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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. 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).
CRP - C3b - IgM
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
Macrophages - Dendritic cells - B cells
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!

2. Which helper T cells' development is induced by IL 4? IL 12?
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
All MHC 1/CD8
Th2; Th1
Type IV

3. What lymph node drains the sigmoid colon?
Inferior mesenteric
Anti mitochondrial
IgE
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

4. A lymph node is a ________ lymphoid organ.
secondary
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
C5a
Complement activation (active in both)

5. What is a type I hypersensitivity reaction? What is atopic?
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
Periarteriolar lymphatic sheath in the white pulp that surround that dead end of the capillaries in the red pulp - contain T cells
IgE; by activating eosinophils

6. can igG cross the placenta?
Yes
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )
Humoral
Paracortex; viral infection

7. Which disease is associated with DR3?
DM type I
MS - hay fever - SLE - goodpastures
MHC I; from RER with help of the B2 microglobulin
opsonizes

8. What is the defect in Leukocyte adhesion defect? What is the presentation? What are the labs?
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
T cell activation; no with CD 4 or CD 8
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)
Severe pyogenic infections early in life

9. explain the process from beginning (ie phagocytosis of the peptide) to end of how Abs are formed in Goodpasteurs.
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
IL 5
IgG
secondary

10. What are target cells?
neutrophilia!
Cells that stil have weird parts of their membrane that macrophages usually bite off
Histamine (causes vasodilation) - leukotrienes (causes bronchoconstriction) - chemotaxins for eos - and heparin (increased blood flow needs to be anticoagulated!)
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency

11. What is colostrum?
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
Acts as second signal on B cells to induce class switching to IgE and IgG
The igA found in breast milk
A recomb cytokine of IL 2; RCC and metastatic melanoma

12. What lymph node drains the stomach?
Anti viral and anti tumor
Celiac
type four
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7

13. Which diseases are associated with DR4?
DM type I and RA
IgG
IL 1 and IL 6
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

14. What are superantigens? give two examples.
Para aortic
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
active complement pathway
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)

15. What is the autoantibody for SLE that is nonspecific? Specific?
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith
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
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive
Lymphocytes

16. which antibody activate mast cells - basophils - and eosinophils?
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak
Graves
IgE
Anti IF

17. What is the general structure of an Ab?
2 heavy chains and two light chains
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
Antimicrosomal and antithyroglobulin
mesenchymal

18. To what portion of the Antibody do the complements bind?
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
Fc
Anti topoisomerase
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies

19. So antibodies are the effectors for the humoral response. List some of their functions.
Hereditary angioedema; PNH
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
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
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)

20. What is the pathogenesis of a candida skin test?
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated
Delayed type hypersensitivity
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7

21. What is the pathology in hyperacute transplant rejection?
Anti viral and anti tumor
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
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
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

22. How do we use thymus dependent antigens to prevent infection from organisms that lack a peptide component?
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
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E
Anti smooth muscle
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants

23. What is immune complex disease? give an example.
acute phase reactants
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
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy

24. which type of immunity is slow but long lasting? as opposed to...
dimer
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
1) VJ light chain random creation 2) VDJ (heavy chain) random creation 3) random combination of light with heavy 4) somatic hypermutation (high frequency mutating that occurs on activation) 5) terminal deoxynucleotidyl transferase (TDT) random additi
Active; passive - fast but short half life (3 weeks!)

25. is IgM an opsonizer?
Its main effect is a defect in Ab opsonization for killing
Celiac
Negative!
Cytokine IL 10 secreted by Th2

26. How is the antigen loaded onto a MHC II?
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
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
cannot cross placenta
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

27. What is the mode of inheritance of Chediak Higashi syndrome? What is the disease d/t? What does it result in? What is the presentation?
Immune complex - Arthus reaction and Serum sickness; they are all a result of antibody- antigen complex deposition resulting in complement activation
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs

28. ________ regulate the cell mediated response.
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE
Humoral
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
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. 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
B - T - and NK cells
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
Alternative splicing of mRNA

30. What amine is the main chemical mediator released by mast cells? Where does it act What does it result in?
T cell dysfunction
T cells react to the angtigen and activate leukocyted (macrophage acitivation)
dimer
Histamine; post capillary venules - vasodilation

31. What is the arthus reaction? What is the difference between arthus and serum sickness? give an example. How do you test for it?
IgE
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
T cell precursor
Anti topoisomerase

32. hat is the presentation of Jobs syndrome or Hyper IgE?
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
MS - hay fever - SLE - goodpastures
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)
Coarse Faces - cold (noninflamed d/t inability to attract neutrophils) staph abscesses - retained primary teeth - high igE - dermatologic problems (eczema)

33. What are the main symptoms of T cell immunodeficiencies?
Recom IL 11; thrombocytopenia
Lymphocytes
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp

34. what prevents NK cells from killing normal cells if their default is to kill?
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock
MHC class molecules bind to KIRS or CD94 to prevent killing
IL 3; supports growth and differentiation of bone marrow stem cells

35. What is the antimetabolite precursor of 6 mercaptopurine? What is the result?
T cells react to the angtigen and activate leukocyted (macrophage acitivation)
...
secondary
Graves

36. Leukocyte adhesion defect presents with...
neutrophilia!
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
except hyperacute
Recom IL 11; thrombocytopenia

37. Which diseases are associated with DR5?
Rheumatic arthritis
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
Pernicious Anemia and Hashimotos
Anti U1 RNP (ribonucleoprotein)

38. what cell surface proteins are on all APCs?
delayed!
Fc
MHC II - B7
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage

39. What do mature naive B lymphocytes express?
IgG
IgM and IgD
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)
Interferon gamma and IL 2

40. Describe the capsular structure of a lymph node; What are the functions of the LN?
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
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
Axillary
Paracortex

41. 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
Anti TSh receptor
Anti glutamate carboxylase and anti insulin
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)

42. To what disease do the autoantibodies to IgG (rheumatoid factor)?
From self; from identical twin or clone; from nonidentical individual of same species; from different species; fetus; pig valve
CRP - C3b - IgM
Rheumatic arthritis
Cells that stil have weird parts of their membrane that macrophages usually bite off

43. How fast does it occur?
Cytokine IL 10 secreted by Th2
The patient could become cyanotic in the OR!
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
NK cells

44. What are some sinopulmonary infections?
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
Sinusitis - otitis media - pneumonia
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!
Acts as second signal on B cells to induce class switching to IgE and IgG

45. What is the thymus ? Where is it located? is it encapsulated? How many lobes does it have?
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2
In the germinal center of secondary follicles (In the paler center)
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
Cytokine IL 10 secreted by Th2

46. __________ are a part of the innate system.
Anti viral and anti tumor
...
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants
NK cells

47. after C3 spontaneously hydrolyzes to C3b and C3a - what happens to C3a?
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
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
IL 3; supports growth and differentiation of bone marrow stem cells
Popliteal

48. Which disease is associated with B8?
Barrel hoop basement membrane fenestrations
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
Superficial inguinal
Graves

49. What cytokines are released by Th1 cells?
Interferon gamma and IL 2
Antihistone
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils

50. What is the defect in Brutons agammaglobulinemia? What is its effect on B cells? What is its inheritance pattern?
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive
TNF alpha and IL1
pathogenesis
Its main effect is a defect in Ab opsonization for killing

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USMLE Step 1 Immunology

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