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USMLE Step 1 Immunology

Subjects : health-sciences, usmle-step-1

Instructions:

Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
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This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. Which HLA's are included in MHC I? MHC II?

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2. What are HEV? Where are they found? Where does the vasculature of the lymph node travel to?
It is a localized type III hypersensitivity reaction to an external antigen; localized instead of systemic; ?; intradermal injection of the antigen results in antibody production and antigen antibody complexes deposit in the skin
Immunoflourescent staining of tissue biopsies
Opsonize bacteria (for enhanced phagocytosis) - neutralize viruses (igG) - activate complement (igM and igG) - sensitize mast cells (igE)
High endothelial venules are post capillary cuboidal endothelial cells that contain specific adhesion molecules for lymphocytes with specific binders that allows for lymphocytes to drain out of the vasculature into the lymph node structure (this is h

3. What are MHC Class molecules (ie what macromolecule are they made out of)? what gene are responsible for MHC?
MHC I - CD16 - CD56
Glycoproteins; HLA
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils

4. What do mature naive B lymphocytes express?
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
TLR ad nuclear receptors
except hyperacute
IgM and IgD

5. What are some catalase positive organisms?
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
S. aureus - E. Coli - aspergillus
Fc

6. What is the clinical use for azathioprine?
Inferior mesenteric
Activates Th1 helper cells; Macrophages
IgE
...

7. in which immunodef order do you see a lot of pus? no pus?
Complement activation (active in both)
Defect in LFA 1 integrin (CD 18) protein on phagocytes (neutrophils!); recurrent bacterial infections - severe gingivitis - poor wound healing - absent pus formation - and delayed separation of the umbilicus; neutrophilia
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)
Th2; Th1

8. Which helper T cells' development is induced by IL 4? IL 12?
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis
Th2; Th1
Axillary
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy

9. What is the main function of IL 12? other than macrophages who else can release IL 12?
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
IgM and IgA

10. What portion of the lymph node is not well developed in DiGeorge Syndrome?
Paracortex
Cytokine IL 10 secreted by Th2
Interferon gamma; Th1
The patient could become cyanotic in the OR!

11. What are superantigens? give two examples.
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
First a B cell gets sensitized to an allergen - after sensitization - it gets induce by Th2 secreting IL4 to class switch from IgM to IgE - next time blood stream is exposed to allergen these antigens cross like IgEs on mast cells and result in chemi
Antimicrobial also secreted by CD8 and NK cells that induces apoptsosis
CROSS LINK Beta region on TCR of CD4 cells to the MHC class II on APCs this results in uncoordinated release of Interferon gamma from CD4 Th1 cells and subsequent release of IL1 - IL6 and TNF alpha from Macrophages --> toxic shock syndrome; s. pyogen

12. What is the most common selective Ig deficiency? What is the presentation?
IgM and IgA
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
Closed circuit where go directly to veins and open where squeeze out of capillary sinusoids and interact with either PALS or with macrophages in the cords of Billroth (for antigen immune function or for blood cleaning or for both) and squeeze back in
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2

13. What is the presentation of common variable immunodef? and What are the labs?
Not thymus - BM
Antihistone
Can be acquired in 20s -30s; increased risk of autoimmune disease - lymphoma - Sp infections; normal number of B cells and no plasma cells and immunoglobulin
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells

14. What type of side chains are found on Fc region of an antibody?
For some reason a mature naive B lymphocyte got away from tolerance and the result was a production an Ab on its surface with an Fab region that recognized the alpha 3 collagen subunit on the BM as non self. It then gets activated by a Th2 cell (enti
Antihistone
Carbohydrate
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)

15. which antibody is involved in the primary response or immediate response to an antigen?
An acidified endosome with the antigen fuses with the MHC which causes the release of the invariant chain Which is sitting in spot of antigen and stabilizing the MHC II
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith
IgM
MHC II - B7

16. What is the main cytokine released by T cells? What does it do
Induces fever - chemokine secretion to recruit - activates adhesion molecules; macrophages
...
IL 3; supports growth and differentiation of bone marrow stem cells
2 heavy chains and two light chains

17. What are the mediators that mast cells release?
IgM
S. aureus - E. Coli - aspergillus
Histamine (causes vasodilation) - leukotrienes (causes bronchoconstriction) - chemotaxins for eos - and heparin (increased blood flow needs to be anticoagulated!)
neutrophilia!

