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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 TCR MHC system is important for viral immunity? neoplastic? donor graft cells?
All MHC 1/CD8
Severe pyogenic infections early in life
Its a serine protease that activates apoptosis; NK and CD8
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive

2. other than C3a - what other complement acts as an anaphyloxin?
C5a
RNA segment reassortment
Edema and necrosis in that region
Stimulate the liver to release acute phase reactants

3. which cytokine inhibits TH2 cells? secreted by who?
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
IL 15; IL 12 - interferon Beta and interferon alpha
Superficial inguinal
Interferon gamma; Th1

4. Monomer in circulation - ___ when secreted
Thrombocytopenia
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
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
dimer

5. How does complement link innate and adaptive?
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill
encapsulated
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)
Previous transfusion; pregnant woman whose fetus had paternal antigens

6. What is the clinical use for sirolimus? what should you combine it with?
Sinusitis - otitis media - pneumonia
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
If there is class switching and plasma cell production (that is when memory cells are produced)

7. what bacteria are a splenectomy patient most susceptible to? why?
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
N. meningitidis - H. influenzae - S. pneumonia - Salmonella d/t lack of C3b opsonization for MAC d/t lack of complement activation d/t lack of IgM; MAC is needed by encapsulated avoid by humoral and cell mediated through their capsule
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
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

8. How do you test for type III hypersensitivity?
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith
acute phase reactants
Immunoflourescent staining of tissue biopsies
Fab portion

9. Which is the most abundant antibody in blood?
IgG
heavy chains
Normal pro B (CD 19 +) - no mature B cells results in decreased total B cell level - and decreased amount of immunoglobulins in each class
Axillary

10. Describe complement dependent Type II hypersensitivity. Give an example.
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage
Coarse Faces - cold (noninflamed d/t inability to attract neutrophils) staph abscesses - retained primary teeth - high igE - dermatologic problems (eczema)
encapsulated
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

11. What is the marginal zone of the spleen? what happens there?
Antibody mediated cytotoxicity; either complement dependent or complement independent
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
Acts as second signal on B cells to induce class switching to IgE and IgG
B - T - and NK cells

12. What are the three types of Type III hypersensitivity ? What is the common mechanism between them?
Immune complex - Arthus reaction and Serum sickness; they are all a result of antibody- antigen complex deposition resulting in complement activation
IgM and IgG
Alternative splicing of mRNA
isotype

13. For which toxins are preformed antibodies (passive) given?
Cells that stil have weird parts of their membrane that macrophages usually bite off
Negative selection
Tetanus - Botulinum - HBV - Rabies
DM type I and RA

14. What is the end result of complement activation? what bugs are this important for? through what pathway and why?
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
IL 3; supports growth and differentiation of bone marrow stem cells
Paracortex
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

15. which type of immunity is slow but long lasting? as opposed to...
IgM and IgA
SP infections
Active; passive - fast but short half life (3 weeks!)
The patient could become cyanotic in the OR!

16. What is the thymus ? Where is it located? is it encapsulated? How many lobes does it have?
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
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
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
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2

17. What is recomb gamma interferon used for?
CD56
When you select for which MHC it will have; take out the lymphs that self react
Chronic granulomatous disease
Increases expression of MHC I and MHC II and also activates NK cells

18. What is the cause of thymic aplasia? What is its presentation? What are the labs?
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
C3b; coating of a pathogen with molecules that promotes phagocytosis; IgG and CRP
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
N. meningitidis - H. influenzae - S. pneumonia - Salmonella d/t lack of C3b opsonization for MAC d/t lack of complement activation d/t lack of IgM; MAC is needed by encapsulated avoid by humoral and cell mediated through their capsule

19. What cytokines do macrophages release? who else can secrete IL 6? IL 12?
RNA segment reassortment
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
Liver! (they are proteins circulating in the blood)
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

20. 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?
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
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
Influenza; antigenic shift; antigenic drift
lowest concentration

21. What bugs can actually infect the lymph node itself?
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
MHC I; from RER with help of the B2 microglobulin

22. How is i Th1 helper cell inhibited?
Cytokine IL 10 secreted by Th2
Bind FcG for antibody dependent cellular cytotoxicity
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction
Pernicious Anemia and Hashimotos

23. What is the pathogenesis of IgG AIHA ABO hemolytic disease of a newborn? describe what happens.
A j chain
Paracortex
neutrophilia!
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

