Adaptive Immunity L8 Flashcards
what happens in the complement system
complement binding to the surface, “tagging” pathogen so it can be recognised more easily by other parts of the immune system
Three different pathwaysall lead to C3b on microbe
C3b tagging microbe – saying its infectious ,immune system gets information to know that it is infectious
Three different options after
what do B cells make
antibodies (immunoglobulins)
Cell surface (B cell receptor) or secreted
Protection against extracellular pathogens & toxins
what do T cells make
T cell receptors
Cytotoxic (killer T cells)
T helper cells
what is part of the innate immune system
PAMPS by means of PRRs
what is part of the adaptive immune system
Diverse molecules, including PAMPS, but
is adaptable to recognise new molecules
Has very specific recognition:
by specific antibodies and T cell receptors
what is PAMP
pathogen associated molecular pattern
what is PRR
pattern recognition receptor
what do PRRs do
maximally recognise hundreds of different PAMPS
the adaptive immune system is almost infinitely variable in its capabilities for specific recognition
what is an antigen
from antibody generator
what do antibodies bind to
Many antibodies may bind the same antigen, each a separate site termed an antigenic determinant or epitope
An antigen can also show repeated epitopes
Antigens can be diverse molecular structures
how are T and B cells similar
both have variable region where the antibody can vary massively
Both have constant region
Both embedded in the membrane – transmembrane region
how are antigens recognised by different antibodies
Antibodies recognise specific structures (epitopes) on the antigen in its original (native) shape
recognise different sections
what happens during antibody recognising antigen
epitopes recognised by Tcell receptors often buried
antigen must first be broken into peptide fragments
epitope peptide binds to self molecule, an MHC molecule
Tcell receptor binds to complex of MHC and epitope peptide
what are the two main types of MHC
class 1 and class 2
where are B and T cells from
lymphoid progenitor cells
where do B cells develop
bone marrow
where do T cells develop
thymus
what is somatic recombination, what does it cause
During development, rearrangement of the gene segments encoding the relevant genes occurs
gives each new cell a unique receptor combination
what does clonal selection cause
a specific response to an infection is based on a second mechanism
how doe individual B and T cells differ
Each individual B cell or T cell has a single receptor specificity
where can antibodies bind
can be bound to the surface of the B cell (B cell receptor) or they can be soluble
what is the variable region involved in
antigen binding
what is the constant region involved in
far less variable, involved in interaction with effector molecules and cells (see back to complement)
what is Fab
fragment antigen binding
what is Fc
fragment crystallisable
what are the five different antibody classes
IgG IgM IgD IgA IgE
how do antibodies differ
- Heavy chain length
- Hinge region
- Number of carbohydrates
- Disulphide bond position
what affects which class the antibodies are in
C region
which antibody is the most abundant in serum
IgG
what can IgM form
pentamers can bend and staple down to a surface and help activate the complement surface
what can IgA form
dimers
An example of how B cells stimulation to release antibodies
resting B cell encounter with antigen
stimulated B cell gives rise to antibody-secreting plasma cells
what are T cell receptors similar to
Similar to antibody Fab section
what are T cells made of
two chains
- α chain
- β chain
Variable and constant regions
where do antigens bind in T cell receptors
variable region, allows for specificity
where are antigens presented in T cells
Antigens have to be presented as peptides in MHC receptors
what is MHC
Major Histocompatability Complex
which cells have MHC 1 on their surface
All nucleated cells express MHC I on their surface so T cells can recognise it
which cells have MHC 2 on their surface
Only antigen presenting cells have MHC class II help to activate that part of the immune system
what happens in MHC antigen presentation
Virus taken into cell
Virus proteins synthesised in cytosol
Peptides then presented by MHC 1 on cell surface
Can happen on any nucleated cell
Cytotoxic T cell kills infected cells
Enzymes released by cytotoxic T cell break down genomic DNA of cell and virus cleave target proteins
how does cytotoxic T cell kill infected cell
cytotoxic T cell recognises complex of viral peptide with MHC 1
CD8 on bind to MHC 1
All T c to bind and kill cell
Don’t want this all the time so have different types of T cells
T helper functions
Th1 cell recognises complex of bacterial peptide with MHC 2 and activates macrophages
T follicular helper cell recognises complex of antigenic peptide with MHC 2 and activates B cell
