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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 is the difference of IgE AIHA and IgG AIHA if they are both complement dependent type II hypersensitivities?
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
Antihistone
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
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.

2. What is the presentation of hyperIgM syndrome?
Severe pyogenic infections early in life
Lymphocytes
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
neutrophilia!

3. Name 5 ways Antibody diversity is generated?
Wiskott Aldrich syndrome
MHC class molecules bind to KIRS or CD94 to prevent killing
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
...

4. What is the end result of complement activation? what bugs are this important for? through what pathway and why?
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
dimer
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
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

5. What is the toxicity of muromonab?
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis
Opsonize bacteria (for enhanced phagocytosis) - neutralize viruses (igG) - activate complement (igM and igG) - sensitize mast cells (igE)
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction
When you select for which MHC it will have; take out the lymphs that self react

6. What is chronic mucocutaneous candidiasis d/t?
T cell dysfunction
active complement pathway
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
pentamer

7. What are the autoantibodies for pemphigus bulgaris?
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
Antidesmoglein
heavy chains
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp

8. What happens in a secondary follicle?
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
Anti SS- A (anti RO) and Anti SS- B
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
Negative nitroblue tetrazolium reduction test

9. What are the cell surface proteins for Macrophages? which two are for opsonins?
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
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
Antimicrosomal and antithyroglobulin

10. What are the function of B cells?
TNF alpha and IL1
Normal pro B (CD 19 +) - no mature B cells results in decreased total B cell level - and decreased amount of immunoglobulins in each class
Secretory component
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated

11. What is the pathogenesis of chronic transplant rejection? When does it occur? is it reversible?
Rheumatic arthritis
IgA
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 :(
IgM and IgD

12. What is hereditary angioedema? What are the C3 levels?
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
MHC I; from RER with help of the B2 microglobulin
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
Intracellular pathogens (acute and chronic viruses and virally induced cancers)

13. What are the four steps in phagocytosis? What are the four disease that correspond to each step?
Anti glutamate carboxylase and anti insulin
Axillary
Opsonization (Brutons agammaglobulinemia) - adhesion (Leukocyte adhesion defect) - phagocytosis (chediak higashi syndrome) - respiratory burst (chronic granulomatous disease)
MHC I; from RER with help of the B2 microglobulin

14. Monomer in circulation - ___ when secreted
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
dimer
Anti alpha subunit 3 of collagen on type IV bm

15. Give three examples of bacteria that use antigenic variation and how.
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein
No because no peptide fragment!
TGF beta and IL 10

16. IgM can fix complement but...
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)
Th2; Th1
cannot cross placenta
Alternative splicing of mRNA

17. What are the autoantibodies for Celiac disease?
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
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)
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
Severe pyogenic infections early in life

18. what will NK cells do to cells covered in IgG Ab? why?
Kill them because they have CD16 on them that recognize the FcG portion
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance
Receiving preformed Antibodies
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles

19. what characterizes an arthus reaction?
Edema and necrosis in that region
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
Pernicious Anemia and Hashimotos
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

20. What is an example of a parasite showing antigenic variation?
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow

21. Which diseases are associated with DR2?
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
Cytokine IL 10 secreted by Th2
MS - hay fever - SLE - goodpastures
MHC class molecules bind to KIRS or CD94 to prevent killing

22. What is the defect in hyper IgM syndrome? What are the lab results?
carboxy terminal
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E
Coarse Faces - cold (noninflamed d/t inability to attract neutrophils) staph abscesses - retained primary teeth - high igE - dermatologic problems (eczema)
TGF beta and IL 10

23. What is serum sickness? give an example.
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
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)

24. where are complements produced?
Antihistone
Paracortex; viral infection
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after
Liver! (they are proteins circulating in the blood)

25. Often bacteria are associated with being killed by humoral immunity. Name some bugs that require cell mediated immunity because they evade humoral response
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
Its a serine protease that activates apoptosis; NK and CD8
Hereditary angioedema; PNH
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

