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USMLE Step 1 Immunology

Subjects : health-sciences, usmle-step-1

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Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
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1. How do endotoxin/LPS of gram negative bacteria stimulate the immune system if they do not have a peptide fragment?
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
Antihistone
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
Previous transfusion; pregnant woman whose fetus had paternal antigens

2. What is the result of an IL 12 deficiency? What is the presentation? What are the labs?
2 heavy chains and two light chains
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
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
Recom IL 11; thrombocytopenia

3. Which type of selection of thymic development provides central tolerance?
Negative selection
CD21 on B cells (although there is T cell lymphocytosis in EBV)
Axillary
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak

4. what bacteria are a splenectomy patient most susceptible to? why?
Hemochromatosis
Viral neutralization of igM and IgG!
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
Anti topoisomerase

5. What does IL 5 do?
CD21 on B cells (although there is T cell lymphocytosis in EBV)
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells

6. What is passive immunity?
Receiving preformed Antibodies
Septicemia with neisseria; because at least you have C3 to act like a neutrophilic chemotactic and an acute phase reactant
Basophils! THey want IG E class switch!
except hyperacute

7. What are the sinusoids of the spleen? What is the difference between a spleen and a lymph node?
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
Remove encapsulated bacateria
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
Internal iliac

8. What is ataxia telangectasia? What is it caused by? What is the triad of presentation? and its labs?
active complement pathway
CRP - C3b - IgM
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak

9. What is the mechanism for sirolimus? what else it known as?
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
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
Normal pro B (CD 19 +) - no mature B cells results in decreased total B cell level - and decreased amount of immunoglobulins in each class
Antibody mediated cytotoxicity; either complement dependent or complement independent

10. after C3 spontaneously hydrolyzes to C3b and C3a - what happens to C3a?
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
mesenchymal
Barrel hoop basement membrane fenestrations
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma

11. What are complements in the complement system? What activates them? there seems to be different ones - What are these pathways called?
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)
T cell precursor
Complement activation (active in both)
Septicemia with neisseria; because at least you have C3 to act like a neutrophilic chemotactic and an acute phase reactant

12. The secondary follicles have __________; primary follicles are dense
T
Antimicrobial also secreted by CD8 and NK cells that induces apoptsosis
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
pale central germinal centers

13. Which cytokines do Th2 release and For what?
not Ab mediated
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1
Anti topoisomerase
Barrel hoop basement membrane fenestrations

14. Name three things that IL 1 does as a cytokine. other than the liver - who secretes IL 1
Induces fever - chemokine secretion to recruit - activates adhesion molecules; macrophages
Opsonization (Brutons agammaglobulinemia) - adhesion (Leukocyte adhesion defect) - phagocytosis (chediak higashi syndrome) - respiratory burst (chronic granulomatous disease)
Axillary
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

15. What is an example of a parasite showing antigenic variation?
Recom IL 11; thrombocytopenia
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
Stimulate the liver to release acute phase reactants
...

16. What is the two fates of the RBCs that go through the spleen? what happens eventually to all of them>
encapsulated
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
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE

17. What is colostrum?
Alternative splicing of mRNA
The igA found in breast milk
Basophils! THey want IG E class switch!
Interferon gamma and IL 2

18. What are the autoantibodies for systemic sclerosis?
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
Thrombocytopenia
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
Anti topoisomerase

19. Only the _______ contribute to the Fc region
pentamer
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis
Immunosuppression after kidney transplantation
heavy chains

20. What does granulysin do?
The igA found in breast milk
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
Graves
Antimicrobial also secreted by CD8 and NK cells that induces apoptsosis

21. What is the pathology in hyperacute transplant rejection?
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
TGF beta and IL 10
Its a serine protease that activates apoptosis; NK and CD8
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow

22. explain the process from beginning (ie phagocytosis of the peptide) to end of how Abs are formed in Goodpasteurs.
Axillary
A recomb cytokine of IL 2; RCC and metastatic melanoma
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
Anti glutamate carboxylase and anti insulin

