material.
- Present on MHC.
- Talk to CD4.
How do CD8 work?
- kill cells by apoptosis
- Fragmentation of nuclear DNA
- CTL store performing, granzymes, granulysin in cytotoxic granules
- Perforin molecules polymerise, form pores
How does cd4 work?
Produces cytokines
Why do B cells need help from T cells when making antibodies?
They only recognise soluble antigens, and have no MHC
What is the variable region in antibodies for?
Specifity
What is the constant region in antibodies for?
Functionality
Name 3 roles of antibodies:
- neutralisation (binding to virus)
- Opsonisation (promotes phagocytosis)
- Complement activation (enzyme cascade reactions leading to bacterial cell death)
What sends naive B cells an accessory signal? (Apart from antigens)
- from microbial constituents ( T independent, only form IgM.) These molecules cluster BCR together, starts signalling cascade. No memory
- T cell helper. All iG classes and memory.
Roughly, how is a B cell activated by a T cell?
- BCR recognises antigen
- B cell engulfs antigen
- Presents on MHC2
- T CD4 cell that recognised same antigen on DENDRITIC recognises B cell
- B cell activated
