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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.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

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. Often bacteria are associated with being killed by humoral immunity. Name some bugs that require cell mediated immunity because they evade humoral response
False! B cell class switching requires a second signal
Antidote for digoxin intoxication
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7

2. What is a type I hypersensitivity reaction? What is atopic?
NK cells
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
carboxy terminal

3. What are the autoantibodies for hashimotos?
Antimicrosomal and antithyroglobulin
Negative nitroblue tetrazolium reduction test
IgM and IgD
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

4. What is the main function of interferons?
Anemias (esp due to renal failure)
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
Anti viral and anti tumor
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1

5. What is the pathogenesis of acute transplant rejection? When does it occur?
Its main effect is a defect in Ab opsonization for killing
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
secondary
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after

6. __________ are a part of the innate system.
NK cells
Cells that stil have weird parts of their membrane that macrophages usually bite off
Pernicious Anemia and Hashimotos
TLR ad nuclear receptors

7. give an example of how influenza does a major antigenic shift.
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance
Bind FcG for antibody dependent cellular cytotoxicity
RNA segment reassortment

8. What is the autoantibody for SLE that is nonspecific? Specific?
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
A - B - C; all the D's
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells

9. Type IV hypersensitivity is i...
IgA
IL 3; supports growth and differentiation of bone marrow stem cells
not Ab mediated
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

10. If the alternative pathway is constitively active - how come normal cells don't get attacked with MAC?
No! That is why they are different from T cells - they can recognize antigens in free solution; if a bug has a peptide fragment that a mature naive B cell recognizes it will bind to it and cause activation - it then gets activated into a plasma cell!
DAF and C1 esterase inhibitor on cells prevent complement activation on their surfaces (microbial surfaces lack this)
Liver! (they are proteins circulating in the blood)
Antimicrobial also secreted by CD8 and NK cells that induces apoptsosis

11. What is MHC II made out of? Where is it found? What does it bind to? What type of antigens does it present?
TNF alpha and IL1
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
Tetanus - Botulinum - HBV - Rabies
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak

12. after C3 spontaneously hydrolyzes to C3b and C3a - what happens to C3a?
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated
acute phase reactants

13. What is recomb gamma interferon used for?
Chronic granulomatous disease
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)
Bind FcG for antibody dependent cellular cytotoxicity

14. What lymph node drains the thigh?
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
Superficial inguinal
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
By transcytosis

15. What are the autoantibodies for scleroderma (CREST)? scleroderma diffuse?
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)
Macrophages - Dendritic cells - B cells
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)

16. What does interferon gamma do to be antiviral?
IgA
Its a serine protease that activates apoptosis; NK and CD8
Cytokine IL 10 secreted by Th2
Increases expression of MHC I and MHC II and also activates NK cells

17. Which cytokines do Th2 release and For what?
DM type I
Paracortex
Local infection/inflammation; infection of the ln itself; metastasis
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1

18. What is the main cytokine released by T cells? What does it do
Barrel hoop basement membrane fenestrations
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear
Active; passive - fast but short half life (3 weeks!)
IL 3; supports growth and differentiation of bone marrow stem cells

19. What do mature naive B lymphocytes express?
heavy chains
C5a
Carbohydrate
IgM and IgD

20. Which helper T cells' development is induced by IL 4? IL 12?
T cell activation; no with CD 4 or CD 8
Anti alpha subunit 3 of collagen on type IV bm
Th2; Th1
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

21. What are the autoantibodies for myasthenia gravis?
cannot cross placenta
Anti Ach receptor
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1
IgG

22. What is the common variable immunodeficiency ? How is it different from Brutons?
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
IgAs in mothers breast milk!
opsonizes
A recomb cytokine of IL 2; RCC and metastatic melanoma

23. What are the autoantibodies for type I diabetes mellitus?
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
A chemotactic factor for neutrophils
DM type I and RA
Anti glutamate carboxylase and anti insulin

24. other than C3a - what other complement acts as an anaphyloxin?
Axillary
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
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
C5a

