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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. 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)
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells

2. what happens in a deficiency of C5- C8? why dont you get recurrent pyogenic infections like in C3 def?
Anemias (esp due to renal failure)
Septicemia with neisseria; because at least you have C3 to act like a neutrophilic chemotactic and an acute phase reactant
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)
IgG

3. What does Interferon alpha and beta do? how?
Thrombocytopenia
Axillary
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
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

4. when can graft versus host disease? What is the result?
Histamine; post capillary venules - vasodilation
False! B cell class switching requires a second signal
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
Inferior mesenteric

5. What cytokines are released by Th1 cells?
Interferon gamma and IL 2
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)
Hemochromatosis
pentamer

6. What are the main cell surface proteins on B cells?
Cross link
Lymphocytes
IL 5
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7

7. How is i Th1 helper cell inhibited?
Th cells fail to produce interferon gamma; a lot of IgE
Yes
Paracortex
Cytokine IL 10 secreted by Th2

8. 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
Histamine (causes vasodilation) - leukotrienes (causes bronchoconstriction) - chemotaxins for eos - and heparin (increased blood flow needs to be anticoagulated!)
dimer
...

9. What is the marginal zone of the spleen? what happens there?
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
IL 15; IL 12 - interferon Beta and interferon alpha
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
Receiving preformed Antibodies

10. T/F B cells do not require a second signal
False! B cell class switching requires a second signal
Edema and necrosis in that region
pale central germinal centers
...

11. How do endotoxin/LPS of gram negative bacteria stimulate the immune system if they do not have a peptide fragment?
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants
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
Antibody mediated cytotoxicity; either complement dependent or complement independent
IL 4 - 5 - 10 - 6

12. What two ways do you test for a type 1 hypersensitivity reaction? what will you see?
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
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
Hereditary angioedema; PNH

13. 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)
MHC class molecules bind to KIRS or CD94 to prevent killing
Antidote for digoxin intoxication
Anti topoisomerase

14. What is the clinical use for sirolimus? what should you combine it with?
Type IV
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids
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 :(

15. What are four results of a splenectomy?
...
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)
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis
secondary

16. which antibodies prevent antigens from binding mucosal surfaces?
IgA
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages
Anti Ach receptor
Immune complex - Arthus reaction and Serum sickness; they are all a result of antibody- antigen complex deposition resulting in complement activation

17. What is the presentation of Brutons agammaglobulinemia?
Internal iliac
The igA found in breast milk
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect
Macrophages - Dendritic cells - B cells

18. What are the three types of Type III hypersensitivity ? What is the common mechanism between them?
TNF alpha and IL1
Immune complex - Arthus reaction and Serum sickness; they are all a result of antibody- antigen complex deposition resulting in complement activation
No because no peptide fragment!
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)

19. What type of cells do NK cells attack? with What tools? by necrosis or apoptosis?
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
A j chain
By transcytosis

20. What is the symptoms involved in graft versus host disease? it What transplant cases does it usually occur? give an example
MS - hay fever - SLE - goodpastures
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils
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
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect

21. What is an example of a parasite showing antigenic variation?
IgE; by activating eosinophils
Immunosuppression after kidney transplantation
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)

22. What are the three types of APCs?
Activate macrophages
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
RNA segment reassortment
Macrophages - Dendritic cells - B cells

23. The ______ in the BM are DN - the DP are in the cortex of thymus
Influenza; antigenic shift; antigenic drift
T cell precursor
Anemias (esp due to renal failure)
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation

24. What do multimeric antibodies require for assembly?
A j chain
carboxy terminal
Hemochromatosis
A chemotactic factor for neutrophils

25. Name two endogenous pyrogens
...
Complement activation (active in both)
IL 1 and IL 6
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE

26. Which is the most abundant antibody in blood?
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1
IgG
Wiskott Aldrich syndrome

27. What is the result of an IL 12 deficiency? What is the presentation? What are the labs?
Paracortex
Both decrease cd8 tcell prolif but one through mtor and the other through calcineurin (resp)
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
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

28. What is the main cytokine released by T cells? What does it do
IL 3; supports growth and differentiation of bone marrow stem cells
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated
T cells react to the angtigen and activate leukocyted (macrophage acitivation)
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

29. In order to produce Antibodies - does the antigen have to be phagocytosed? give an example with a bug and an autoimmune (type II hypersensitivity for example).
Hemochromatosis
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
Normal pro B (CD 19 +) - no mature B cells results in decreased total B cell level - and decreased amount of immunoglobulins in each class
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!

30. What is serum sickness? give an example.
Cyclosporine - OKT3
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
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
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E

31. Name the three opsonins
IgE
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening
CRP - C3b - IgM
carboxy terminal

32. can igG cross the placenta?
Carbohydrate
2 heavy chains and two light chains
Yes
Intracellular pathogens (acute and chronic viruses and virally induced cancers)

33. What type of side chains are found on Fc region of an antibody?
MHC I; from RER with help of the B2 microglobulin
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
Carbohydrate
IL 1 and IL 6

34. The MALT/GALT are not...
encapsulated
Wiskott Aldrich syndrome
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive

35. Name three things that IL 1 does as a cytokine. other than the liver - who secretes IL 1
When you select for which MHC it will have; take out the lymphs that self react
If there is class switching and plasma cell production (that is when memory cells are produced)
Antimicrosomal and antithyroglobulin
Induces fever - chemokine secretion to recruit - activates adhesion molecules; macrophages

36. How does igA cross the epithelium?
By transcytosis
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
MHC class molecules bind to KIRS or CD94 to prevent killing
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!

37. The Fc region is found on the...
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after
carboxy terminal
Cells that stil have weird parts of their membrane that macrophages usually bite off
pathogenesis

38. How does the alternative pathway lead to MAC activation?
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
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
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
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

39. which cells have more complete tolerance - B or T cells?
T
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein
Fc
Popliteal

40. which antibodies can bind complement?
MHC I; from RER with help of the B2 microglobulin
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
pathogenesis
IgM and IgG

41. What does granulysin do?
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
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids
Antimicrobial also secreted by CD8 and NK cells that induces apoptsosis
RNA segment reassortment

42. Only the _______ contribute to the Fc region
Barrel hoop basement membrane fenestrations
heavy chains
Graves
Anti viral and anti tumor

43. What lymph node drains the rectum (above the pectinate line)?
IL 5
A chemotactic factor for neutrophils
Internal iliac
Anti SS- A (anti RO) and Anti SS- B

44. What are the main symptoms of B cell immunodeficiencies?
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
Interferon gamma; Th1
SP infections
Antimicrosomal and antithyroglobulin

45. The secondary follicles have __________; primary follicles are dense
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy
pale central germinal centers
IgM

46. Which disease is associated withB B27?
If there is class switching and plasma cell production (that is when memory cells are produced)
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
TNF alpha and IL1
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils

47. What lymph node drains the duodenum - jejunum?
Superior mesenteric
By transcytosis
Anti topoisomerase
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after

48. What lymph node drains the stomach?
Para aortic
Celiac
Stimulate the liver to release acute phase reactants
Cross link

49. What are the autoantibodies for type I diabetes mellitus?
Anti IF
By transcytosis
Opsonization (Brutons agammaglobulinemia) - adhesion (Leukocyte adhesion defect) - phagocytosis (chediak higashi syndrome) - respiratory burst (chronic granulomatous disease)
Anti glutamate carboxylase and anti insulin

50. which antibody is involved in the primary response or immediate response to an antigen?
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
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
A chemotactic factor for neutrophils
IgM