17/1 Adaptive immunology Flashcards
Adaptive immunology involves:
lymphocytes ( T & B Cells), highly specific antigen recognition, cytokines & collaboration with other cells
All immune responses can be divided into:
cell mediated and humoral immunity
cell mediated immunity
all responses in which antibodies play little/no part; involves T cells, macrophages, neutrophils, NKs
Humoral immunity
antibody mediated ( B cells)
define antigen
any substance that binds to specific receptors on lymphocytes i.e B cell/ T cell receptors
antigen can be many forms. List some
- may be protein, lipid, carbohydrate or any combination
- may be foreign or altered self molecule
- may be soluble or particulate, simple or complex with many diff. antigenic determinants
define antigenic determinant/ Epitope
part of antigen that binds to these receptors
any molecules or group of molecules that induce an immune response
immunogen
small molecule that can act as an epitope but not elicit an immune response
hapten
non microbe derived antigens might include?
pollen, food & dust or ‘self’ antigens from dead/ senescent cells or altered self molecules
non microbe derived antigens might include?
pollen, food & dust or ‘self’ antigens from dead/ senescent cells or altered self molecules
antigens can enter the body by various methods. List some
Breaks in skin & mucous membranes
Direct injection e.g. bite/needle
Organ transplants & skin grafts
Microfold cells in the mucosal surfaces
structure of antibody
Monomer: flexible Y-shaped molecule with 4 protein chain
Has variable region, constant regions, Fc region
what is the 4 protein chain in antibody structure?
2 identical light chains
2 identical heavy chains
Variable region in antibody structure
2 sections at the end of the Y arms
- contain antigen binding sites
- identical on the same antibody, but vary from one antibody to another- contains some hypervariable regions
constant region in antibody structure
stem of monomer on lower part of Y’s arm
Fc region on antibody structure
stem of monomer only
why is the Fc region important?
because they can bind to complement or cells
5 different classes of antibodies
IgG, IgM, IgA, IgE, IgD
why is each B cell different?
to make unique receptors
the class of antibody involved in immune response depends on:
type of foreign antigen, the portal of entry & the antibody function needed
what class of antibody can join together to form a secretary dimer?
IgA
what class of antibody has the lowest affinity for AB (antigen-binding)
IgM
structure of IgM
pentemeric, largest, lowest affinity for AB, 10 binding sites
structure of IgE
monomeric, highly glycosylated.
Most associated with allergy
the two heavy chains are linked by and each heavy chain linked to light chain by? antibody structure
disulfide bonds
function for IgA
Aggulation and neutralisation
where is IgA located?
muscous membrane secretions
Location of IgE
Serum, mast cell surfaces
location of IgG
Serum, intracellular fluid
location of IgM
Serum
function of IgE
Trigger release of histamines from basophils and mast cells
function of IgG
Complement activation, aggulation, opsonisation and neutralisation, crosses placenta to protect placent
Function of IgM
Complement activation, aggulation and neutralisation
antibodies bind to antigens based on?
the ‘complementarity’ of the epitope on the antigen & the antigen- binding (AB) site of the antibody
Approx. 10^13 different specificities can be generated of AB-AT interaction but actually more due to?
somatic hypermutation seen during immune response
the strength of AB-AT interaction is referred to as?
the affinity of the antibody
Which affinity (high/low) is more protective (AT-AT)?
High because it will bind antigens at lower concentrations
Antibody-antigen interactions are non-covalent. list some interactions
H-bonds, ionic bonds, hydrophobic interactions, van der Waals interactions
AB-AT interactions are reversible or irreversible
reversible
1 epitope of antigent binds to what part of AB structure?
variable region of antibody hypervariable regions
B cell stimulation requires what else?
cytokines from T helper cells
Co- stimulatory molecules ( CD19 + others)
1000-10,000x proliferation & differentiation of B cells into plasma cells packed with RER & highly metabolically active … happens once?
Once AB/B cell receptor has bound AT & signalled through the Ig alpha & beta chain (CD79a)
All immunogens are antigens but?
not all antigens are immunogens (not all antigens will produce an immune response)
On first exposure, there is a delay before specific AB seen in serum why? what type of immunity is this?
because it takes a while for cells to differentiate
- In humoral immunity kinetics
what is produced by T cells to stimulate plasma cell maturation?
cytokines
role of cytokines produced by T cells. Take how long?
to stimulate plasma cell maturation
- approx. 1 week
in humoral immunity what class of AB is poduced? then switches to ?
IgM, then switches to IgG , IgA or IgE
