CMB1003/L24 Cell-mediated Specific Immunity I Flashcards
What is the structure that processes antigen presented molecules?
MHC - major histocompatability complex
What is the function of T cells? (2)
Kill virus-infected cells
Modulate activities of other cells e.g., B cells
Describe the structure of the T cell receptor (TCR). (4)
Heterodimer
a and B chains linked by S-S bridge
Each chain has V and C region
V regions concerned with Ag recognition
Both chains have hydrophobic transmembrane region and short intracellualar tail
What does the BCR (B cell antigen receptor) recognise?
Free antigen
What does the TCR (T cell antigen receptor) recognise?
Ag on other cell surfaces as complex of peptide + MHC molecule
Via peptide fragment (epitope) of Ag
Which cells is MHC class I expressed by?
Nearly all cell types
Not RBC
Which cells is MHC class II expressed by?
APCs
What do cytotoxic T cells recognise? (2)
p/MHC class I complexes on cells usually express CD8
Kills infected cell via apoptosis
Which kind of Ag does MHC class I allow recognition of?
Intracellular
Which kind of Ag does MHC class II allow recognition of?
Extracellular
Describe the internalisation and presentation of extracellular antigen by MHC class II. (4)
Antigen taken up from ECS into IC vesicles
Early endosomes of neutral pH, endosomal proteases inactive
Acidification of vesicles activates proteases to degrade antigen into peptide fragments
Vesicles containing peptides fuse with vesicles containing MHC class II molecules
Give 2 types of APCs.
Dendritic cells
Macrophages
What is the role of CD4+ helper T cells? (2)
Recognise antigens taken up by APCs and presented by MHC class II
Modulate activities of other cell types via cell-cell interactions and cytokines
How do T(H) cells leave the thymus?
As T(H)0 cells
How do T(H)0 cells become polarised?
Recognition of p/MHC II complexes on APCs
What is the role of T(H)1 cells? (2)
Activate macrophages
Help kill intracellular pathogens
What is the role of T(H)2 cells?
Help kill extracellular parasites
What is the role of T(H)17 cells?
Promotes response to kill extracellular bacteria and fungi
What is the role of T(FH) cells? (2)
Stimulates naive B cell differentiation
Produce class-switched antibodies
What is the role of T(reg) cells?
Suppress activation of the immune system
What is the type 1 CD4+ response? (2)
Phagocytosis of pathogens by macrophages
Evasion of intracellular killing
Which cytokine is required for B cell class switching?
IL-4 produced by T(H)2 cells
Describe the type 2 CD4+ response. (2)
Help recruit and promote response by eosinophils and mast cells
IL-4 produced to fight parasites
Which response are T(FH) cells involved in?
Type 1 and 2
What is the role of IFNy? (3)
Secreted by T(H)1 cells
Activates macrophages
Produces more T(H)1 cells
What is the role of IL-4? (3)
Induces class switching to IgE
Recruits mast cells, eosinophils, basophils
Produces more T(H)2 cells
What is the role of IL-21?
Secreted by T(FH) cells
Help B cells become antibody-secreting (plasma) cells
What is the role of IL-17? (3)
Secreted by T(H)17 cells
Involved inflammation and anti-microbial immunity at epithelial/mucosal barriers
Recruit neutrophils
What is the role of IL-10 and TGF-B? (2)
Secreted by T(regs)
Suppress activation of immune system
