3. Antibodies production is the sole function
of the B cells
Not toxic or destructive, bind the
pathogen tightly and target destructive
components of the immune system
Antibodies are useful in the defense
against extracellular pathogens
Antibodies are secreted in the secondary
lymphoid organs and in bone marrow and
find their way to the extracellular spaces
During the course of an infection
antibody effectiveness improves steadily
12. FEATURES OF ANTIBODY-ANTIGEN INTERACTION
Valency: numbers of antigen
epitopes an antibody binds
Affinity: the strength of
interaction between a specific
antigen and one binding site
of the antibody
Avidity: The overall strength
of binding at multiple sites in
an antibody
14. Sequence variability of H/L-
chain constant regions
VARIABILITY IN DIFFERENT REGIONS OF THE Ig
DETERMINES Ig SPECIFICITY OR CLASS
isotype
Sequence variability of H/L-
chain variable regions
Idiotype
16. ANTIGEN BINDING FRAGMENT (Fab)
CONTAINS HYPERVARIABLE REGIONS
DNA recombination of gene
segments encoding these
regions (variable heavy and
light polypeptide chains) gives
a huge number of variability
during B cell development in
the bone marrow.
Aka. Somatic recombination
18. Sequence variability of H/L-
chain constant regions
VARIABILITY IN DIFFERENT REGIONS OF THE Ig
DETERMINES Ig SPECIFICITY OR CLASS
Sequence variability of H/L-
chain constant regions
Isotype
19. • IgG - gamma (γ) heavy chains
• IgM - mu (μ) heavy chains
• IgA - alpha (α) heavy chains
• IgD - delta (δ) heavy chains
• IgE - epsilon (ε) heavy chains
HUMAN IMMUNOGLOBULIN CLASSES
ENCODED BY DIFFERENT STRUCTURAL GENE SEGMENTS (ISOTYPES)
• kappa (κ)
• lambda (λ)
Heavy chain types:
Light chain types:
!
22. Ig isotype Serum
concentration
Characteristics, functions
12-14 mg/ml
Major isotype of secondary
(memory) immune response
Complexed with antigen activates
effector functions (Fc-receptor
binding, complement activation
Trace
amounts
The first isotype in B-lymphocyte
membrane
Function in serum is not known
Trace
amounts
Major isotype in protection against
parasites
Mediator of allergic reactions (binds
to basophils and mast cells)
3-3,5 mg/ml
Major isotype of secretions (saliva,
tear, milk)
Protection of mucosal surfaces
1-2 mg/ml
Major isotype of primary immune
responses
Complexed with antigen activates
complement
Agglutinates microbes
The monomeric form is expressed in
B-lymphocyte membrane as antigen
binding receptor
MAIN CHARACTERISTICS OF ANTIBODY ISOTYPES
24. Ig. Concentration
napok
primer response
„A
” antig n
é
IgM
IgG
IgA
IgE
Szekunder ’lasyecondary respo
„A
” és
antigén
„B
”
5 10 15 20 25 30
IgM
secondary response against
antigen A
Primary response
against antigen A
Level of antibodies
napok
primary response
against antigen B
Antigen A
Days
Antigen A and B
ANTIBODY PRODUCTION DURING THE
PRIMARY AND THE SECONDARY IMMUNE RESPONSES
29. OPSONIZATION
Flagging a pathogen
Antigen binding portion (Fab)
binds the pathogen, the Fc
region binds phagocytic cells
Fc-receptors speeding up the
process of phagocytosis
31. (A) High-affinity FcRs on the surface of the cell bind monomeric
Ig before it binds to antigen. (mast cell)
(B) Low-affinity FcRs bind multiple Igs that have already bound to
a multivalent antigen. (macrophage, NK cell)
MAST CELL DEGRANULATION
FcεRI
+
IgEs
36. Antigen binding
Complement binding site
Placental transfer
Binding to Fc receptors
FcRn on the placenta
facilitate the transfer of
maternal IgG to the fetus’s
circulation
37. IgG
IgM
IgA
AFTER BIRTH
breast milk
IgA
0
100%
( adult)
3 3
year
2 5
4
6 adult
9 1
month
maternal IgG
BEFORE BIRTH
PRODUCTION OF IMMUNOGLOBULINS
IgG transport is so efficient that at birth babies have as high a level of IgG in
their plasma as their mothers
These transfers are a form of passive immunization. The babies protection by
IgG and IgA is against those pathogen that the mother has mounted
At the first year (esp.3-12m) maternal IgGs are catabolized and breast feeding
diminishes so babies become most susceptible/vulnerable to infections
38. Pathological consequences of placental
transport of IgG
(hemolytic disease of the newborn)
Passive anti-D IgG
anti-Rh
IgM
39. DIMERIC IgA
IgA dimers are in the highly vulnerable mucosal epithelia lining the
GI, respiratory, urinary and genital tracts, the eyes, nose and throat
(Transcytosis)