24. How is the antigen loaded onto a MHC II?
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
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L
Yes
IgE

25. What lymph node drains the scrotum?
Histamine (causes vasodilation) - leukotrienes (causes bronchoconstriction) - chemotaxins for eos - and heparin (increased blood flow needs to be anticoagulated!)
IL 15; IL 12 - interferon Beta and interferon alpha
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock
Superficial inguinal

26. What is the toxicity of azathioprine?
Internal iliac
T cell precursor
...
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated

27. What are the autoantibodies for systemic sclerosis?
Anti topoisomerase
IL 3; supports growth and differentiation of bone marrow stem cells
Wiskott Aldrich syndrome
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

28. which cells have more complete tolerance - B or T cells?
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
Stimulate the liver to release acute phase reactants
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated
T

29. ________ regulate the cell mediated response.
Humoral
Antimicrosomal and antithyroglobulin
Anemias (esp due to renal failure)
RNA segment reassortment

30. What is the difference of IgE AIHA and IgG AIHA if they are both complement dependent type II hypersensitivities?
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
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
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
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens

31. what else does interferon gamma do other than inducing ribonuclease production - activating NK cells - inducing increased MHC expression?
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
Antibody mediated cytotoxicity; either complement dependent or complement independent
Activate macrophages
All MHC 1/CD8

32. What are HEV? Where are they found? Where does the vasculature of the lymph node travel to?
Superior mesenteric
Hereditary angioedema; PNH
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
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear

33. What links the adaptive and innate immunity?
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs
Complement activation (active in both)
Interferon gamma; Th1
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies

34. What are the autoantibodies for type I diabetes mellitus?
T cells react to the angtigen and activate leukocyted (macrophage acitivation)
opsonizes
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated
Anti glutamate carboxylase and anti insulin

35. What lymph node drains the testes?
Para aortic
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages
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
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels

36. In order to produce Antibodies - does the antigen have to be phagocytosed? give an example with a bug and an autoimmune (type II hypersensitivity for example).
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
Sinusitis - otitis media - pneumonia
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
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!

37. What does granzyme do? who secretes it?
Superficial inguinal
Steroid responsive nephrotic syndrome
TNF alpha and IL1
Its a serine protease that activates apoptosis; NK and CD8

38. What is chronic mucocutaneous candidiasis d/t?
DAF and C1 esterase inhibitor on cells prevent complement activation on their surfaces (microbial surfaces lack this)
carboxy terminal
T cell dysfunction
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis

39. What are the mediators that mast cells release?
By transcytosis
Active; passive - fast but short half life (3 weeks!)
Histamine (causes vasodilation) - leukotrienes (causes bronchoconstriction) - chemotaxins for eos - and heparin (increased blood flow needs to be anticoagulated!)
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

40. What is an autograft? syngeneic graft? allograft? xenograft? What is an ex of an allograft? xenograft?
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
CRP - C3b - IgM
From self; from identical twin or clone; from nonidentical individual of same species; from different species; fetus; pig valve
type four

41. What does Interferon alpha and beta do? how?
secondary
except hyperacute
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells

42. where are complements produced?
Liver! (they are proteins circulating in the blood)
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2
Yes

43. Which antibodies can be multimeric?
IgM and IgA
pale central germinal centers
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
T cells react to the angtigen and activate leukocyted (macrophage acitivation)

44. Type IV hypersensitivity is i...
Liver! (they are proteins circulating in the blood)
isotype
not Ab mediated
dimer

45. IgG...
opsonizes
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
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
Antimicrobial also secreted by CD8 and NK cells that induces apoptsosis

46. How do endotoxin/LPS of gram negative bacteria stimulate the immune system if they do not have a peptide fragment?
Daclizumab; prevent ACUTE rejection of renal transplant
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
By transcytosis
IgA

47. What is a factor that is a predictor for a bad transplantation?
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs
Superior mesenteric
Chronic granulomatous disease
CD56

48. IgM can fix complement but...
cannot cross placenta
IL 4
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
Immune complex - Arthus reaction and Serum sickness; they are all a result of antibody- antigen complex deposition resulting in complement activation

49. What are C1 - C2 - C3 - C4 important for?
C5a
Viral neutralization of igM and IgG!
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
CD56

50. What cytokines are released by Th1 cells?
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants
Not thymus - BM
Anti U1 RNP (ribonucleoprotein)
Interferon gamma and IL 2