Point 1 to remember :-At
a basic level, IgM antibodies usually are associated with the
early onset phase of an infection (acute), while IgG is
generally associated with long-term immunity or reactivity towards a pathogen
(chronic).
Point 2
:to remember:- High avidity (AI ≥ 60%) means that Rubella
/ Toxopasma infection was acquired before 3 months ago, whereas
borderline avidity (50% < AI < 60%) means infection
at an indeterminate period, and low avidity (AI ≤ 50%) means that
the infection was acquired within the last 3 months.
Point 3:-to Remember: --
IgG and IgM are two types of antibodies that are found in
the blood. ... At a basic level, IgM antibodies
usually are associated with the early onset phase of an infection (acute),
while IgG is generally associated with long-term immunity or
reactivity towards a pathogen (chronic).
Point
4 to rememberLevels of antibodies :--Serum IgG
levels are usually less than 200 mg/dL, and IgM and IgA levels are
less than 20 mg/dL. Peripheral blood CD19+ B-cell counts are
commonly less than 0.1%..
Point
5 to remember? IgG and IgM are
two types of antibodies that are found in the blood and these
antibodies are part of the body’s immune system that is used
to identify, neutralize, and destroy foreign objects and organisms, such as
bacteria, parasites, and viruses.
Point
6 to remember? Which one appears first ?? At a basic level, IgM
antibodies usually are associated with the early onset phase of an infection
(acute), while IgG is generally associated with long-term immunity or
reactivity towards a pathogen (chronic)..
Point
7 to remember ::: In depth knowledge on
avidity(not to be read by G &O specialist):-Point 7 to remember? Antibody avidity describes
the strength with which an antibody binds to a complex antigen. Several methods
have been described for determining relative antibody avidity to different
types of antigens In EIA techniques,
the binding of antibody to the coated antigen may be prevented by competitive
inhibition using decreasing concentrations of free antigen or, more usually, by
eluting the antibody from the antigen by a dissociating agent, such as thiocyanate,
urea, or diethylamine.
Thiocyanate anion and
urea interfere with the antibody-antigen binding
primarily through disrupting the hydrophobic bonds; diethylamine is a
protein-denaturing agent. Two avidity assays based on pneumococcal EIA and
using sodium
thiocyanate elution have
been developed. Because the elution assays are based on dissociation of
antibody-antigen complexes of low avidity, they allow the ranking of the
antibodies by their avidity.
Point 8 to remember ::: In depth knowledge on
avidity(not to be read by G &O specialist):-Point 7 to remember? The
avidity of antibodies induced in infants after pneumococcal conjugate vaccination increases from postprimary samples to prebooster
samples and increases further over time.147,153,154 Experience
with Hib conjugate vaccines suggest that measurement of antibody avidity is
also useful in assessing the induction of memory.150 Therefore,
it has been suggested that avidity assays could be used to distinguish between
those who are primed for memory and those who are not.
Keith P. Klugman,
... Cynthia G. Whitney, in Plotkin's Vaccines
(Seventh Edition), 2018
Avidity
Antibody avidity describes
the strength with which an antibody binds to a complex antigen. Several methods
have been described for determining relative antibody avidity to different
types of antigens.157–162 In EIA techniques, the binding of antibody to the coated
antigen may be prevented by competitive inhibition using decreasing
concentrations of free antigen or, more usually, by eluting the antibody from
the antigen by a dissociating agent, such as thiocyanate, urea, or diethylamine.
Thiocyanate anion and urea interfere with the antibody-antigen binding primarily through disrupting the hydrophobic
bonds; diethylamine is a protein-denaturing agent. Two avidity assays based on
pneumococcal EIA and using sodium thiocyanate elution have been developed. Because the elution assays are
based on dissociation of antibody-antigen complexes of low avidity, they allow
the ranking of the antibodies by their avidity.
The avidity of antibodies induced in
infants after pneumococcal conjugate vaccination increases from postprimary samples to prebooster
samples and increases further over time.157,163,164 Experience
with Hib conjugate vaccines suggest that measurement of antibody avidity is
also useful in assessing the induction of memory.160
Appendix
FDG avidity in the appendix may be
physiologic, inflammatory, or malignant. Again, correlation with CT images can
help to discriminate physiologic FDG avidity from other causes. Appendiceal
wall thickening or mass may be seen on the CT component of PET/CT for primary
appendiceal malignancies (adenocarcinoma, cystadenocarcinomas, and
neuroendocrine tumors), lymphoma, and metastases. FDG avidity in the appendix
may be inflammatory. In patients with abdominal pain and an appendicolith on
CT, FDG PET/CT has even led to the diagnosis of appendicitis 
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