antigen processing

• professional antigen presenting cells

  B cells, dendritic cells, macrophages
• naive T cell activation

  clonal expansion and differentiation into effector T cells (CD4T and CD8T)
• effector t cell response(macrophage)

  macrophage activation (cell mediated immunity), CD4T cells secrete IFN-y to activate macrophages
• effector t cell response (B cell)

  B cell activation by CD4 cells, helping them generate high affinity antibodies, memory, IgA, IgG, and IgE
• high endothelial venules

  specialised blood vessels in secondary lymphoid organs, important for lymphocyte and dendritic cell migration into secondary lymphoid organs
• afferent lymph vessels

  comes into
• efferent lymph vessels

  comes out
• CD4T

  differentiate into helper T cells, and interact with MHC class 2
• CD8T

  differentiate into cytotoxic T lymphocytes, that kill infected and tumour cells, interact with MHC 1
• B lymphocytes


  bind unprocessed antigen, and differentiate into plasma cells
• DC4T cells require a precessed antigen, which is usually an exogenous antigen
• CD8T cells require a processed antigen, which is usually endogenous
• intracellular antigen processing

  endogenous, synthesised within the cell, eg. self proteins, viral proteins, intracellular pathogens, eliminated by cytotoxic t cells
• extracellular antigen processing

  exogenous, enter by endocytic pathway, eliminated by antibody
• cross presentation

  APC take up, process, and present extracellular antigens with MHC class 1 to CD8 T cells, this is important for immunity against tumours and viruses that dont infect APC
• endogenous antigen processing

  MHC class 1 and peptide presentation to CD8 t cells
• exogenous antigen processing

  MHC class 2 and peptide presentation to CD4 T cells
• there is no t cell activation without co-stimulation
• signals of co stimulation

  TCR binding to MHC and peptide, and then co stimulation
• one costimulation signal alone leads to anergy or tolerance
• Th1

  IFN-y, IL-12
• Th2

  IL-4
• Tfh

  IL-6 produces IL-21
• CD8 cytotoxic t cells

  kills virus infected cells, and some intracellular bacteria
• CD4 Th1

  activate infected macrophages and provide help to b cells for antibody production, targets extracellular bacteria
• cd4 Th2

  provide help to b cells for antibody production, especially switching to IgE, targets helminths and parasites
• CD4 Th17

  enhance neutrophil response, promote barrier integrity, targets extracellular bacteria and fungi
• Tfh cells

  b cell help, isotope switching, antibody production, targets all pathogens
• CD4 regulatory t cells

  suppress t cell responses
• ILC1

  immunity to intracellular bacteria and protozoa, chronic inflammation
• ILC2

  immunity to helminths, asthma, metabolic homeostasis
• ILC3

  lymphoid tissue development, intestinal homeostasis, immunity to extracellular bacteria, chronic inflammation
• CD19

  adaptor molecule for activation
• CD21

  complement coated pathogen activates this protein
• CD81

  enhances signalling
• thymus dependant antibody production signals

  BCR complex and BCR co receptor complex + antigen, and Tfh
• thymus independent B cell responses

  multiple BCR cross linking by polyvalant antigen, and TLR signalling
• t independent B cell responses produce:

  low affinity antibodies, that are important for protection against encapsulated organisms
• TI-1 antigens

  cause proliferation and activation of B cells
• T dependant anti body production enables:

  antibody secretion, isotope switching, affinity maturation, and memory B cell