25. Only the _______ contribute to the Fc region
Negative selection
Anti Ach receptor
Septicemia with neisseria; because at least you have C3 to act like a neutrophilic chemotactic and an acute phase reactant
heavy chains

26. Which disease is associated with HLA A3?
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
CD56
IgM
Hemochromatosis

27. can igG cross the placenta?
Superficial inguinal
Yes
Anti viral and anti tumor
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP

28. Name two endogenous pyrogens
Yes
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening
A - B - C; all the D's
IL 1 and IL 6

29. What is anergy? why does this occur?
Cross link
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance
Rheumatic arthritis
Lymphocytes

30. What are the mediators that mast cells release?
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE
All MHC 1/CD8
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)
Histamine (causes vasodilation) - leukotrienes (causes bronchoconstriction) - chemotaxins for eos - and heparin (increased blood flow needs to be anticoagulated!)

31. What is the main function of TNF alpha? How does it do this?
No because no peptide fragment!
pentamer
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
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak

32. What are the autoantibodies for pernicious anemia?
Cyclosporine - OKT3
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
Anti IF
Interferon gamma; Th1

33. What is the toxicity of azathioprine?
B - T - and NK cells
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E
Acts as second signal on B cells to induce class switching to IgE and IgG
...

34. Which diseases are associated with DR4?
Axillary
DM type I and RA
Increases expression of MHC I and MHC II and also activates NK cells
IgM and IgD

35. What is the presentation of hyperIgM syndrome?
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance
Severe pyogenic infections early in life
A j chain
Its a serine protease that activates apoptosis; NK and CD8

36. What is the late phase reaction of anaphylaxis allergy? what mediates it?
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
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)
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated

37. In thymic development - What is the positive selection? negative selections?
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
When you select for which MHC it will have; take out the lymphs that self react
Coarse Faces - cold (noninflamed d/t inability to attract neutrophils) staph abscesses - retained primary teeth - high igE - dermatologic problems (eczema)
Celiac

38. What does it mean if there are igM in the serum at birth?
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)
Negative!
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

39. What two ways do you test for a type 1 hypersensitivity reaction? what will you see?
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
type four
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
acute phase reactants

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

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41. What are the cell surface proteins on NK cells?
MHC I - CD16 - CD56
Interferon gamma; Th1
Anti mitochondrial
SP infections

42. Which are the only two antiinflammatory cytokines?
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
IgA
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
TGF beta and IL 10

43. What is muromonab - CD3 (OKT3)
T
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
T cell dysfunction
Monoclonal Ab to CD3- blocks cellular transduction and signaling of T cells

44. what cell surface proteins are on all APCs?
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
By transcytosis
MHC II - B7
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance

45. What amine is the main chemical mediator released by mast cells? Where does it act What does it result in?
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils
Histamine; post capillary venules - vasodilation
Local infection/inflammation; infection of the ln itself; metastasis

46. ________ regulate the cell mediated response.
IgE
carboxy terminal
Humoral
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy

47. What is the clinical use for sirolimus? what should you combine it with?
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids
Interferon gamma and IL 2
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

48. which B and T cell disorder presents with specifically low IgM?
Brain - eyes - placenta/fetus - testicles; because they can have an antigen in there and not get attacked by immune system because dont have contact with immune system via blood and lymph; if an infection occurs such that trauma results in exposure t
secondary
Increases expression of MHC I and MHC II and also activates NK cells
Wiskott Aldrich syndrome

49. How do endotoxin/LPS of gram negative bacteria stimulate the immune system if they do not have a peptide fragment?
They directly stimulate Macrophages by binding CD14; also the alternative complement pathway binds to these host surfaces and induces MAC complex; also TLRs exist for endotoxins; also IgM though not an opsonin can act as a pentamer and trap the antig
Hereditary angioedema; PNH
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
Kill them because they have CD16 on them that recognize the FcG portion

50. How fast does it occur?
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E
The patient could become cyanotic in the OR!
IL 5
carboxy terminal