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USMLE Step 1 Immunology

Subjects : health-sciences, usmle-step-1

Instructions:

Answer 50 questions in 15 minutes.
If you are not ready to take this test, you can study here.
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. What does interferon gamma do to be antiviral?
Increases expression of MHC I and MHC II and also activates NK 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
IgA
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection

2. which of the transplant rejections is antibody mediated? why does it occur?
MHC II - B7
DM type I
delayed!
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )

3. __________ are a part of the innate system.
Sinusitis - otitis media - pneumonia
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
IgG
NK cells

4. What does IL 2 do?
Activates cytotoxic CD 8 T cells as 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
Not thymus - BM
Negative selection

5. Leukocyte adhesion defect presents with...
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
A j chain
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein
neutrophilia!

6. Which is the main antibody that provides passive immunity to infants?
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
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
Complement activation (active in both)
IgG

7. What is digoxin immune Fab used for?
Antidote for digoxin intoxication
MHC I; from RER with help of the B2 microglobulin
Anti smooth muscle
Monoclonal Ab to CD3- blocks cellular transduction and signaling of T cells

8. Name the three opsonins
Recom IL 11; thrombocytopenia
Lymphocytes
Superficial inguinal
CRP - C3b - IgM

9. 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
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith
Sinusitis - otitis media - pneumonia
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE

10. What is the end result of complement activation? what bugs are this important for? through what pathway and why?
MS - hay fever - SLE - goodpastures
IL 15; IL 12 - interferon Beta and interferon alpha
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
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

11. What lymph node drains the duodenum - jejunum?
dimer
IL 4
Histamine; post capillary venules - vasodilation
Superior mesenteric

12. What does CD16 on NK cells do?
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
Both decrease cd8 tcell prolif but one through mtor and the other through calcineurin (resp)
Bind FcG for antibody dependent cellular cytotoxicity
Severe pyogenic infections early in life

13. What is the pathogenesis of acute transplant rejection? When does it occur?
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)
C5a

14. describe the pathogenesis of delayed type IV hypersensitivity
T cells react to the angtigen and activate leukocyted (macrophage acitivation)
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
IgA
Negative nitroblue tetrazolium reduction test

15. after C3 spontaneously hydrolyzes to C3b and C3a - what happens to C3a?
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
Sinusitis - otitis media - pneumonia
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after
Anti IF

16. What is the treatment of acute transplant rejection?
Cyclosporine - OKT3
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
Immunoflourescent staining of tissue biopsies

17. What are some sinopulmonary infections?
Sinusitis - otitis media - pneumonia
Secretory component
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect
Remove encapsulated bacateria

18. IgM can exist as a _______ also
Secretory component
2 heavy chains and two light chains
Induces fever - chemokine secretion to recruit - activates adhesion molecules; macrophages
pentamer

19. What is a type I hypersensitivity reaction? What is atopic?
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
If there is class switching and plasma cell production (that is when memory cells are produced)
Inferior mesenteric
DM type I and RA

20. when can graft versus host disease? What is the result?
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
Viral neutralization of igM and IgG!
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
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

21. in which immunodef order do you see a lot of pus? no pus?
Wiskott Aldrich syndrome
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
Anti glutamate carboxylase and anti insulin
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)

22. What is ataxia telangectasia? What is it caused by? What is the triad of presentation? and its labs?
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
CD56

23. What is the pathogenesis of a hypersensitivity reaction?
Wiskott Aldrich syndrome
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is 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
Not thymus - BM

24. which of the IL2 inhibitors produce nephrotoxicity? thrombocytopenia/leukopenia?
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
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)
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
IgG

25. What are the two signals required for Th1 cells? what happens after then activated?
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
Cytokine IL 10 secreted by Th2
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
Anti TSh receptor

26. What is the main function of TNF alpha? How does it do this?
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak

27. What are the main symptoms of T cell immunodeficiencies?
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
active complement pathway
DAF and C1 esterase inhibitor on cells prevent complement activation on their surfaces (microbial surfaces lack this)
Intracellular pathogens (acute and chronic viruses and virally induced cancers)

28. The alternative pathway is the only constutively...
MHC I - CD16 - CD56
C3b; coating of a pathogen with molecules that promotes phagocytosis; IgG and CRP
active complement pathway
Stimulate the liver to release acute phase reactants

29. where do NK cells develop?
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear
Antimicrobial also secreted by CD8 and NK cells that induces apoptsosis
Not thymus - BM
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi

30. can igG cross the placenta?
DM type I
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
S. aureus - E. Coli - aspergillus
Yes

31. What lymph node drains the upper limb?
IgM
In the germinal center of secondary follicles (In the paler center)
Axillary
Activates Th1 helper cells; Macrophages

32. What do multimeric antibodies require for assembly?
pale central germinal centers
A j chain
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
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage

33. Name three things that IL 1 does as a cytokine. other than the liver - who secretes IL 1
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
Induces fever - chemokine secretion to recruit - activates adhesion molecules; 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
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage

34. which antibodies prevent antigens from binding mucosal surfaces?
IgA
lowest concentration
Internal iliac
encapsulated

35. What is colostrum?
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
The igA found in breast milk
A B and T cell disorder; X linked recessive; progressive deletion of B and T cells; thrombocytopenic purpura - infections - eczema; high IgE and IgA but low IgM

36. 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
Anti Jo -1
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
T cells react to the angtigen and activate leukocyted (macrophage acitivation)

37. Which disease is associated withB B27?
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E
Para aortic
Wiskott Aldrich syndrome

38. What is the result of an IL 12 deficiency? What is the presentation? What are the labs?
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
Activates Th1 helper cells; Macrophages
encapsulated
Superficial inguinal

39. What is the toxicity of azathioprine?
...
cannot cross placenta
Hereditary angioedema; PNH
Negative nitroblue tetrazolium reduction test

40. Often bacteria are associated with being killed by humoral immunity. Name some bugs that require cell mediated immunity because they evade humoral response
Antidesmoglein
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
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
Interferon gamma and IL 2

41. what cell surface proteins are on all APCs?
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)
MHC II - B7
Macrophages - Dendritic cells - B cells
This means that MHC can not recognize it and thus will not be phagocytosed. The humoral response rescues - IgM is the primary response attack. Since there is no class switching (without MHC activation no CD40 L and interleukins to activate!) then the

42. which B and T cell disorder presents with specifically low IgM?
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
Immunosuppression after kidney transplantation
Wiskott Aldrich syndrome
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)

43. The idiotype; the Fc portion determines the...
isotype
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow
carboxy terminal
Previous transfusion; pregnant woman whose fetus had paternal antigens

44. What is Aldesleukin? What is it used for
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect
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
A recomb cytokine of IL 2; RCC and metastatic melanoma
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE

45. What lymph node drains the stomach?
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1
Anti U1 RNP (ribonucleoprotein)
MHC class molecules bind to KIRS or CD94 to prevent killing
Celiac

46. Which is the most abundant antibody in blood?
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)
IgG
IL 15; IL 12 - interferon Beta and interferon alpha
isotype

47. What type of side chains are found on Fc region of an antibody?
Influenza; antigenic shift; antigenic drift
Anemias (esp due to renal failure)
Carbohydrate
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)

48. What are the autoantibodies for pernicious anemia?
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
CD56
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
Anti IF

49. What are the main cell surface proteins on B cells?
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1
Yes
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7

50. What is the autoantibody for SLE that is nonspecific? Specific?
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii
A j chain
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!
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith