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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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1. Which antibody mediates immunity to worms? how?
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)
IgE; by activating eosinophils
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
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens

2. What are the autoantibodies for Celiac disease?
IL 4
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)
Previous transfusion; pregnant woman whose fetus had paternal antigens
Its a serine protease that activates apoptosis; NK and CD8

3. What is the end result of complement activation? what bugs are this important for? through what pathway and why?
Glycoproteins; HLA
Bind FcG for antibody dependent cellular cytotoxicity
Inferior mesenteric
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

4. give an example of a virus that uses antigenic variation. What does a major variation result in? minor?
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
Interferon gamma and IL 2
Influenza; antigenic shift; antigenic drift
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)

5. can igG cross the placenta?
MS - hay fever - SLE - goodpastures
Yes
neutrophilia!
Th2; Th1

6. What are the autoantibodies for drug induced lupus?
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
Remove encapsulated bacateria
Antihistone
delayed!

7. What lymph node drains the rectum (above the pectinate line)?
Internal iliac
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
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )

8. which antibodies can bind complement?
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
Wiskott Aldrich syndrome
IgM and IgG
NK cells

9. What does Interferon alpha and beta do? how?
Paracortex; viral infection
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
IgM
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

10. Only the _______ contribute to the Fc region
Cross link
Opsonize bacteria (for enhanced phagocytosis) - neutralize viruses (igG) - activate complement (igM and igG) - sensitize mast cells (igE)
Celiac
heavy chains

11. What are target cells?
Cells that stil have weird parts of their membrane that macrophages usually bite off
DM type I and RA
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill
Anti U1 RNP (ribonucleoprotein)

12. What are the autoantibodies for pernicious anemia?
Anti IF
not Ab mediated
Local infection/inflammation; infection of the ln itself; metastasis
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

13. What are the two signals required for B cell class switching? Which is the second signal?
Superficial inguinal
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!
Antibody mediated cytotoxicity; either complement dependent or complement independent
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal

14. What kinds of receptors activate innate immunity?
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii
IgE
TLR ad nuclear receptors
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

15. What are the cell surface proteins on NK cells?
MS - hay fever - SLE - goodpastures
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
Antihistone
MHC I - CD16 - CD56

16. What is the late phase reaction of anaphylaxis allergy? what mediates it?
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
Th2; Th1
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)
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)

17. what cytokine does basophils secrete?
...
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
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening
IL 4

18. IgM can fix complement but...
cannot cross placenta
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
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!
Tetanus - Botulinum - HBV - Rabies

19. What is the pathogenesis of chronic transplant rejection? When does it occur? is it reversible?
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
Inferior mesenteric
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 :(
Humoral

20. What is the pathology seen in chronic transplant rejection?
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance
B - T - and NK cells
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening

21. Type Iv hypersensitivity is...
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency
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
delayed!
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)

22. To what disease do the autoantibodies to IgG (rheumatoid factor)?
TGF beta and IL 10
Rheumatic arthritis
secondary
IL 15; IL 12 - interferon Beta and interferon alpha

23. Which is the most abundant antibody in blood?
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
Antibody mediated cytotoxicity; either complement dependent or complement independent
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)
IgG

24. What are the main Cell surface proteins on T cells?
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
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
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L
mesenchymal

25. Which are the only two antiinflammatory cytokines?
Opsonization (Brutons agammaglobulinemia) - adhesion (Leukocyte adhesion defect) - phagocytosis (chediak higashi syndrome) - respiratory burst (chronic granulomatous disease)
delayed!
Its a serine protease that activates apoptosis; NK and CD8
TGF beta and IL 10

26. What are the three types of lymphocytes?
Th2; Th1
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )
B - T - and NK cells
Superficial inguinal

27. What is the defect in Brutons agammaglobulinemia? What is its effect on B cells? What is its inheritance pattern?
except hyperacute
CRP - C3b - IgM
Anemias (esp due to renal failure)
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive

28. 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?
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
Severe pyogenic infections early in life
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
Anti viral and anti tumor

29. What is the clinical use for azathioprine?
MS
...
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
IgG

30. IgM can exist as a _______ also
All MHC 1/CD8
isotype
pentamer
Yes

31. What is MHC II made out of? Where is it found? What does it bind to? What type of antigens does it present?
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
Lack of MHC class I constant region which it binds or a nonspecific activation signal (TLR)
MS - hay fever - SLE - goodpastures
...

32. Which is the main antibody in the delayed or secondary response to an antigen?
Steroid responsive nephrotic syndrome
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
IgG
NK cells

33. What are MHC's necessary for? By themselves?
T cell dysfunction
T cell activation; no with CD 4 or CD 8
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
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

34. What are the symptoms of serum sickness?
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
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
A recomb cytokine of IL 2; RCC and metastatic melanoma
NK cells

35. What are the labs in brutons agammaglobulinemia?
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated
Normal pro B (CD 19 +) - no mature B cells results in decreased total B cell level - and decreased amount of immunoglobulins in each class
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )

36. 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?
When you select for which MHC it will have; take out the lymphs that self react
NK cells
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
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi

37. What is colostrum?
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
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 :(
The igA found in breast milk
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

38. IgE has the ___________ in the serum
When you select for which MHC it will have; take out the lymphs that self react
lowest concentration
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation

39. What are the function of B cells?
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated
Complement activation (active in both)
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect

40. What are the autoantibodies for pemphigus bulgaris?
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs
Antibody mediated cytotoxicity; either complement dependent or complement independent
Antidesmoglein
TLR ad nuclear receptors

41. What is the pathogenesis of HyperIgE syndrome? What are the labs?
Th cells fail to produce interferon gamma; a lot of IgE
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata
Antidesmoglein
MS

42. From where do cytokines come from?
Lymphocytes
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
IgM and IgG
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages

43. which of the IL2 inhibitors produce nephrotoxicity? thrombocytopenia/leukopenia?
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7
Anti SS- A (anti RO) and Anti SS- B
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor

44. What are the two signals required for T cells? what happens after?
Periarteriolar lymphatic sheath in the white pulp that surround that dead end of the capillaries in the red pulp - contain T cells
Paracortex
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!
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

45. which antibodies prevent antigens from binding mucosal surfaces?
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
IL 4
IgA

46. when can graft versus host disease? What is the result?
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
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis
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
Para aortic

47. IgG...
opsonizes
Anti mitochondrial
Acts as second signal on B cells to induce class switching to IgE and IgG
T cell activation; no with CD 4 or CD 8

48. What is the thymus ? Where is it located? is it encapsulated? How many lobes does it have?
Celiac
pentamer
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2
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

49. What are some catalase positive organisms?
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
Anti Ach receptor
Anti alpha subunit 3 of collagen on type IV bm
S. aureus - E. Coli - aspergillus

50. What is the cause of thymic aplasia? What is its presentation? What are the labs?
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE
Chronic granulomatous disease
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
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions

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USMLE Step 1 Immunology

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