18. What is the clinical use for sirolimus? what should you combine it with?
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids
Fc
Not thymus - BM
By transcytosis

19. What is thrombopoietin used for?
Th cells fail to produce interferon gamma; a lot of IgE
Thrombocytopenia
Celiac
A B and T cell disorder; X linked recessive; progressive deletion of B and T cells; thrombocytopenic purpura - infections - eczema; high IgE and IgA but low IgM

20. What is wiskott aldrich syndrome? What is its mode of inheritance? What is the pathogenesis of disease? What is its triad of presentation? what labs does it present with?
A B and T cell disorder; X linked recessive; progressive deletion of B and T cells; thrombocytopenic purpura - infections - eczema; high IgE and IgA but low IgM
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy
IL 4 - 5 - 10 - 6
Periarteriolar lymphatic sheath in the white pulp that surround that dead end of the capillaries in the red pulp - contain T cells

21. What are the three types of lymphocytes?
Pernicious Anemia and Hashimotos
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein
B - T - and NK cells

22. What lymph node drains the lateral side of the dorsum of the foot?
lowest concentration
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants
Popliteal
Barrel hoop basement membrane fenestrations

23. What is the mechanism for sirolimus? what else it known as?
Binds to Mtor which (like tacrolimus and cyclosporine just in a different pathway) inhibits IL 2 production and thus t cell proliferation in response to IL 2 producton
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
Septicemia with neisseria; because at least you have C3 to act like a neutrophilic chemotactic and an acute phase reactant
Thrombocytopenia

24. Describe the capsular structure of a lymph node; What are the functions of the LN?
Into cortex and medulla; cortex is where immature T lymphocytes enter - at the corticomedullar junction is where positive and negative selection occur; and at the medulla is where the mature T lymphs - reticulin cells and hassalls corpuscles are (dea
MHC II - B7
T cell and antibody mediated vascular damage due to MHC non self being recognized as self by self lymphocytes and resulting in attack of the foreign antigens it presents (all of them); months to years after; no :(
Capsule of lymph node is made up of type III collagen (made by reticulin fibers!) - extension of this collagen extends into the splenic tissue as trabeculae; nonspecific filtration of lymph by Macrophages - Antibody production (via activation) - stor

25. What are the symptoms of serum sickness?
Cyclosporine - OKT3
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
encapsulated
Histamine; post capillary venules - vasodilation

26. What happens in a secondary follicle?
Fc
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
pentamer
Histamine; post capillary venules - vasodilation

27. What is epo used for?
Th2; Th1
Anemias (esp due to renal failure)
...
IgE

28. which type of immunity is slow but long lasting? as opposed to...
Capsule of lymph node is made up of type III collagen (made by reticulin fibers!) - extension of this collagen extends into the splenic tissue as trabeculae; nonspecific filtration of lymph by Macrophages - Antibody production (via activation) - stor
Active; passive - fast but short half life (3 weeks!)
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2
C5a

29. what results in symptoms of shock in an acute hemolytic transfusion reaction?
Negative nitroblue tetrazolium reduction test
Anti glutamate carboxylase and anti insulin
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock
TLR ad nuclear receptors

30. What is the toxicity of azathioprine?
Fc
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
...
delayed!

31. IgM can exist as a _______ also
pentamer
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
...
Recom IL 11; thrombocytopenia

32. which antibodies prevent antigens from binding mucosal surfaces?
Activates cytotoxic CD 8 T cells as second signal
Cytokine IL 10 secreted by Th2
IgA
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock

33. what characterizes an arthus reaction?
False! B cell class switching requires a second signal
Edema and necrosis in that region
IgE; by activating eosinophils
For some reason a mature naive B lymphocyte got away from tolerance and the result was a production an Ab on its surface with an Fab region that recognized the alpha 3 collagen subunit on the BM as non self. It then gets activated by a Th2 cell (enti

34. Only the _______ contribute to the Fc region
MS
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)
Opsonize bacteria (for enhanced phagocytosis) - neutralize viruses (igG) - activate complement (igM and igG) - sensitize mast cells (igE)
heavy chains

35. what prevents NK cells from killing normal cells if their default is to kill?
The igA found in breast milk
Antidesmoglein
Negative nitroblue tetrazolium reduction test
MHC class molecules bind to KIRS or CD94 to prevent killing

