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USMLE Step 1 Immunology

Subjects : health-sciences, usmle-step-1

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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. How do you test for type III hypersensitivity?
Paracortex
The igA found in breast milk
Immunoflourescent staining of tissue biopsies
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

2. What does interferon gamma do to be antiviral?
Paracortex; viral infection
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
Increases expression of MHC I and MHC II and also activates NK cells
Cyclosporine - OKT3

3. what else does interferon gamma do other than inducing ribonuclease production - activating NK cells - inducing increased MHC expression?
MS
Periarteriolar lymphatic sheath in the white pulp that surround that dead end of the capillaries in the red pulp - contain T cells
Activate macrophages
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

4. How do we use thymus dependent antigens to prevent infection from organisms that lack a peptide component?
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
Fc
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction
Anti smooth muscle

5. What are the main Cell surface proteins on T cells?
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L
Immunosuppression after kidney transplantation
Cross link
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

6. What are the autoantibodies for pernicious anemia?
Basophils! THey want IG E class switch!
Anti IF
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)
T cell dysfunction

7. What is colostrum?
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )
Anti viral and anti tumor
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
The igA found in breast milk

8. What is the clinical use for azathioprine?
Edema and necrosis in that region
In IgE AIHA- it results in MAC attack (remember IgE is not an opsonin!) - in IgG AIHA C3b (and IgG) opsonization results in phagocytosis by fixed macrophages in the spleen
...
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE

9. What is the clinical use of Muromonab?
isotype
CD56
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
Immunosuppression after kidney transplantation

10. Often bacteria are associated with being killed by humoral immunity. Name some bugs that require cell mediated immunity because they evade humoral response
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
In any situation where immunologically competent cells are transplanted into immunologically crippled recipient; graft rejects all the cells due to foreign proteins resulting in severe organ dysfunction
Thrombocytopenia
MS

11. What are the autoantibodies for primary biliary cirrhosis?
IgG
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)
If there is class switching and plasma cell production (that is when memory cells are produced)
Anti mitochondrial

12. What lymph node drains the upper limb?
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
Axillary
Anti Ach receptor
TLR ad nuclear receptors

13. What is the pathogenesis of acute transplant rejection? When does it occur?
Negative selection
Increases expression of MHC I and MHC II and also activates NK cells
heavy chains
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after

14. IgG...
opsonizes
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
CD21 on B cells (although there is T cell lymphocytosis in EBV)
Acts as second signal on B cells to induce class switching to IgE and IgG

15. Which is the most abundant antibody in blood?
Immune complex - Arthus reaction and Serum sickness; they are all a result of antibody- antigen complex deposition resulting in complement activation
Lymphocytes
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 :(
IgG

16. Which type of selection of thymic development provides central tolerance?
Negative selection
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein
DM type I
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

17. What lymph node drains the rectum (above the pectinate line)?
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis
isotype
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
Internal iliac

18. What is Aldesleukin? What is it used for
A recomb cytokine of IL 2; RCC and metastatic melanoma
MHC I - CD16 - CD56
MHC class molecules bind to KIRS or CD94 to prevent killing
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!

19. Name two endogenous pyrogens
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
Hemochromatosis
By transcytosis
IL 1 and IL 6

20. How does complement link innate and adaptive?
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill
Anti IF
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
The igA found in breast milk

21. How is the antigen loaded onto a MHC II?
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii
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
Coarse Faces - cold (noninflamed d/t inability to attract neutrophils) staph abscesses - retained primary teeth - high igE - dermatologic problems (eczema)
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)

22. What amine is the main chemical mediator released by mast cells? Where does it act What does it result in?
Paracortex; viral infection
Histamine; post capillary venules - vasodilation
Sinusitis - otitis media - pneumonia
Septicemia with neisseria; because at least you have C3 to act like a neutrophilic chemotactic and an acute phase reactant

23. What are the main cell surface proteins on B cells?
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7
Septicemia with neisseria; because at least you have C3 to act like a neutrophilic chemotactic and an acute phase reactant
Negative selection

24. other than mediating shock - what else does TNF alpha do? who releases it mainly?
Basophils! THey want IG E class switch!
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
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
Activates Th1 helper cells; Macrophages

25. Which is the main antibody that provides passive immunity to infants?
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids
2 heavy chains and two light chains
IgG
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

