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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. Describe the capsular structure of a lymph node; What are the functions of the LN?
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
Superficial inguinal
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
IgM and IgD

2. Type Iv hypersensitivity is...
delayed!
Superficial inguinal
Type III hypersensitivity where an exogenous antigen results in a systemic antigen antibody complex disease (takes around 5 days after exposure for the Abs to develop); immune complexes then fix in tissue and activate complement resulting in tissue d
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids

3. What is the presentation of scid? treatment?
T cell precursor
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
isotype

4. What happens when a T helper cell in the paracortical section encounters an antigen? a cytotoxic t cell? a B cell in the cortical section?
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
B - T - and NK cells
An antigen encounter (presented by APC for Th2) with Th2 will result in it to go to the cortical section and help with B cell activation; Cytotoxic T cell will enter vasculature/efferent lymph to go kill; B cell will wait for Th2 for activation and t
Delayed type hypersensitivity

5. What is the main cytokine that activates eosinophils?
IgG
IgG
IL 5
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

6. A lymph node is a ________ lymphoid organ.
secondary
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
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
All MHC 1/CD8

7. To what portion of the Antibody do the complements bind?
Fc
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)
Digeorge syndrome - 22q11 deletion resulting in failure to develop 3rd and 4th pharyngeal pouches; cardiac and great vessel congenital defects - tetany from hypocalcemia - recurrent viral/fungal infections from T cell deficiency; hypoPTH - hypoCa - a

8. Which Thelper cell activated Macrophages? by secreting what? what else does Th1 secrete? For what?
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells
Both decrease cd8 tcell prolif but one through mtor and the other through calcineurin (resp)
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2

9. where do NK cells develop?
Not thymus - BM
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants
C3b; coating of a pathogen with molecules that promotes phagocytosis; IgG and CRP
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1

10. which type of immunity is slow but long lasting? as opposed to...
Graves
Active; passive - fast but short half life (3 weeks!)
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith

11. How does complement link innate and adaptive?
mesenchymal
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith
Antidote for digoxin intoxication
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill

12. What are the two signals required for B cell class switching? Which is the second signal?
Macrophages - Dendritic cells - B cells
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
Immunoflourescent staining of tissue biopsies
IgA

13. The lymphocytes are ________ origin
Stimulate the liver to release acute phase reactants
Pernicious Anemia and Hashimotos
Thrombocytopenia
mesenchymal

14. What cytokines to Th2 secrete?
IL 3; supports growth and differentiation of bone marrow stem cells
IL 4 - 5 - 10 - 6
TGF beta and IL 10
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens

15. What lymph node drains the thigh?
IgE
Give a vaccine with a peptide comp from it that the cell mediated immunity otherwise cant get to! like h.influenzae vaccine. then class switching and memory response can occur
C5a
Superficial inguinal

16. What lymph node drains the scrotum?
Th2; Th1
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
A - B - C; all the D's
Superficial inguinal

17. Other than stimulating fever - what else does IL 6 do?
Axillary
Stimulate the liver to release acute phase reactants
MHC class molecules bind to KIRS or CD94 to prevent killing
Th cells fail to produce interferon gamma; a lot of IgE

18. What is the pathogenesis of chronic transplant rejection? When does it occur? is it reversible?
Monoclonal Ab to CD3- blocks cellular transduction and signaling of T cells
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 :(
Defect in B cell maturation; idiopathic - presents at older age and normal number of B cells and hyperplastic germinal centers because B cells can be activated but can not produce Abs
Graves

19. What is the toxicity of muromonab?
Para aortic
CD56
T cell precursor
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction

20. Which MHC presents intracellular peptides? how so?
active complement pathway
MHC I; from RER with help of the B2 microglobulin
Steroid responsive nephrotic syndrome
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens

21. what characterizes an arthus reaction?
Yes
Edema and necrosis in that region
IgE
dimer

22. What is a factor that is a predictor for a bad transplantation?
Histamine (causes vasodilation) - leukotrienes (causes bronchoconstriction) - chemotaxins for eos - and heparin (increased blood flow needs to be anticoagulated!)
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs
A chemotactic factor for neutrophils
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation

23. What are the autoantibodies for myasthenia gravis?
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill
except hyperacute
Anti Ach receptor
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp

24. Which antibody mediates immunity to worms? how?
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage
IgE; by activating eosinophils
SP infections
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency

25. Describe the Mannose Lectin pathway
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
...
IL 4
MHC class molecules bind to KIRS or CD94 to prevent killing

26. How fast does it occur?
carboxy terminal
Stimulate the liver to release acute phase reactants
The patient could become cyanotic in the OR!
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis

27. what results in symptoms of shock in an acute hemolytic transfusion reaction?
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi

