Adaptive immunity- extracellular Flashcards
which cell act was a bridge between the immune and adaptive immune system
antigen presenting cells
if naive T cells and pathogen meet
no response
only way T cells can be activated is by
antigen presenting elsl
APCS
phagocytose and process the microbe and present it to the Naïve T cell so they can recognise pathogen/tumour cell
naive T cell
T cell that have no previously encountered the antigen
effector T cell
T cells that have previously encountered the antigen are capable of performing the effector functions during an immune response
Antigen presenting cells role
- Sense the pathogen
- Capture pathogen
- Process pathogen
- Present the pathogen to T cells
name 4 APC
dendritic cells
langerhans
macrophages
B cells
dendritic cells and langerhans (dendritic cell specialised for the skin) present the pathogen to ……………. and have what function
present to naive T cells
Function: T cell response against most pathogens
macrophages and B cells present the pathogen to …………….
present to effector T cells
function of macrophages
phagocytic activities
function ofB cells
antibody response (humeral)
APC are found in strategic locations
- Mucosal membrane (gut, lung)
o Mucosal associated lymphoid tissue (MALT) - Skin (Langerhans cells)
o Skin associated lymphoid tissue) - Blood (plasmacytoid cells)
- Lymph nodes (follicular dendritic cells)
- Spleen
pathogen capture method of APC
- Phagocytosis (whole microbe)
- Micropinocytosis (soluble particles)
2 types of microbes
- Extracellular
o Fungal
o protozoa
o Most bacteria - Intracellular
o Virus
o TB
o Cancer
PRRS recongise
intracellular and extracellular pathogens PAMPs
TLR recognise extracellular pathogens
TLR1,2,6,4,5,11
- TLR4- Neisseria meningitidis- sepsis
TLR recognise intracellular pathogens
TLR3,7,8,9
how do APC activate the adaptive immune system
- Macrophages and APC recognise pathogen
- APC use lymphatics to get to lymphoid tissue
- APC presents to T cells
Major histocompatibility complexes (MHC) molecules are a type of
human leukocyte antigen
HLA
human body version of MHC
- how pathogens are presented to naive T cells
MHC I
- Expressed on all nucleated cells
- CD8 cytotoxic T cells
- Kill intracellular pathogens
• Virus’
• TB
• Cancers
MHC II
- Expressed on APCs, dendritic cells, macrophages and B cells
- CD4 T helper cells
• Fungal
• Bacteria
• Parasitic
key features of MHC molecules
- Co-dominant expression
o Both MHC class I and II parental molecules are co-expressed in each individuals (6 of each class) - Polymorphic genes (diff alleles)
o Different individuals present and respond to different microbes
Antigen presenting cells present intracellular microbes via MHC class I molecules
HLA-A, B and C
Extracellular microbes presented by MHC class II molecules
HLA-DP, HLA- DQ, HLA-DR
processing of intracellular microbes (MHC I)
- Viral proteins present in the cytosol
- Marked for destruction by proteasome
- Proteasomes-generated viral peptides transported to ER by TAP proteins
- Formation of viral peptide- MHC class I complex if right match (coded in genome)
- APCS and non-APC present peptides from intracellular pathogens to CD8+ T cells
- T cells only react when sensing a foreign peptide
- Also present self peptides in this way
Processing of extracellular microbes Exogenous pathway (MHC II)
- Microbes captured by phagocytosis or micropinocytosis
- Degradation in small peptides in the endosome
- Peptide rich vesicles fuse with vesicles containing MHC class II molecules
- Formation of peptide MHC class II complex if right match
- APCs present peptides extracellular pathogens to CD4+ T cells
MHC I found on
all cell types
MHC II found on
APCs- dendritic, B cells and macrophages
peptide bonding cleft on the MHC molecules
highly variable region with highly polymorphic residues (coded for in the genome)
MHC I occurs as an α chain composed of three domains
—α1, α2, and α3.
MHC class II is formed of
two chains, α and β, each having two domains—α1 and α2 and β1 and β2—each chain having a transmembrane domain, α2 and β2, respectively, anchoring the MHC class II molecule to the cell membrane.
no individual has the same set of
mHC moleculen
Individuals have different susceptibilities rot infection
o Strong vs weak immune response against infectious microbes
Pregnant
Immunosuppressed
Children
HLA molecule mismatch between donor and recipient (allograft) is
a major cause for organ transplant rejection
GRAFT VERSUS HOST REACTION (GVH)
HLA association with autoimmune disease
- Ankylosingspondylitis
o HLA-B27 -> 90% of patients - Insulin-Dependent Diabetes Mellitus
o HLADQ2 -> 50-75% of patients