26. What are the main symptoms of T cell immunodeficiencies?
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!
IL 1 and IL 6
Negative!
Intracellular pathogens (acute and chronic viruses and virally induced cancers)

27. What does granulysin do?
Th2; Th1
Lack of MHC class I constant region which it binds or a nonspecific activation signal (TLR)
Antimicrobial also secreted by CD8 and NK cells that induces apoptsosis
Edema and necrosis in that region

28. What is the marginal zone of the spleen? what happens there?
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
IgA
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis

29. what mediates the type II hypersensitivity? What are the two different methods?
Antibody mediated cytotoxicity; either complement dependent or complement independent
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells
Histamine (causes vasodilation) - leukotrienes (causes bronchoconstriction) - chemotaxins for eos - and heparin (increased blood flow needs to be anticoagulated!)
Superficial inguinal

30. Which cytokines do Th2 release and For what?
TGF beta and IL 10
IL 4 - 5 - 10 - 6
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1
Rheumatic arthritis

31. What does IL 2 do?
isotype
Activates cytotoxic CD 8 T cells as second signal
Receiving preformed Antibodies
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

32. What is the symptoms involved in graft versus host disease? it What transplant cases does it usually occur? give an example
Cytokine IL 10 secreted by Th2
MHC I; from RER with help of the B2 microglobulin
Lack of MHC class I constant region which it binds or a nonspecific activation signal (TLR)
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

33. The alternative pathway is the only constutively...
neutrophilia!
MS
active complement pathway
isotype

34. Which helper T cells' development is induced by IL 4? IL 12?
TLR ad nuclear receptors
Th2; Th1
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)

35. So antibodies are the effectors for the humoral response. List some of their functions.
T cells react to the angtigen and activate leukocyted (macrophage acitivation)
By transcytosis
S. aureus - E. Coli - aspergillus
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization

36. What lymph node drains the sigmoid colon?
Type IV
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
DAF and C1 esterase inhibitor on cells prevent complement activation on their surfaces (microbial surfaces lack this)
Inferior mesenteric

37. What are the autoantibodies for polymyositis and dermatomyositis?
Macrophages - Dendritic cells - B cells
Anti Jo -1
IgM
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles

38. What are the three types of lymphocytes?
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
IgM and IgA
B - T - and NK cells
IL 4 - 5 - 10 - 6

39. What are the two signals required for B cell class switching? Which is the second signal?
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
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
Axillary

40. where do somatic hypermutation and class switching occur?
Influenza; antigenic shift; antigenic drift
In the germinal center of secondary follicles (In the paler center)
Soluble C3 spontaneously hydrolyzes spontaneously to C3b and opsonizes microbial and host cell surfaces and accumulates on surfaces; C3b activates C5 convertase which leads to MAC activation
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated

41. How fast does it occur?
Anti topoisomerase
The patient could become cyanotic in the OR!
Inferior mesenteric
Histamine; post capillary venules - vasodilation

42. which antibodies can bind complement?
IgM and IgG
Not thymus - BM
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
...

43. What is the presentation of common variable immunodef? and What are the labs?
TNF alpha and IL1
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening
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
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

44. What are MHC Class molecules (ie what macromolecule are they made out of)? what gene are responsible for MHC?
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
IL 3; supports growth and differentiation of bone marrow stem cells
Glycoproteins; HLA
Anti SS- A (anti RO) and Anti SS- B

45. What are the three types of APCs?
Macrophages - Dendritic cells - B cells
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
acute phase reactants
Active; passive - fast but short half life (3 weeks!)

46. what secretes IL 4?
Its a serine protease that activates apoptosis; NK and CD8
Anti mitochondrial
...
Basophils! THey want IG E class switch!

47. What are the two signals required for T cells? what happens after?
Cells that stil have weird parts of their membrane that macrophages usually bite off
Secretory component
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
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!

48. Describe complement dependent Type II hypersensitivity. Give an example.
Cells that stil have weird parts of their membrane that macrophages usually bite off
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L
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

49. What lymph node drains the breast?
Anti mitochondrial
Sinusitis - otitis media - pneumonia
Carbohydrate
Axillary

50. What are the autoantibodies for other vasculitides?
Remove encapsulated bacateria
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
Anti topoisomerase

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USMLE Step 1 Immunology

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