UWorld_Immunology

Question 1

Characteristics of IgA deficiency

Answer 1

• due to failure of B cells to switch from IgM to IgA production
• recurrent sinus & GI infections
• ==> reaction to blood products due to presence of anti-IgA IgG in patient serum

Question 2

Characteristics of NK cells

Answer 2

• no CD3/4/8 on surface ==> express CD16 or CD56
• do not require thymus; present in athymic patients
• contain porphyrins & granzymes ==> apoptosis
• activated by INF-gamma & IL-12
• kill cells with decreased or absent MHC I on surface
  
  • e.g. tumor cells
• no antigen-recognition/memory

Question 3

Characteristics of Wiskott-Aldrich syndrome

Answer 3

• X-linked
• combined B & T cell disorder
• immunodeficiency
• eczema
• thrombocytopenia

Question 4

Characteristics of MHC Class I moleculues

Answer 4

• gene loci: HLA-A/B/C
• binds to: TCR & CD8 receptors
• expressed on all nucleated cells (except RBCs)
• Fxn
  
  • present endogenously synthesized antigens (e.g. viral)
  • CD 8+ cytotoxic T cells
• antigen loading
  
  • antigen loading onto MHC I in RER after delivery via TAP peptide trasnporter
• mode of transport to cell surface
  
  • B2 microglubulin

Question 5

Microscopic steps of inflammation

Answer 5

• margination
• rolling
• activation
• tight adhesion and crawling
• transmigration

Question 6

Key molecular components of rolling

Answer 6

• loose binding via sialyated carbohydrate groups
• @ PMNs = L-selection
• @ endothelial cells = E-selectin/P-selectin

Question 7

Key molecular components of tight adhesion and crawling

Answer 7

• CD18 beta 2 integrins (Mac-1 and LFA-1) bind to ICAMs on endothelial cells

Question 8

Key molecular components of transmigration

Answer 8

• PMNs squeeze between cells and out of vasculature
• migrate via integrin attachments and adherence to platelet endothelial cell adhesion molecule 1 (PECAM-1)

Question 9

Recurrent false positive RPR w/negative T. palludum immunoassay ==> dx?

Answer 9

• anti-phospholipid ab in lupus
• prolonged PTT no corrected by mixing
  
  • parodoxical b/c clotting risk = increased

Question 10

Causes of hyper-IgM

Answer 10

• absence of CD40 on T-lymphs or deficiency of enzyems that modify DNA in isotype switching

Question 11

Characteristics of polymyositis

Answer 11

• immune-mediated inflammatory myopathy ==> bilateral proximal m. weakness
• increased MHC I expression w/autoantigen presentation ==> CD8 infiltration and destruction of muscles
• increased serum CK and anti-Jo-1 antibodies