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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. IgM can exist as a _______ also
Complement activation (active in both)
acute phase reactants
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils
pentamer

2. Which diseases are associated with DR5?
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
IgAs in mothers breast milk!
NK cells
Pernicious Anemia and Hashimotos

3. What are the autoantibodies for scleroderma (CREST)? scleroderma diffuse?
CRP - C3b - IgM
Anti Jo -1
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids

4. is IgM an opsonizer?
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
Negative!
Superficial inguinal
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

5. Give three examples of bacteria that use antigenic variation and how.
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis
Anti mitochondrial
Recom IL 11; thrombocytopenia

6. IgG...
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
opsonizes
heavy chains
secondary

7. The MALT/GALT are not...
encapsulated
Fc
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening
Severe pyogenic infections early in life

8. What type of fenestrations are found in the red pulp of the spleen?
IgM and IgA
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
Barrel hoop basement membrane fenestrations
IgE

9. which antibodies prevent antigens from binding mucosal surfaces?
mesenchymal
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
IgA

10. What links the adaptive and innate immunity?
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
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
T cell activation; no with CD 4 or CD 8
Complement activation (active in both)

11. What are howell jolly bodies?
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages
Thrombocytopenia
IgE

12. What are the autoantibodies for pemphigus bulgaris?
Antidesmoglein
MS
encapsulated
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages

13. What cytokines do macrophages release? who else can secrete IL 6? IL 12?
Cross link
Anti viral and anti tumor
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells

14. which of the transplant rejections is antibody mediated? why does it occur?
IL 4 - 5 - 10 - 6
MHC class molecules bind to KIRS or CD94 to prevent killing
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )
Alternative splicing of mRNA

15. IgM can fix complement but...
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells
cannot cross placenta
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
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

16. What is an example of a parasite showing antigenic variation?
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
IgG
Hemochromatosis
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)

17. How do you test for chronic granulomatous disease?
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear
Anti mitochondrial
Negative nitroblue tetrazolium reduction test
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells

18. what bacteria are a splenectomy patient most susceptible to? why?
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
pentamer
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)

19. What amine is the main chemical mediator released by mast cells? Where does it act What does it result in?
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated
Histamine; post capillary venules - vasodilation
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency
IgE; by activating eosinophils

20. What is the defect in hyper IgM syndrome? What are the lab results?
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
Paracortex; viral infection
Anemias (esp due to renal failure)
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E

21. Leukocyte adhesion defect presents with...
Local infection/inflammation; infection of the ln itself; metastasis
C5a
neutrophilia!
Histamine; post capillary venules - vasodilation

22. 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
Coarse Faces - cold (noninflamed d/t inability to attract neutrophils) staph abscesses - retained primary teeth - high igE - dermatologic problems (eczema)
Interferon gamma; Th1
Immune complex - Arthus reaction and Serum sickness; they are all a result of antibody- antigen complex deposition resulting in complement activation

23. What type of side chains are found on Fc region of an antibody?
Increases expression of MHC I and MHC II and also activates NK cells
Popliteal
Carbohydrate
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

24. DTH (delayed type hypersensitivity) is the ________ of a PPD reaction
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
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
pathogenesis
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

25. What is thrombopoietin used for?
Thrombocytopenia
...
Activate macrophages
Influenza; antigenic shift; antigenic drift

26. How does igA cross the epithelium?
Anti IF
T cell dysfunction
By transcytosis
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

27. What are complements in the complement system? What activates them? there seems to be different ones - What are these pathways called?
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
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
Antidesmoglein
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)

28. 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
IL 15; IL 12 - interferon Beta and interferon alpha
lowest concentration
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

29. describe the classic complement pathway.
Immune complex - Arthus reaction and Serum sickness; they are all a result of antibody- antigen complex deposition resulting in complement activation
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
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic

30. What lymph node drains the anal canal (below the pectinate line)?
Anti topoisomerase
secondary
Superficial inguinal
Type II hypersensitivity - complement dependent resulting in phagocytosis of RBCs coated with C3b by fixed macrophages in the spleen; Group O mother has anti A - B - IgG Abs that cross placenta and attach to fetal blood group A or B RBCs

31. What is the antimetabolite precursor of 6 mercaptopurine? What is the result?
...
Fab portion
Histamine (causes vasodilation) - leukotrienes (causes bronchoconstriction) - chemotaxins for eos - and heparin (increased blood flow needs to be anticoagulated!)
Internal iliac

32. What is the clinical use of Muromonab?
Anti TSh receptor
IgE; by activating eosinophils
Immunosuppression after kidney transplantation
Type II hypersensitivity - complement dependent resulting in phagocytosis of RBCs coated with C3b by fixed macrophages in the spleen; Group O mother has anti A - B - IgG Abs that cross placenta and attach to fetal blood group A or B RBCs

33. What is an autograft? syngeneic graft? allograft? xenograft? What is an ex of an allograft? xenograft?
From self; from identical twin or clone; from nonidentical individual of same species; from different species; fetus; pig valve
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
Chronic granulomatous disease
MHC class molecules bind to KIRS or CD94 to prevent killing

34. which antibodies can bind complement?
Para aortic
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
except hyperacute
IgM and IgG

35. What are the two signals required for T cells? what happens after?
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
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
Wiskott Aldrich syndrome

36. what results in symptoms of shock in an acute hemolytic transfusion reaction?
A - B - C; all the D's
T cell activation; no with CD 4 or CD 8
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock
CRP - C3b - IgM

37. 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
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
encapsulated
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

38. Name two endogenous pyrogens
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
IL 1 and IL 6
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic
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

39. What is recomb alpha interferon used for?
Anti topoisomerase
Anti Ach receptor
Chronic granulomatous disease
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata

40. In thymic development - What is the positive selection? negative selections?
IgM and IgG
T
When you select for which MHC it will have; take out the lymphs that self react
Pernicious Anemia and Hashimotos

41. What is the main cytokine that activates eosinophils?
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
IL 5
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein
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

42. What does Interferon alpha and beta do? how?
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
IL 1 and IL 6

43. The pathogenesis of contact dermatitis is ________ hypersensitivity
type four
DM type I
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)

44. Type IV hypersensitivity is i...
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
not Ab mediated
2 heavy chains and two light chains
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)

45. 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
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
IL 4 - 5 - 10 - 6
DM type I

46. which of the IL2 inhibitors produce nephrotoxicity? thrombocytopenia/leukopenia?
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)
Axillary
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
Influenza; antigenic shift; antigenic drift

47. What is the pathology of acute transplant rejection? is it reversible?
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants
Anti viral and anti tumor
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
Axillary

48. For which toxins are preformed antibodies (passive) given?
IgG
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill
Tetanus - Botulinum - HBV - Rabies
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic

49. What are the autoantibodies for graves?
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
Anti TSh receptor
A recomb cytokine of IL 2; RCC and metastatic melanoma
Superficial inguinal

50. To what portion of the Antibody do the complements bind?
Cytokine IL 10 secreted by Th2
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
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
Fc

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USMLE Step 1 Immunology

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