Immunodeficiencies II: Primary Deficiencies of Adaptive Immunity Flashcards
review pg 2
2
defect in x linked hyper IgM is not defect in B cell, defect is
CD40L mutation or deletion that compromises B cell/T cell interaction
humoral immunodeficiency can be caused by
b cell defect or t cell defect
intrinsic to b cell humora immunodeficiency:
XLA Selective IgA deficiency CVID Immunoglobulin IgG subclass deficiencies Transient hypogammaglobulinemia of infancy
X linked agammaglobulinemia (XLA0 is also known as
bruton’s agammaglobulinemia
CVID stands for
common variable immunodeficiency
intrinsic to t cell humoral immunodeficiency:
X-linked hyper-IgM syndrome
draw out antibodies and infants graph
pg 6
neonate is protected at birtha nd for 6 months by passively transferred
IgG from mother
what is the only isotype that can cross placenta
IgG
at time of birth baby has what levels of IgG
adult levels (of its moms IgG)
first immunoglobulin that the baby will make
IgM
at birth the baby starts to make its own
IgG
before birth baby makes what Ig?
M and A
features of pts with b cell deficiencies
recurrent respiratory infections and streptoccemia
organisms that predominate infections for b cell deficienceis:
Streptococci, Staphylococci and Haemophilus spp.
vast majority of viral infections are controlled how well through individuals with no b cell
pretty well - t cell will take care of on its own pretty well
infants with primary immunodeficiencies will not present with symptoms before
6-9 motnhs b/c they whave moms IgG
agammaglobulinema means
deficiency in ability to make antibodies
when does XLA present
6-8 months
common to have pneumonia by 2-3 yo. and recurrent upper respiratory tract infections that may never completely resolve and may have measles and be able to get rid of it, in what disease
XLA
why do XLA pts not have tonsils
tonsil are greater than 90% b cells, so no b cells, no tonsils
why does XLA not have lymphadenopathy
no folicles expanding into secondary and germinal centers, so no enlareged lymph nodes
serum levels for pt with XLA
IgM not detectable
IgA and IgG low
tonxilar node of pt with XLA
no b cells so just connective tissue
flow cytommetry of pt with XLA
no b cells so no CD19 marker pg 14
XHIGM is due to defect in
t cell
defect in XHIGM is in
CD40L
XHIGM stands for
X-linked Hyper-IgM
CD40L is also known as
CD154
MOI for XHIGM
x linked recessive
activation of macrophages will be defective in XHIGM why
b/c the Cd40/40L is needed for activation of macrophages
neutropenia is sign of
XHIGM
neutropenia is probably due to what in XHIGM
neutrophils exhausted, they are doing so much work b/c they don’t have IgG to help them out so they exhaust themselves faster
all fungal infections require
cell mediated response
pts with XHIGM are risk for getting
Recurrent upper and lower respiratory infections with bacteria, Pneumocystis jiroveci, CMV, Cryptococcus
fungi cannot be controlled
cluse to XHIGm
boy with hypogammaglobulinemia wit low or absent IgG and IgA with normal or elevated IgM
what is treatment for XHIGM
IGIV and anti-fungals
no live virus vaccines
bone marrow transplanation
why would somebody with deficiecny in CD40L not have follicels or germinal centers
consequence of first t cell b cell interaction - it will not happen without CD40/CD40L interaction so no proliferating b cells os no follicular follicles or germinal centers
what is whole purpose of germinal center reaction
somatic hypermutation to increase affinity of antibody
what would happen in CD40L deficiency in regards to somatic hypermutation
little to none, the first interaction depdent on CD40L is not going to happen
review pg 18
18
CD40L only expressed on T cells after
activation - and then transiently
t ells have to be ____ to express CD40L
activated
CD25 is a marker of
activated t cells
CD25 is
alpha chain of IL-2 receptor
it converts IL-2 to high affinity IL2
how do you know t cells are activated when you do flow cytometry
look for CD25 b/c it is marker of activated t cells
review pg 19
19
lymph node with hyper-IgM vs. not
no germinal centers in pt with hyper-IgM
autosomal form of hyper-IgM is usually caused by
AID deficiency
AID is required for
class switching
defect in function of AID causes
most common autosomal recessive form of hyper-IgM syndrom
HIGM2 is
autosomal recessive form of Hyper-IgM syndrom with lack of AID
AID satnds for
Activation-Induced Cytidine Deaminase
three major abnormalities characterized by AID deficiency:
- lack of immunoglobulin somatic hypermutations
- the absence of immunoglobulin class switch recombination
- lymph node hyperplasia caused by the presence of giant germinal centers.
HIGM2 from x linked - what are they distinguished by
HIGM2 has giant germinal centers
why does HIGM2 have giant germinal centers?
it will have the first b cell t cell interaction and they proliferate like crazy. there is no defect in CD40L here so b cells will go into follicel and proliferate, but they can’t mtuate the rearranged VJ or VDJ so no b cell has advantage over the other, they won’t increase affinty so nobody is outcompeting, so you get giant follicles
in the x linked version they won’t proliferate
selective IgA deficiency is
The severe deficiency or total absence of IgA both serum and secretory IgA.
what is most common of primary immunodeficiency
selective IgA deficiency
majority of individuals with selective IgA deficiency defect is unknown but there are genes associated
:)
b lymphocytes appear normal in selective IgA deficiency but do not
mature into IgA producing plasma cells
selective IgA deficiency most common in indviiduals with
european descent
how does one get selective IgA deficiency
familial, can also be acquired by measles or viral infection
what is weak in selective IgA deficiency
Mucosal defenses weakened; infections in respiratory, GI, urogenital tracts common.
