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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. What amine is the main chemical mediator released by mast cells? Where does it act What does it result in?
Histamine; post capillary venules - vasodilation
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)
MHC class molecules bind to KIRS or CD94 to prevent killing
The patient could become cyanotic in the OR!

2. which cytokine inhibits TH2 cells? secreted by who?
IL 1 and IL 6
IL 4
Defect in B cell maturation; idiopathic - presents at older age and normal number of B cells and hyperplastic germinal centers because B cells can be activated but can not produce Abs
Interferon gamma; Th1

3. What is the most common example of passive immunity?
active complement pathway
dimer
IgAs in mothers breast milk!
All MHC 1/CD8

4. 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
Histamine; post capillary venules - vasodilation
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
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

5. is IgM an opsonizer?
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
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
Induces fever - chemokine secretion to recruit - activates adhesion molecules; macrophages
Negative!

6. What is the pathogenesis of acute transplant rejection? When does it occur?
except hyperacute
IgE; by activating eosinophils
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after
Fc

7. What is a type I hypersensitivity reaction? What is atopic?
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
IgG
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
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

8. where are complements produced?
MS - hay fever - SLE - goodpastures
Influenza; antigenic shift; antigenic drift
cannot cross placenta
Liver! (they are proteins circulating in the blood)

9. What is the thymus ? Where is it located? is it encapsulated? How many lobes does it have?
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2
T cell dysfunction
Anti viral and anti tumor
Graves

10. What cytokines do macrophages release? who else can secrete IL 6? IL 12?
delayed!
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
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
Negative nitroblue tetrazolium reduction test

11. The pathogenesis of contact dermatitis is ________ hypersensitivity
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
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
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
type four

12. What are the autoantibodies for sjorgens syndrome?
Antimicrosomal and antithyroglobulin
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening
Anti SS- A (anti RO) and Anti SS- B

13. What does interferon gamma do to be antiviral?
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance
Defect in B cell maturation; idiopathic - presents at older age and normal number of B cells and hyperplastic germinal centers because B cells can be activated but can not produce Abs
Activate macrophages
Increases expression of MHC I and MHC II and also activates NK cells

14. What is the general structure of an Ab?
Anti topoisomerase
2 heavy chains and two light chains
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
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L

15. How fast does it occur?
IL 4
Liver! (they are proteins circulating in the blood)
Axillary
The patient could become cyanotic in the OR!

16. The idiotype; the Fc portion determines the...
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
type four
isotype
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens

17. What is a factor that is a predictor for a bad transplantation?
Para aortic
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
Immunosuppression after kidney transplantation

18. What are the autoantibodies for drug induced lupus?
Antihistone
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
not Ab mediated
IgE; by activating eosinophils

19. What is MHC II made out of? Where is it found? What does it bind to? What type of antigens does it present?
CRP - C3b - IgM
Monoclonal Ab to CD3- blocks cellular transduction and signaling of T cells
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE

20. What does IL 4 do?
Not thymus - BM
pentamer
Acts as second signal on B cells to induce class switching to IgE and IgG
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)

21. which antibody activate mast cells - basophils - and eosinophils?
Pernicious Anemia and Hashimotos
Paracortex
Anemias (esp due to renal failure)
IgE

22. What is the end result of complement activation? what bugs are this important for? through what pathway and why?
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
Paracortex; viral infection
In the germinal center of secondary follicles (In the paler center)
opsonizes

23. What is the main cytokine released by T cells? What does it do
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
IL 5
IL 3; supports growth and differentiation of bone marrow stem cells
SP infections

24. What are the main Cell surface proteins on T cells?
MS - hay fever - SLE - goodpastures
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L
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
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic

25. Describe the complement independent Type II hypersenstivity reaction. Give an example.
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage
IgG
Activates cytotoxic CD 8 T cells as second signal
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy

26. What are the cell surface proteins on NK cells?
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
Anti mitochondrial
Opsonize bacteria (for enhanced phagocytosis) - neutralize viruses (igG) - activate complement (igM and igG) - sensitize mast cells (igE)
MHC I - CD16 - CD56

27. What do multimeric antibodies require for assembly?
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)
A j chain
MHC I; from RER with help of the B2 microglobulin
TGF beta and IL 10

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

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29. What lymph node drains the lateral side of the dorsum of the foot?
Popliteal
Interferon gamma; Th1
DM type I and RA
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

30. What are the autoantibodies for Celiac disease?
Th cells fail to produce interferon gamma; a lot of IgE
Remove encapsulated bacateria
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)

31. Name the three opsonins
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
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
CRP - C3b - IgM
Activate macrophages

32. What does IL 5 do?
The patient could become cyanotic in the OR!
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
Activates cytotoxic CD 8 T cells as second signal
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils

33. ________ regulate the cell mediated response.
Humoral
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE
Anti smooth muscle
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

34. What are target cells?
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
Cells that stil have weird parts of their membrane that macrophages usually bite off
IgM and IgG
IgG

35. What is the main function of IL 8?
Th2; Th1
CD56
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
A chemotactic factor for neutrophils

36. Which cytokines do Th2 release and For what?
Celiac
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1
Interferon gamma; Th1
Immunosuppression after kidney transplantation

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

38. What is the marginal zone of the spleen? what happens there?
pentamer
When you select for which MHC it will have; take out the lymphs that self react
Not thymus - BM
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

39. Which Thelper cell activated Macrophages? by secreting what? what else does Th1 secrete? For what?
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
type four
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 :(

40. What are C1 - C2 - C3 - C4 important for?
Viral neutralization of igM and IgG!
dimer
Superior mesenteric
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal

41. describe the classic complement pathway.
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated
Immunoflourescent staining of tissue biopsies
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
IgM and IgD

42. What is anergy? why does this occur?
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
The igA found in breast milk
Negative!

43. What are the autoantibodies for polymyositis and dermatomyositis?
Tetanus - Botulinum - HBV - Rabies
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 Jo -1
IgE; by activating eosinophils

44. What is the pathology of acute transplant rejection? is it reversible?
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)
The patient could become cyanotic in the OR!
Its a serine protease that activates apoptosis; NK and CD8
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants

45. which antibodies prevent antigens from binding mucosal surfaces?
IgA
Anti viral and anti tumor
Stimulate the liver to release acute phase reactants
Antihistone

46. what prevents NK cells from killing normal cells if their default is to kill?
Chronic granulomatous disease
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis
MHC class molecules bind to KIRS or CD94 to prevent killing
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

47. which of the IL2 inhibitors produce nephrotoxicity? thrombocytopenia/leukopenia?
Periarteriolar lymphatic sheath in the white pulp that surround that dead end of the capillaries in the red pulp - contain T cells
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)
IL 3; supports growth and differentiation of bone marrow stem cells
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)

48. In thymic development - What is the positive selection? negative selections?
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill
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
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
When you select for which MHC it will have; take out the lymphs that self react

49. Describe the capsular structure of a lymph node; What are the functions of the LN?
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy
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
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
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii

50. What lymph node drains the scrotum?
Superficial inguinal
Immunoflourescent staining of tissue biopsies
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock
Anti glutamate carboxylase and anti insulin