23. What is the pathogenesis of chronic granulomatous disease; What is the presentation? What is the labs?
Monoclonal Ab to CD3- blocks cellular transduction and signaling of T cells
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow
secondary

24. give an example of a virus that uses antigenic variation. What does a major variation result in? minor?
Influenza; antigenic shift; antigenic drift
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
Type IV
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma

25. What is MHC II made out of? Where is it found? What does it bind to? What type of antigens does it present?
Cross link
Acts as second signal on B cells to induce class switching to IgE and IgG
Cells that stil have weird parts of their membrane that macrophages usually bite off
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)

26. 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
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
CRP - C3b - IgM
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

27. which interleukin receptor is required for NK development? activation?
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells
IL 15; IL 12 - interferon Beta and interferon alpha
IgM and IgD
Hemochromatosis

28. DTH (delayed type hypersensitivity) is the ________ of a PPD reaction
Negative!
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
pathogenesis

29. What are howell jolly bodies?
Yes
DM type I and RA
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
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages

30. What lymph node drains the testes?
Para aortic
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
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
Immunosuppression after kidney transplantation

31. What is the symptoms involved in graft versus host disease? it What transplant cases does it usually occur? give an example
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
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
Thrombocytopenia
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

32. What lymph node drains the rectum (above the pectinate line)?
Anti alpha subunit 3 of collagen on type IV bm
IgM and IgD
Internal iliac
SP infections

33. What are the main symptoms of B cell immunodeficiencies?
DM type I and RA
cannot cross placenta
SP infections
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)

34. describe the classic complement pathway.
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
The patient could become cyanotic in the OR!
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated
MHC I - CD16 - CD56

35. What is the pathology seen in chronic transplant rejection?
IL 4
Thrombocytopenia
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening

36. A lymph node is a ________ lymphoid organ.
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
secondary
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)
T

37. What is epo used for?
Complement activation (active in both)
Anemias (esp due to renal failure)
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
TLR ad nuclear receptors

38. give an example of how influenza does a major antigenic shift.
DM type I
Paracortex
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
RNA segment reassortment

39. Which are the only two antiinflammatory cytokines?
TGF beta and IL 10
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage
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
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids

40. What is hereditary angioedema? What are the C3 levels?
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
No because no peptide fragment!
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith
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

41. What is the white pulp of the spleen?
MS - hay fever - SLE - goodpastures
Delayed type hypersensitivity
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy

42. What are MHC's necessary for? By themselves?
T cell activation; no with CD 4 or CD 8
CD21 on B cells (although there is T cell lymphocytosis in EBV)
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
2 heavy chains and two light chains

43. What amine is the main chemical mediator released by mast cells? Where does it act What does it result in?
Active; passive - fast but short half life (3 weeks!)
Para aortic
Hereditary angioedema; PNH
Histamine; post capillary venules - vasodilation

44. Which antibodies can be multimeric?
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)
IgM and IgA
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata

45. where do NK cells develop?
T
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
encapsulated
Not thymus - BM

46. What are the autoantibodies for primary biliary cirrhosis?
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)
Anti mitochondrial
active complement pathway

47. in which immunodef order do you see a lot of pus? no pus?
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
Coarse Faces - cold (noninflamed d/t inability to attract neutrophils) staph abscesses - retained primary teeth - high igE - dermatologic problems (eczema)
Anemias (esp due to renal failure)

48. What is the presentation of hyperIgM syndrome?
Severe pyogenic infections early in life
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
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils
IgM and IgG

49. What lymph node drains the thigh?
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
IL 3; supports growth and differentiation of bone marrow stem cells
Superficial inguinal
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy

50. What is the end result of complement activation? what bugs are this important for? through what pathway and why?
Basophils! THey want IG E class switch!
IL 5
Receiving preformed Antibodies
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

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