28. All transplant rejections - _____________ are mediated by Type IV hypersensitivity
The igA found in breast milk
except hyperacute
Its a serine protease that activates apoptosis; NK and CD8
MAC (membrane attack complex) Which is activated by C5b - C9 and results in lysis and cytoxicity by creating pores in the target membrane; encapsulated organisms (S. pnuemonia - H.influenzae - B perfussis for example) and other organisms with non pep

29. other than eat and bite RBCs what else do Macrophages of spleen do>
1) VJ light chain random creation 2) VDJ (heavy chain) random creation 3) random combination of light with heavy 4) somatic hypermutation (high frequency mutating that occurs on activation) 5) terminal deoxynucleotidyl transferase (TDT) random additi
Remove encapsulated bacateria
Barrel hoop basement membrane fenestrations
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E

30. IgM can fix complement but...
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE
Antidote for digoxin intoxication
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak
cannot cross placenta

31. What are C1 - C2 - C3 - C4 important for?
Anemias (esp due to renal failure)
Viral neutralization of igM and IgG!
Anti topoisomerase
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)

32. Describe the interstitial tissue of a spleen including the sinuses. What type of cells are found in the four structures (cortex - paracortex - medulla and sinuses)?
The interstitial tissue of a lymph node is structured into the cortex on the outside Which is densely cellular which transitions into the paracortex Which is less dense and then the medulla Which is least dense. The cells that inhabit these tissues a
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
secondary
Severe pyogenic infections early in life

33. Which diseases are associated with DR5?
Pernicious Anemia and Hashimotos
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7
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
IgE

34. What is the main function of IL 8?
T cell precursor
Anti alpha subunit 3 of collagen on type IV bm
A chemotactic factor for neutrophils
MHC I - CD16 - CD56

35. What is the pathogenesis of HyperIgE syndrome? What are the labs?
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
Th cells fail to produce interferon gamma; a lot of IgE
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
Negative selection

36. describe the pathogenesis of delayed type IV hypersensitivity
neutrophilia!
T cells react to the angtigen and activate leukocyted (macrophage acitivation)
Anti glutamate carboxylase and anti insulin
cannot cross placenta

37. What is the general structure of an Ab?
2 heavy chains and two light chains
Activate macrophages
Anti IF
Immunoflourescent staining of tissue biopsies

38. What are the autoantibodies for polymyositis and dermatomyositis?
Anti Jo -1
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)
Antihistone

39. What is the end result of complement activation? what bugs are this important for? through what pathway and why?
Anemias (esp due to renal failure)
MAC (membrane attack complex) Which is activated by C5b - C9 and results in lysis and cytoxicity by creating pores in the target membrane; encapsulated organisms (S. pnuemonia - H.influenzae - B perfussis for example) and other organisms with non pep
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear
Negative nitroblue tetrazolium reduction test

40. What are MHC's necessary for? By themselves?
The patient could become cyanotic in the OR!
T cell activation; no with CD 4 or CD 8
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)
Barrel hoop basement membrane fenestrations

41. What is the defect in Leukocyte adhesion defect? What is the presentation? What are the labs?
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
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic

42. What is oprelevkin? and What is it used for?
Maculopapular rash (palm - soles - back - neck) - jaundice with bile duct necrosis - hepatosplenomegaly - diarrhea; bone marrow and liver transplants (rich with lymphocytes); SCID patient receiving whole blood transfusion
Recom IL 11; thrombocytopenia
T
Activate macrophages

43. DTH (delayed type hypersensitivity) is the ________ of a PPD reaction
Anti glutamate carboxylase and anti insulin
pathogenesis
NK cells
Opsonize bacteria (for enhanced phagocytosis) - neutralize viruses (igG) - activate complement (igM and igG) - sensitize mast cells (igE)

44. What is thrombopoietin used for?
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata
Superficial inguinal
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
Thrombocytopenia

45. what cell surface marker is used for NK cells as it is unique to them?
CD56
Hereditary angioedema; PNH
Anti viral and anti tumor
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow

46. What is MHC II made out of? Where is it found? What does it bind to? What type of antigens does it present?
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
Interferon gamma; Th1

47. Describe the complement independent Type II hypersenstivity reaction. Give an example.
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated
Septicemia with neisseria; because at least you have C3 to act like a neutrophilic chemotactic and an acute phase reactant
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear

48. which immunodeficiency presents with delayed separation of the umbilicus? ataxia? telangiectasia?albinism? anaphylaxis on exposure to blood products with IgA? tetany?retained primary teeth? peripheral neuropathy?
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
A j chain
not Ab mediated
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages

49. What are the T cell functions?
Receiving preformed Antibodies
Tetanus - Botulinum - HBV - Rabies
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection

50. What are the autoantibodies for systemic sclerosis?
Secretory component
CD21 on B cells (although there is T cell lymphocytosis in EBV)
Anti topoisomerase
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