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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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1. How is the antigen loaded onto a MHC II?
Alternative splicing of mRNA
encapsulated
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
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

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

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3. What are target cells?
Stimulate the liver to release acute phase reactants
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
secondary
Cells that stil have weird parts of their membrane that macrophages usually bite off

4. What is anergy? why does this occur?
IL 1 and IL 6
carboxy terminal
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
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance

5. 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?
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
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
pale central germinal centers

6. The Fc region is found on the...
If there is class switching and plasma cell production (that is when memory cells are produced)
IgE; by activating eosinophils
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)
carboxy terminal

7. What cytokines do macrophages release? who else can secrete IL 6? IL 12?
Immunosuppression after kidney transplantation
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
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
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

8. Which diseases are associated with DR4?
DM type I and RA
IgG
All MHC 1/CD8
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

9. What is three common causes of severe combined immunodef? What is the result of all three?
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency
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
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1

10. What is the symptoms involved in graft versus host disease? it What transplant cases does it usually occur? give an example
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells
Anti IF
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
Para aortic

11. What are the T cell functions?
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis
MHC I - CD16 - CD56
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated

12. What are the function of B cells?
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
DM type I
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi

13. What is epo used for?
Popliteal
Histamine; post capillary venules - vasodilation
pentamer
Anemias (esp due to renal failure)

14. What is the pathogenesis of chronic transplant rejection? When does it occur? is it reversible?
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
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)
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 :(
T

15. What are the two signals required for B cell class switching? Which is the second signal?
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
Fc
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
acute phase reactants

16. What is a factor that is a predictor for a bad transplantation?
Anti topoisomerase
Secretory component
Monoclonal Ab to CD3- blocks cellular transduction and signaling of T cells
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs

17. after C3 spontaneously hydrolyzes to C3b and C3a - what happens to C3a?
Activates cytotoxic CD 8 T cells as second signal
Cyclosporine - OKT3
A j chain
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.

18. What is passive immunity?
Receiving preformed Antibodies
Activates cytotoxic CD 8 T cells as second signal
T cell precursor
Lymphocytes

19. A lymph node is a ________ lymphoid organ.
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
secondary
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7

20. What is the monoclonal antibody to IL2 on activated T cells? What is it used for?
DM type I and RA
Daclizumab; prevent ACUTE rejection of renal transplant
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
isotype

21. What lymph node drains the lateral side of the dorsum of the foot?
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )
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
MS - hay fever - SLE - goodpastures
Popliteal

22. How do you test for chronic granulomatous disease?
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak
Negative nitroblue tetrazolium reduction test
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
IgM and IgG

23. Often bacteria are associated with being killed by humoral immunity. Name some bugs that require cell mediated immunity because they evade humoral response
T cell dysfunction
Aut. Dominant; C1 esterase inhibitor deficiency resulting in continued C1 which results in increased C2 and C4 cleavage products which have anaphyltoxic activity and result in swelling of face and oropharynx
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
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

24. What does IL 4 do?
Acts as second signal on B cells to induce class switching to IgE and IgG
Antimicrosomal and antithyroglobulin
CD56
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)

25. What happens in a secondary follicle?
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
Hemochromatosis
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated

26. which interleukin receptor is required for NK development? activation?
IL 15; IL 12 - interferon Beta and interferon alpha
IgM and IgA
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
Sinusitis - otitis media - pneumonia

27. What are the cell surface proteins on NK cells?
IL 4 - 5 - 10 - 6
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
MHC I - CD16 - CD56

28. Which antibodies can be multimeric?
Antimicrosomal and antithyroglobulin
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
IgM and IgA
S. aureus - E. Coli - aspergillus

29. What is MHC II made out of? Where is it found? What does it bind to? What type of antigens does it present?
Hereditary angioedema; PNH
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)
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA

30. which cytokine inhibits TH2 cells? secreted by who?
By transcytosis
Periarteriolar lymphatic sheath in the white pulp that surround that dead end of the capillaries in the red pulp - contain T cells
Interferon gamma; Th1
Aut. Dominant; C1 esterase inhibitor deficiency resulting in continued C1 which results in increased C2 and C4 cleavage products which have anaphyltoxic activity and result in swelling of face and oropharynx

31. Describe the Mannose Lectin pathway
Normal pro B (CD 19 +) - no mature B cells results in decreased total B cell level - and decreased amount of immunoglobulins in each class
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages
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
Antimicrobial also secreted by CD8 and NK cells that induces apoptsosis

32. What is the main cytokine that activates eosinophils?
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 :(
Para aortic
IL 5
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

33. What is the cause of thymic aplasia? What is its presentation? What are the labs?
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
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
cannot cross placenta
Antidote for digoxin intoxication

34. What are HEV? Where are they found? Where does the vasculature of the lymph node travel to?
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
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
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
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

35. What is the pathogenesis of chronic granulomatous disease; What is the presentation? What is the labs?
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)
Hereditary angioedema; PNH
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
Interferon gamma; Th1

36. What are the autoantibodies for hashimotos?
Increases expression of MHC I and MHC II and also activates NK cells
Anti TSh receptor
Antimicrosomal and antithyroglobulin
Paracortex; viral infection

37. What does IL 2 do?
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
Activates cytotoxic CD 8 T cells as second signal
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
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

38. From where do cytokines come from?
Secretory component
Lymphocytes
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
T cells react to the angtigen and activate leukocyted (macrophage acitivation)

39. 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)?
Paracortex
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
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
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage

40. What amine is the main chemical mediator released by mast cells? Where does it act What does it result in?
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow
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
Histamine; post capillary venules - vasodilation
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells

41. What are the autoantibodies for polymyositis and dermatomyositis?
...
Not thymus - BM
Anti Jo -1
Kill them because they have CD16 on them that recognize the FcG portion

42. What does granzyme do? who secretes it?
Its a serine protease that activates apoptosis; NK and CD8
From self; from identical twin or clone; from nonidentical individual of same species; from different species; fetus; pig valve
Both decrease cd8 tcell prolif but one through mtor and the other through calcineurin (resp)
Anti viral and anti tumor

43. What is the pathogenesis of a hypersensitivity reaction?
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
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
Negative nitroblue tetrazolium reduction test
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic

44. 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?
SP infections
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
Anti SS- A (anti RO) and Anti SS- B
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)

45. What is the thymus ? Where is it located? is it encapsulated? How many lobes does it have?
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)
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
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L

46. What is the clinical use for sirolimus? what should you combine it with?
IgG
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids
False! B cell class switching requires a second signal

47. What type of cells do NK cells attack? with What tools? by necrosis or apoptosis?
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis
Monoclonal Ab to CD3- blocks cellular transduction and signaling of T cells
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy

48. What is the result of an IL 12 deficiency? What is the presentation? What are the labs?
CRP - C3b - IgM
Complement activation (active in both)
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!

49. What are the autoantibodies for pemphigus bulgaris?
Alternative splicing of mRNA
...
Antidesmoglein
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak

50. Only the _______ contribute to the Fc region
By transcytosis
Graves
heavy chains
IgE