how do pts with selective IgA deficiency present
Asymptomatic to symptomatic: patients present with recurrent sinopulmonary infections and diarrhea
NOTECARD PG 23
23
CVID stands for
Common Variable Immunodeficiency
CVID is:
CVID is a disorder characterized by low levels of serum immunoglobulins and increased susceptibility to chronic, recurrent sinopulmonary infections. Relatively “common” and degree and type of deficiency is “variable” from patient to patient.
unlike other primary Ig deficiencies the presentation of CVID is frequently
much later in life - early adulthood (most others present as babies)
treatment of pts with CVID
antibiotics, intravenous IG
B cell numbers in CVID
normal
T cells in CVID
normal
B cells are normal in CVID but
they decrease with time
the genetic defects in CVID all involve
roles in b cell and plasma cell survival and isotype switch
individuals with CVID have decreased wht in b cells
decreased isotyped switching and decreased memory cells for b cells
why do you get IgG levels at all (or any Ig) with XLA?
depends on how bad the mutation is and how inactivating that mutation is
XLA is what MOI
x linked recessive
male or female more likely to get XLA
male
peripheral blood lymphocytes from female carriers show skewed, or non random x chromosome inactivation, why?
it’s not really non-random in the b cell lineage - any b cell that has inactivated the x chrom that has the functional BTK is not going to make it through b ccell development, so the only ones that make it htrough the periphery in carriers are the ones that have inactivated the x chrom that carriers the effective allele. so it looks like non-random x chrom activation - during b cell development it’s not random - its chosen b/c they are the only ones that will make it
if mutation is totally inactiativating in XLA what will youdetect in serum
no b cells and no Ig
what is the marker of B cells
CD19
CD19+ is a marker of
b cells
flow cytommetry to look for CD19+ cells in pts with XLA you won’t find them in individuals where:
tyrosine kinase mutation is totally inactivating
where is block in b cell maturation in XLA
pre-b cell stage
what are t cell levels in pt with XLA
normal
should pts with XLA receive live vaccines
no
when will pts with XLA show symptoms
once mothers igG is below protective threshold
draw out b cell maturation in bone marrow
pg 10
need stem cell factor binding to what in b cell maturation in bone marrow
ckit
what does IL-7 need to bind to in b cell maturation in bone marrow
IL-7R
what is required for rearrangement in b cell
RAG1 and RAG2
RSS
Tdt
what does Tdt add
N nucleotides
block in b cell development in XLA is at
pre b cell stage
pre B cell receptor is
IgM (mu heavy chain) with surrogate light chain
to get beyond pre b cell receptor you need to do what
tell the cell that the pre b cell receptor works
signaling through the pre b cell receptor is dependent on
BTK
BTK stands for
bruton’s tyrosine kinase (what is mutated in XLA)
why can the cell not go beyond pre b cell in XLA
the BTK is mutated and that is what is needed to tell the cell that the pre b cell receptor works
consequences of signaling through the pre b cell receptor
exclude further rearrangement at heavy chain - allelic exlcusion
proliferation to make most of heavy chain you have
generate light chain - initaite VJ to join
the signaling part associated with the b cell receptor is
Igbeta and Igalpha ad ITAM
what is the CD for Igbeta
CD79b
what is the CD for Igalpha
CD79a
what besdies Btk can be defective/mutated in autosomal recessive forms of agamaglobinemia
mutations in Igalpa or Igbeta
lambda 5 - component of surrogate light chain
review pg 12, female non random x chrom inactivation for XLA
12
in female carrier of XLA if you sample serum, the only b cells you will find have:
they are the ones that silenced the defective BTK so only the working BTK cells will be expressed in the periphery, the other ones wouldn’t make it out
deficiency in one or two IgG sublcasses where other immunoglobulin levels are normal and suffer recurrent infection is what deficiency
selective IgG subclass
Selective IgG Subclass Deficiency is less severe than
XLA & CVID
predominant IgG sublcass
IgG1
IgG2 deficiency is common in
children
IgG3 deficiency is common in
adults
ppl deffecicent in IgG4 often also deficient in
IgG2
deficiency of IgG1 comomon in
trick - not common, it is rare
family members with IgG subclass deficiency can also have
selective IgA deficiency or CVID
diagnosis of Selective IgG Subclass Deficiency
History of recurrent infections of ears, sinuses, bronchi and /or lungs.
Low level for age of IgG subclass and normal levels of other immunoglobulins.
Normal numbers of B and T cells
Normal function: DTH and lymphocyte stimulation
IgG2 subclass deficiency: unable to produce antibodies when immunized with polysaccharide vaccines
Some children outgrow IgG subclass deficiency
treatment of selective IgG sublcass def.
antibiotics for infections or prophylactically
what is level of IgG sublcass for IgG subclass deficiency
low level for age
what is level of Ig besides IgG in IgG subclass deficeincy
normal
IgG2 dominates the response against
capsular polysaccharides
if there is IgG2 subclass deficiency, what is the major reason why this is bad
they can’t produce antibodies when immunized with polysaccharide vaccines
most dominant IgG
1
least dominant IgG
4
what IgG take longest to reach adult levels
IgG2 and 4
IgG1 and 3 are most efficeicnt to
activate complement - most efficient is 3
IgG2 can compensate for
1 and 3, can fill in for response to conjugate polysaccharide vaccine