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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. What does IL 5 do?
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils
...
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
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

2. What are the PALS?
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
IgM and IgG
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
Periarteriolar lymphatic sheath in the white pulp that surround that dead end of the capillaries in the red pulp - contain T cells

3. what happens in a deficiency of C1 esterase inhibitor? DAF?
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
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
Anti Ach receptor
Hereditary angioedema; PNH

4. 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
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
MHC I; from RER with help of the B2 microglobulin
Thrombocytopenia

5. Which is the most abundant antibody in blood?
IgG
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance

6. What is passive immunity?
not Ab mediated
Sinusitis - otitis media - pneumonia
Interferon gamma; Th1
Receiving preformed Antibodies

7. Complements are...
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
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
IgG
acute phase reactants

8. What is the pathogenesis of a hypersensitivity reaction?
lowest concentration
Negative!
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
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

9. which antibodies prevent antigens from binding mucosal surfaces?
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants
IgA
Rheumatic arthritis

10. 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
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
Opsonization (Brutons agammaglobulinemia) - adhesion (Leukocyte adhesion defect) - phagocytosis (chediak higashi syndrome) - respiratory burst (chronic granulomatous disease)
Celiac

11. What is the pathology seen in chronic transplant rejection?
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
Fc
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening

12. What are the autoantibodies for Celiac disease?
Increases expression of MHC I and MHC II and also activates NK cells
MHC I; from RER with help of the B2 microglobulin
Pernicious Anemia and Hashimotos
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)

13. What are the autoantibodies for hashimotos?
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!
Antimicrosomal and antithyroglobulin

14. If the alternative pathway is constitively active - how come normal cells don't get attacked with MAC?
DAF and C1 esterase inhibitor on cells prevent complement activation on their surfaces (microbial surfaces lack this)
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)

15. What are the main Cell surface proteins on T cells?
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L
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
Anti IF
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

16. other than mediating shock - what else does TNF alpha do? who releases it mainly?
Activates Th1 helper cells; Macrophages
Anti smooth muscle
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive
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

17. 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)?
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
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
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

18. explain the process from beginning (ie phagocytosis of the peptide) to end of how Abs are formed in Goodpasteurs.
Superficial inguinal
T
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
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata

19. What lymph node drains the thigh?
Superficial inguinal
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!
...
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

20. What is digoxin immune Fab used for?
CD21 on B cells (although there is T cell lymphocytosis in EBV)
Antidote for digoxin intoxication
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils
Antihistone

21. What is the main function of interferons?
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK 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
Steroid responsive nephrotic syndrome
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

22. What lymph node drains the stomach?
Celiac
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic
IgM
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1

23. T/F B cells do not require a second signal
False! B cell class switching requires a second signal
Cells that stil have weird parts of their membrane that macrophages usually bite off
Lack of MHC class I constant region which it binds or a nonspecific activation signal (TLR)
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal

24. What is the mechanism for sirolimus? what else it known as?
Anti IF
Anti SS- A (anti RO) and Anti SS- B
Cytokine IL 10 secreted by Th2
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

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

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26. Which disease is associated with HLA A3?
Cross link
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
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
Hemochromatosis

27. What lymph node drains the upper limb?
Axillary
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)
Anti U1 RNP (ribonucleoprotein)
Viral neutralization of igM and IgG!

28. can igG cross the placenta?
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
Yes
Antihistone
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)

29. What are the autoantibodies for pernicious anemia?
Previous transfusion; pregnant woman whose fetus had paternal antigens
Inferior mesenteric
Anti IF
Histamine (causes vasodilation) - leukotrienes (causes bronchoconstriction) - chemotaxins for eos - and heparin (increased blood flow needs to be anticoagulated!)

30. What is wiskott aldrich syndrome? What is its mode of inheritance? What is the pathogenesis of disease? What is its triad of presentation? what labs does it present with?
Receiving preformed Antibodies
Th2; Th1
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
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

31. What is muromonab - CD3 (OKT3)
Monoclonal Ab to CD3- blocks cellular transduction and signaling of T cells
Superficial inguinal
Yes
mesenchymal

32. What are four results of a splenectomy?
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii
mesenchymal
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis
NK cells

33. What is the receptor for EBV? On what cells is that located?
IgG
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells
CD21 on B cells (although there is T cell lymphocytosis in EBV)

34. what will NK cells do to cells covered in IgG Ab? why?
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
Kill them because they have CD16 on them that recognize the FcG portion
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies

35. Type Iv hypersensitivity is...
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)
T cell dysfunction
secondary
delayed!

36. What is oprelevkin? and What is it used for?
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
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
Recom IL 11; thrombocytopenia
Interferon gamma and IL 2

37. What is the defect in Brutons agammaglobulinemia? What is its effect on B cells? What is its inheritance pattern?
IL 15; IL 12 - interferon Beta and interferon alpha
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive
Steroid responsive nephrotic syndrome
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

38. which of the hypersensitivity reactions is not Ab mediated?
opsonizes
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7
Type IV
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!

39. What is an autograft? syngeneic graft? allograft? xenograft? What is an ex of an allograft? xenograft?
MS - hay fever - SLE - goodpastures
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E
From self; from identical twin or clone; from nonidentical individual of same species; from different species; fetus; pig valve
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein

40. ________ regulate the cell mediated response.
Cytokine IL 10 secreted by Th2
Humoral
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after
Antimicrosomal and antithyroglobulin

41. Which TCR MHC system is important for viral immunity? neoplastic? donor graft cells?
All MHC 1/CD8
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
acute phase reactants
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow

42. Which antibodies can be multimeric?
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
type four
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock
IgM and IgA

43. Monomer in circulation - ___ when secreted
IgG
dimer
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
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata

44. What lymph node drains the rectum (above the pectinate line)?
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
Internal iliac

45. What are target cells?
IL 4
Anti topoisomerase
carboxy terminal
Cells that stil have weird parts of their membrane that macrophages usually bite off

46. which antibody activate mast cells - basophils - and eosinophils?
A j chain
IgE
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
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)

47. What are the cell surface proteins for Macrophages? which two are for opsonins?
Lack of MHC class I constant region which it binds or a nonspecific activation signal (TLR)
The igA found in breast milk
Anti Ach receptor
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp

48. 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
Increases expression of MHC I and MHC II and also activates NK cells
Receiving preformed Antibodies
By transcytosis

49. What is an example of a parasite showing antigenic variation?
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
Cyclosporine - OKT3
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect

50. What are the sinusoids of the spleen? What is the difference between a spleen and a lymph node?
Coarse Faces - cold (noninflamed d/t inability to attract neutrophils) staph abscesses - retained primary teeth - high igE - dermatologic problems (eczema)
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
The red pulp of the spleen its where the vasculature channels go through and interact with the parenchyma of the spleen (has macrophages) which empty in the sinuses; they are both encapsulated (with trabeculae) secondary lymphoid organs that trap ant
MS - hay fever - SLE - goodpastures