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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. What are the PALS?
Not thymus - BM
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
Periarteriolar lymphatic sheath in the white pulp that surround that dead end of the capillaries in the red pulp - contain T cells

2. What is the autoantibody for SLE that is nonspecific? Specific?
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith

3. What is serum sickness? give an example.
Edema and necrosis in that region
Not thymus - BM
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock
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

4. What is hereditary angioedema? What are the C3 levels?
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated
Active; passive - fast but short half life (3 weeks!)
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
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

5. What are the T cell functions?
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection
RNA segment reassortment
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
Graves

6. what bacteria are a splenectomy patient most susceptible to? why?
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear
Paracortex
Carbohydrate
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

7. Which is the most abundant antibody in blood?
Edema and necrosis in that region
Complement activation (active in both)
IgG
Negative nitroblue tetrazolium reduction test

8. 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
Influenza; antigenic shift; antigenic drift
Anti Ach receptor
except hyperacute

9. what mediates the type II hypersensitivity? What are the two different methods?
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis
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
Antibody mediated cytotoxicity; either complement dependent or complement independent
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii

10. What does interferon gamma do to be antiviral?
Increases expression of MHC I and MHC II and also activates NK cells
Superficial inguinal
A chemotactic factor for neutrophils
A - B - C; all the D's

11. IgG...
Anti SS- A (anti RO) and Anti SS- B
opsonizes
Interferon gamma; Th1
Anti U1 RNP (ribonucleoprotein)

12. What is the pathogenesis of a candida skin test?
Delayed type hypersensitivity
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)
MS - hay fever - SLE - goodpastures

13. What is the main function of TNF alpha? How does it do this?
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
neutrophilia!
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak
Anti U1 RNP (ribonucleoprotein)

14. Monomer in circulation - ___ when secreted
Cytokine IL 10 secreted by Th2
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
dimer
Superficial inguinal

15. What are the autoantibodies for scleroderma (CREST)? scleroderma diffuse?
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)
Edema and necrosis in that region
Delayed type hypersensitivity
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells

16. what characterizes an arthus reaction?
Histamine; post capillary venules - vasodilation
Edema and necrosis in that region
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency
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

17. What do multimeric antibodies require for assembly?
Axillary
Basophils! THey want IG E class switch!
A j chain
The igA found in breast milk

18. which B and T cell disorder presents with specifically low IgM?
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE
CD21 on B cells (although there is T cell lymphocytosis in EBV)
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
Wiskott Aldrich syndrome

19. The pathogenesis of contact dermatitis is ________ hypersensitivity
type four
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
Antidote for digoxin intoxication
Recom IL 11; thrombocytopenia

20. What are the mediators that mast cells release?
Histamine (causes vasodilation) - leukotrienes (causes bronchoconstriction) - chemotaxins for eos - and heparin (increased blood flow needs to be anticoagulated!)
Yes
False! B cell class switching requires a second signal
secondary

21. Which diseases are associated with DR4?
Anti topoisomerase
DM type I and RA
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
Anti TSh receptor

22. The idiotype; the Fc portion determines the...
isotype
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
Activates Th1 helper cells; Macrophages
Antidesmoglein

23. What is Aldesleukin? What is it used for
RNA segment reassortment
Active; passive - fast but short half life (3 weeks!)
A recomb cytokine of IL 2; RCC and metastatic melanoma
secondary

24. which of the transplant rejections is antibody mediated? why does it occur?
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
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )
Fab portion
Its main effect is a defect in Ab opsonization for killing

25. Which disease is associated withB B27?
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
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
Opsonize bacteria (for enhanced phagocytosis) - neutralize viruses (igG) - activate complement (igM and igG) - sensitize mast cells (igE)
Para aortic

26. What are superantigens? give two examples.
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
Bind FcG for antibody dependent cellular cytotoxicity
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
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA

27. What is the white pulp of the spleen?
NK cells
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
Wiskott Aldrich syndrome
A - B - C; all the D's

28. What are the main symptoms of B cell immunodeficiencies?
SP infections
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
type four
T cells react to the angtigen and activate leukocyted (macrophage acitivation)

29. is IgM an opsonizer?
CD56
Negative!
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!

30. What are the two signals required for Th1 cells? what happens after then activated?
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
Anti topoisomerase
Humoral
Complement activation (active in both)

31. How does igA cross the epithelium?
By transcytosis
pale central germinal centers
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
IgG

32. what cytokine does basophils secrete?
IL 4
Tetanus - Botulinum - HBV - Rabies
Basophils! THey want IG E class switch!
Activates cytotoxic CD 8 T cells as second signal

33. What is the most common selective Ig deficiency? What is the presentation?
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii

34. What is the pathology in hyperacute transplant rejection?
DM type I
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency
active complement pathway

35. What is the general structure of an Ab?
pentamer
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance
2 heavy chains and two light chains
IgE

36. 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?
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
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
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
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.

37. What are the autoantibodies for myasthenia gravis?
Kill them because they have CD16 on them that recognize the FcG portion
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs
Anti Ach receptor
encapsulated

38. How is the antigen loaded onto a MHC II?
Secretory component
Axillary
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
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

39. What does interferon gamma do? What two type of cells does it attack mostly?
Interferon gamma and IL 2
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak
Paracortex
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor

40. What is MHC II made out of? Where is it found? What does it bind to? What type of antigens does it present?
Th cells fail to produce interferon gamma; a lot of IgE
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
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
Its main effect is a defect in Ab opsonization for killing

41. 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).
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!
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
T cell precursor
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

42. can igG cross the placenta?
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
Yes
type four
Liver! (they are proteins circulating in the blood)

43. What is immune complex disease? give an example.
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE
Hemochromatosis
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
MS

44. What is recomb alpha interferon used for?
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill
Recom IL 11; thrombocytopenia
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata

45. The two heavy chains of an antibody contribute to the...
TGF beta and IL 10
CRP - C3b - IgM
Fab portion
Activates cytotoxic CD 8 T cells as second signal

46. What does CD16 on NK cells do?
Bind FcG for antibody dependent cellular cytotoxicity
Severe pyogenic infections early in life
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
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

47. How do we use thymus dependent antigens to prevent infection from organisms that lack a peptide component?
From self; from identical twin or clone; from nonidentical individual of same species; from different species; fetus; pig valve
dimer
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
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

48. which type of immunity is slow but long lasting? as opposed to...
All MHC 1/CD8
Active; passive - fast but short half life (3 weeks!)
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)

49. The Fc region is found on the...
carboxy terminal
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak
DM type I

50. ________ regulate the cell mediated response.
MHC I - CD16 - CD56
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
Humoral
IgM and IgA

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USMLE Step 1 Immunology

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