Adaptive Immunity Flashcards
Describe features of APCs
Strategically located in skin, mucous membranes, lymphoid organs and blood plasma.
Pathogen capture by phagocytosis or macropinocytosis.
Diversity in PRRs- extra cellular for bacteria and intra cellular for viruses
Describe the role of MHC molecules
Present antigens to T cells naive or effector
How are microbial antigens processed and presented to T cells?
Exogneous and endogenous pathways of antigenic peptide presentation by MHC molecule. TCR of naive T cell will bind the antigen and the T cell wll either be CD4 positive or CD8 positive dependent on if the microbe in intra or extracellular and thus the MHC class type. There are other receptors involved in the two cell interaction and cytokines play a part as well.
What do T helper cells do in determining appropriate immune responses for intra and extra cellular pathogens?
If a CD8+ T cell is activated by an APC the cytotoxic immune system is activated. The cytotoxic T cells will recognise the MHC class I on all virally infected cells and cause death by perforin granzymes. CD4+ TH1 will also stimulate B cell and macrophages.
If CD4+ T cells are activated the humoral response is activated. CD4+TH17 will stimulate neutrophils in the presence of IL-17. CD4+TH2 in the presence of IL-4 will stimulate B cells and mast cells. CD4+TH2 in the presence of IL-5 will stimulate eosinophils.
Name the MHC class 2 molecules
HLA-DR
HLA-DQ
HLA-DP
Outline the genetics of MHC molecules.
Polymorhic
Co-dominant expression
What is the role of MHC class 1 molecules and where are thy found?
They are found on all cells and present antigens from intracellular pathogens.
What is the role of MHC class 2 molecules and where are they found?
MHC class 2 are only found on APCs and so deal with extracellular pathogens.
Outline MHC structure
Peptide binding cleft - variable highly polymorphic region
Broad specificity- one MHC can present lost of antigens
CD8+ T cells cells respond to what type of pathogen and thus which MHC molecules present to it?
CD8+ cells deal with intracellular pathogens and are thus activated by MHC class I. Remember APC will present on both MHC class I and MHC class II when it comes to intracellular pathogens.
CD4+ recognise which class of MHC?
Class II
Describe the two APC pathways.
Endogenous pathway- MHC Class I detects antigenic peptide in the ER and mobilises to the plasma membrane to present it.
Exogenous pathway-MHC Class II are released by ER and fuse vesicles with the endosomes containing antigen peptides and the vesicle will move to present on the plasma membrane.
Do MHC molecules present only non-self peptides?
No they will present self peptides as well
How many peptides from a microbe are presented on MHC molecules?
All peptides are presented on different MHC molecules.
How do MHC molecules effect susceptibility to infections?
The type of MHC an individual has will effect how susceptible they are to different infections.
Elite controllers of HIV will maintain low viral load and high CD4 count because they have MHC molecules that present vital peptides to the HIV virus. Other suffered may present non-vital peptides but these can mutate and thus doesn’t give good control of the virus and these patients are termed progressors.
