Failures of host defense mechanisms
8 important questions on Failures of host defense mechanisms
SCID and defects in enzyme ADA
- ADA = adenosine --> inosine
- PNP = inosine --> hypoxanthine/ guanosine --> guanine
Accumulation of purine salvage intermediates are toxic to developing T and B cells --> lymphopenia (no white blood cells)
SCID and antigen receptor Omen
- mutation in RAG1 or RAG2 leads to arrest on lymphocyte development due to absence of positive selection of T and B cells because of V(D)J recombinant
Omenn syndrome = low levels of RAG activity results un limited T cell receptor gene recombination (No B cells)
Radiation-sensitive SCID = sensitivity to ionizing radiation through defects in ubiquitous DNA repair proteins involved in repairing DNA double-strands breaks
Defects in signaling T cel antigen receptor was
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Defects in thymic development digeorge
BLS or MHC deficiency = lack expression of MHC I or II
- MHC II
- CD4T cannot be selected positively
- antigen-presenting cell also lack MHC, so CD4T cannot be stimulated
- CD8T develop normally
- MHC I
- mutation in TAP, lead to that MHC cannot be transported to cell surface
APECED = Defects in AIRE lead to T cell repertoire that includes cell auto reactive to self antigens
Defects in B cell XLA
Bruton's XLA = In absence of BTK function, B cell maturation is largely arrested at pre-B cell stage, resulting in B cell deficiency
- Ig levels in newborn infants are primarily contributed by passive transfer from the mother
In females, which chromosome is active is random. Mature B cells always have the non defective X active
Defects in Tcell differentiation and impaired B cell cd40
- hyper IgM syndrome
- Tfh fail te active naive B cells resulting in failed class switching, somatic hypermutation and GC formation
- CD40 signaling is required for complete activation of DC and macrofagen
- deficient cross-talk between T cell and DC via CD40-CD40L can lead to lower co-stimulatory molecules
- not able to eliminate intracellular pathogen
Hyper IgE syndrome by STAT3 deficiency, play role in function of Tfh
Which deficiency, which pathogen
- mutation in STAT1 impair IFN-y signaling
- impaired IL-12 or IFN-y function
- IL-12p40 is shared by IL-12 and IL-23
- defects can lead to defective type 1 and type 3 immunity
TH17 or ILC3 - defense against fungi and extracellulair bacteria
Defects in cytolytic lymphocyte
Defects in exocytosis of cytotoxic granules
- antigen recognition leads to polarization of perforin-containing granules
- granules are transported to plasma membrane, where they dock through a RAB27a-dependent interaction
- docked vesicles are primed with Munc 13-4
- through munc18-2, fusion is initiated.
- content is release in target plasma membrane
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