36. What is the pathogenesis of IgG AIHA ABO hemolytic disease of a newborn? describe what happens.
Macrophages - Dendritic cells - B cells
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
Alternative splicing of mRNA
Type II hypersensitivity - complement dependent resulting in phagocytosis of RBCs coated with C3b by fixed macrophages in the spleen; Group O mother has anti A - B - IgG Abs that cross placenta and attach to fetal blood group A or B RBCs

37. What are the cell surface proteins on NK cells?
MHC I - CD16 - CD56
cannot cross placenta
CRP - C3b - IgM
Acts as second signal on B cells to induce class switching to IgE and IgG

38. what cell surface proteins are on all APCs?
Superficial inguinal
High endothelial venules are post capillary cuboidal endothelial cells that contain specific adhesion molecules for lymphocytes with specific binders that allows for lymphocytes to drain out of the vasculature into the lymph node structure (this is h
IgM or IgG antibodies coat the antigen and result in activation of MAC complex via the classical pathway OR fixed macrophages in the spleen phagoctyose the opsonized (C3b or igG) antigens - ex penicillin reaction; IgM AIHA - anti B IgMs in a group A
MHC II - B7

39. What do multimeric antibodies require for assembly?
Carbohydrate
A j chain
MS - hay fever - SLE - goodpastures
Severe pyogenic infections early in life

40. What is the late phase reaction of anaphylaxis allergy? what mediates it?
Anti smooth muscle
Antidote for digoxin intoxication
Hours later (instead of minutes); instead of release of preformed mediators - mast cells synthesize PGs and LTs that mediate the late phase reaction (edema - inflammation - decreased airflow)
Receiving preformed Antibodies

41. Describe the Mannose Lectin pathway
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
...
Some microbial surfaces (only) have mannan binding lectin which activates a protease that cleaves C2 and C4 which combine to make C3. the rest follows the alternative pathway
pale central germinal centers

42. Which disease is associated with B8?
Rheumatic arthritis
Both decrease cd8 tcell prolif but one through mtor and the other through calcineurin (resp)
Graves
Opsonize bacteria (for enhanced phagocytosis) - neutralize viruses (igG) - activate complement (igM and igG) - sensitize mast cells (igE)

43. How fast does it occur?
The patient could become cyanotic in the OR!
DAF and C1 esterase inhibitor on cells prevent complement activation on their surfaces (microbial surfaces lack this)
A B and T cell disorder; X linked recessive; progressive deletion of B and T cells; thrombocytopenic purpura - infections - eczema; high IgE and IgA but low IgM
IgM

44. where do NK cells develop?
Severe pyogenic infections early in life
C3b; coating of a pathogen with molecules that promotes phagocytosis; IgG and CRP
Activates cytotoxic CD 8 T cells as second signal
Not thymus - BM

45. What lymph node drains the stomach?
Basophils! THey want IG E class switch!
Celiac
Type IV
Into cortex and medulla; cortex is where immature T lymphocytes enter - at the corticomedullar junction is where positive and negative selection occur; and at the medulla is where the mature T lymphs - reticulin cells and hassalls corpuscles are (dea

46. are Th cells involved in trapping of antigens of endotoxin/LPS?
Thrombocytopenia
No because no peptide fragment!
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency

47. What is digoxin immune Fab used for?
MHC I; from RER with help of the B2 microglobulin
S. aureus - E. Coli - aspergillus
Defect in LFA 1 integrin (CD 18) protein on phagocytes (neutrophils!); recurrent bacterial infections - severe gingivitis - poor wound healing - absent pus formation - and delayed separation of the umbilicus; neutrophilia
Antidote for digoxin intoxication

48. which antibodies can bind complement?
Found in the red pulp; contains the cords of billroth or the splenic parenchyma that have APCs/Macrophages that closely interact with the basement membrane of the vasculature and where RBCs squeeze through into the parenchyma and interact with Macrop
Activate macrophages
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
IgM and IgG

49. What does IL 4 do?
2 heavy chains and two light chains
A B and T cell disorder; X linked recessive; progressive deletion of B and T cells; thrombocytopenic purpura - infections - eczema; high IgE and IgA but low IgM
Acts as second signal on B cells to induce class switching to IgE and IgG
Inferior mesenteric

50. What is chronic mucocutaneous candidiasis d/t?
Not thymus - BM
T cell dysfunction
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids
T