26. What is the presentation of scid? treatment?
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
Anti topoisomerase
pentamer
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill

27. describe the pathogenesis of delayed type IV hypersensitivity
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy
T cells react to the angtigen and activate leukocyted (macrophage acitivation)
pale central germinal centers
IgG

28. What are the autoantibodies for myasthenia gravis?
Previous transfusion; pregnant woman whose fetus had paternal antigens
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein
Anti Ach receptor
Opsonization (Brutons agammaglobulinemia) - adhesion (Leukocyte adhesion defect) - phagocytosis (chediak higashi syndrome) - respiratory burst (chronic granulomatous disease)

29. If the alternative pathway is constitively active - how come normal cells don't get attacked with MAC?
RNA segment reassortment
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear
Superior mesenteric
DAF and C1 esterase inhibitor on cells prevent complement activation on their surfaces (microbial surfaces lack this)

30. What lymph node drains the thigh?
Superficial inguinal
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
Superior mesenteric
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

31. 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?
Fab portion
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
Antidote for digoxin intoxication
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi

32. describe the classic complement pathway.
MHC I - CD16 - CD56
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
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated
...

33. What are the autoantibodies for autoimmune hepatitis?
Recom IL 11; thrombocytopenia
Anti smooth muscle
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)
Anti Jo -1

34. What lymph node drains the testes?
Anti U1 RNP (ribonucleoprotein)
Para aortic
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow
T cell activation; no with CD 4 or CD 8

35. What is the arthus reaction? What is the difference between arthus and serum sickness? give an example. How do you test for it?
Internal iliac
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
Macrophages - Dendritic cells - B cells
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

36. What is Aldesleukin? What is it used for
Tetanus - Botulinum - HBV - Rabies
Not thymus - BM
A recomb cytokine of IL 2; RCC and metastatic melanoma
Cytokine IL 10 secreted by Th2

37. What is the presentation of common variable immunodef? and What are the labs?
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
Lymphocytes
not Ab mediated
IgM and IgA

38. other than C3a - what other complement acts as an anaphyloxin?
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE
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
C5a
Antidesmoglein

39. Which disease is associated with B8?
Previous transfusion; pregnant woman whose fetus had paternal antigens
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
Graves
Antidesmoglein

40. What lymph node drains the lateral side of the dorsum of the foot?
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic
Complement activation (active in both)
Popliteal
Wiskott Aldrich syndrome

41. What lymph node drains the duodenum - jejunum?
Superior mesenteric
Periarteriolar lymphatic sheath in the white pulp that surround that dead end of the capillaries in the red pulp - contain T cells
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening
Antidote for digoxin intoxication

42. IgG...
TGF beta and IL 10
opsonizes
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated
pathogenesis

43. what cytokine does basophils secrete?
Negative!
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
IL 4
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

44. DTH (delayed type hypersensitivity) is the ________ of a PPD reaction
Its a serine protease that activates apoptosis; NK and CD8
Lack of MHC class I constant region which it binds or a nonspecific activation signal (TLR)
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
pathogenesis

45. What are HEV? Where are they found? Where does the vasculature of the lymph node travel to?
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
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
encapsulated
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

46. How does the alternative pathway lead to MAC activation?
CRP - C3b - IgM
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
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
Chronic granulomatous disease

47. What are the three types of lymphocytes?
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )
Superficial inguinal
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
B - T - and NK cells

48. 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
Cyclosporine - OKT3
Superficial inguinal
Stimulate the liver to release acute phase reactants

49. Give an example of someone who could get hyperacute transplant rejection.
Previous transfusion; pregnant woman whose fetus had paternal antigens
S. aureus - E. Coli - aspergillus
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection
Fab portion

50. What is the defect in Leukocyte adhesion defect? What is the presentation? What are the labs?
Complement activation (active in both)
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening
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
Anemias (esp due to renal failure)