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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. where do somatic hypermutation and class switching occur?
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
In the germinal center of secondary follicles (In the paler center)
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )

2. What cytokines do macrophages release? who else can secrete IL 6? IL 12?
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!
IL 4
acute phase reactants

3. What is the pathogenesis of chronic granulomatous disease; What is the presentation? What is the labs?
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
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
Antidesmoglein
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)

4. Name the three opsonins
CRP - C3b - IgM
MS - hay fever - SLE - goodpastures
pentamer
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs

5. What are the autoantibodies for systemic sclerosis?
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
lowest concentration
Anti topoisomerase
Anti mitochondrial

6. What are the sinusoids of the spleen? What is the difference between a spleen and a lymph node?
Daclizumab; prevent ACUTE rejection of renal transplant
Cells that stil have weird parts of their membrane that macrophages usually bite off
Rheumatic arthritis
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

7. which cells have more complete tolerance - B or T cells?
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive
T
Axillary
acute phase reactants

8. What are the autoantibodies for drug induced lupus?
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
...
Antihistone
CRP - C3b - IgM

9. What is colostrum?
The igA found in breast milk
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
Influenza; antigenic shift; antigenic drift
Severe pyogenic infections early in life

10. The Fc region is found on the...
Antidote for digoxin intoxication
carboxy terminal
Hereditary angioedema; PNH
TGF beta and IL 10

11. What are the autoantibodies for pernicious anemia?
Anti IF
type four
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
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels

12. in which immunodef order do you see a lot of pus? no pus?
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
In the germinal center of secondary follicles (In the paler center)
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)

13. IgM can fix complement but...
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
cannot cross placenta
secondary
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

14. Give an example of someone who could get hyperacute transplant rejection.
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
Previous transfusion; pregnant woman whose fetus had paternal antigens
Anti alpha subunit 3 of collagen on type IV bm
Histamine (causes vasodilation) - leukotrienes (causes bronchoconstriction) - chemotaxins for eos - and heparin (increased blood flow needs to be anticoagulated!)

15. What is chronic mucocutaneous candidiasis d/t?
T cell dysfunction
All MHC 1/CD8
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE

16. what mediates the type II hypersensitivity? What are the two different methods?
Antibody mediated cytotoxicity; either complement dependent or complement independent
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
Interferon gamma and IL 2
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

17. What do mature naive B lymphocytes express?
cannot cross placenta
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
Antimicrosomal and antithyroglobulin
IgM and IgD

18. what cell surface proteins are on all APCs?
MHC II - B7
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
Negative nitroblue tetrazolium reduction test
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2

19. What does interferon gamma do to be antiviral?
Lymphocytes
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
Its main effect is a defect in Ab opsonization for killing
Increases expression of MHC I and MHC II and also activates NK cells

20. What is recomb beta interferon used for?
isotype
An antigen encounter (presented by APC for Th2) with Th2 will result in it to go to the cortical section and help with B cell activation; Cytotoxic T cell will enter vasculature/efferent lymph to go kill; B cell will wait for Th2 for activation and t
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic
MS

21. Complements are...
Liver! (they are proteins circulating in the blood)
acute phase reactants
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii
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

22. What is the defect in hyper IgM syndrome? What are the lab results?
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
MS
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma

23. what cytokine does basophils secrete?
MHC I - CD16 - CD56
IL 4
IL 1 and IL 6
Kill them because they have CD16 on them that recognize the FcG portion

24. In thymic development - What is the positive selection? negative selections?
When you select for which MHC it will have; take out the lymphs that self react
Anti viral and anti tumor
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak

25. What is the arthus reaction? What is the difference between arthus and serum sickness? give an example. How do you test for it?
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
isotype
Steroid responsive nephrotic syndrome
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

26. What does CD16 on NK cells do?
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis
Bind FcG for antibody dependent cellular cytotoxicity
IgM
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L

27. What does IgE do on the surface of the mast cell to induce inflammatory mediator release?
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages
Cross link
RNA segment reassortment
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L

28. what bacteria are a splenectomy patient most susceptible to? why?
CRP - C3b - IgM
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages
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
cannot cross placenta

29. What is the mechanism for sirolimus? what else it known as?
Delayed type hypersensitivity
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
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
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

30. what cell surface marker is used for NK cells as it is unique to them?
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)
CD56
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7

31. What are MHC's necessary for? By themselves?
T cell activation; no with CD 4 or CD 8
Cytokine IL 10 secreted by Th2
IgM and IgG
Negative selection

32. What is MHC I made out of? Where is it found? What does it bind to? What type of antigens does it present?
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
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
Anti IF
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein

33. What links the adaptive and innate immunity?
Antibody mediated cytotoxicity; either complement dependent or complement independent
IgM and IgD
Complement activation (active in both)
IgM

34. What type of fenestrations are found in the red pulp of the spleen?
Barrel hoop basement membrane fenestrations
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)
IgG
IL 3; supports growth and differentiation of bone marrow stem cells

35. What is the presentation of Brutons agammaglobulinemia?
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect
Antidesmoglein
CD56
IgG

36. What is the most common example of passive immunity?
type four
IgAs in mothers breast milk!
Antimicrobial also secreted by CD8 and NK cells that induces apoptsosis
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids

37. How do you test for chronic granulomatous disease?
Anti TSh receptor
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance
Negative nitroblue tetrazolium reduction test
Antimicrosomal and antithyroglobulin

38. What is the clinical use for azathioprine?
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
Hemochromatosis
...
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

39. what prevents NK cells from killing normal cells if their default is to kill?
Secretory component
Fab portion
Interferon gamma; Th1
MHC class molecules bind to KIRS or CD94 to prevent killing

40. For which toxins are preformed antibodies (passive) given?
heavy chains
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak
Tetanus - Botulinum - HBV - Rabies

41. What is the toxicity of azathioprine?
...
IgG
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA

42. A lymph node is a ________ lymphoid organ.
secondary
Barrel hoop basement membrane fenestrations
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
CD56

43. What happens in a deficiency of C3?
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
Anti glutamate carboxylase and anti insulin
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
TLR ad nuclear receptors

44. which antibodies prevent antigens from binding mucosal surfaces?
IgA
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
MHC class molecules bind to KIRS or CD94 to prevent killing
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

45. What cytokines to Th2 secrete?
IL 4 - 5 - 10 - 6
Interferon gamma; Th1
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
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive

46. How is the thymus organized? what happens in each section?
TNF alpha and IL1
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
Kill them because they have CD16 on them that recognize the FcG portion
Histamine; post capillary venules - vasodilation

47. What is the main function of IL 8?
Sinusitis - otitis media - pneumonia
IgM and IgG
Remove encapsulated bacateria
A chemotactic factor for neutrophils

48. What is digoxin immune Fab used for?
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
IL 4
Antidote for digoxin intoxication
Anti topoisomerase

49. To what disease do the autoantibodies to IgG (rheumatoid factor)?
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
Rheumatic arthritis
Anti smooth muscle
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

50. Which is the main antibody that provides passive immunity to infants?
IgM and IgD
IL 15; IL 12 - interferon Beta and interferon alpha
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
IgG