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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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1. Describe the interstitial tissue of a spleen including the sinuses. What type of cells are found in the four structures (cortex - paracortex - medulla and sinuses)?
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
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
Celiac
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

2. 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?
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy
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
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
Lymphocytes

3. The idiotype; the Fc portion determines the...
IgE
isotype
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
Bind FcG for antibody dependent cellular cytotoxicity

4. The alternative pathway is the only constutively...
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after
active complement pathway
Anti viral and anti tumor
T cell precursor

5. Which Thelper cell activated Macrophages? by secreting what? what else does Th1 secrete? For what?
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
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
Histamine; post capillary venules - vasodilation
Stimulate the liver to release acute phase reactants

6. DTH (delayed type hypersensitivity) is the ________ of a PPD reaction
Anti SS- A (anti RO) and Anti SS- B
pathogenesis
MHC II - B7
Kill them because they have CD16 on them that recognize the FcG portion

7. What are the autoantibodies for systemic sclerosis?
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
Anti SS- A (anti RO) and Anti SS- B
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening
Anti topoisomerase

8. Which are the only two antiinflammatory cytokines?
Paracortex; viral infection
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
TGF beta and IL 10
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP

9. Leukocyte adhesion defect presents with...
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
neutrophilia!
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii
mesenchymal

10. Which HLA's are included in MHC I? MHC II?

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11. To what disease do the autoantibodies to IgG (rheumatoid factor)?
Rheumatic arthritis
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
Cross link
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

12. What are the autoantibodies for other vasculitides?
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
IgG
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear

13. What are the autoantibodies for autoimmune hepatitis?
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear
Acts as second signal on B cells to induce class switching to IgE and IgG
Anti smooth muscle

14. Which disease is associated with HLA A3?
Interferon gamma; Th1
Hemochromatosis
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)

15. What cytokines to Th2 secrete?
Anti Jo -1
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
IL 4 - 5 - 10 - 6
Tetanus - Botulinum - HBV - Rabies

16. What lymph node drains the thigh?
Anti Ach receptor
Anti topoisomerase
C5a
Superficial inguinal

17. What are the autoantibodies for myasthenia gravis?
Anti Ach receptor
IL 5
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 anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions

18. What bugs can actually infect the lymph node itself?
Hemochromatosis
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii
Cross link
Recom IL 11; thrombocytopenia

19. What is the autoantibody for SLE that is nonspecific? Specific?
Para aortic
acute phase reactants
Secretory component
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith

20. What are HEV? Where are they found? Where does the vasculature of the lymph node travel to?
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
Anti SS- A (anti RO) and Anti SS- B
TNF alpha and IL1
Macrophages - Dendritic cells - B cells

21. What is MHC I made out of? Where is it found? What does it bind to? What type of antigens does it present?
C5a
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants
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

22. How is the thymus organized? what happens in each section?
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
Paracortex; viral infection
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
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

23. 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!
CD21 on B cells (although there is T cell lymphocytosis in EBV)
Cells that stil have weird parts of their membrane that macrophages usually bite off
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

24. Only the _______ contribute to the Fc region
From self; from identical twin or clone; from nonidentical individual of same species; from different species; fetus; pig valve
...
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic
heavy chains

25. what happens in order for class switching to occur (after being activated by IL and cd40 L)?
CRP - C3b - IgM
cannot cross placenta
Alternative splicing of mRNA
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!

26. What are C1 - C2 - C3 - C4 important for?
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
acute phase reactants
Viral neutralization of igM and IgG!
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

27. What lymph node drains the upper limb?
S. aureus - E. Coli - aspergillus
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection
Axillary

28. which B and T cell disorder presents with specifically low IgM?
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
Brain - eyes - placenta/fetus - testicles; because they can have an antigen in there and not get attacked by immune system because dont have contact with immune system via blood and lymph; if an infection occurs such that trauma results in exposure t
Wiskott Aldrich syndrome
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

29. What are MHC Class molecules (ie what macromolecule are they made out of)? what gene are responsible for MHC?
mesenchymal
Glycoproteins; HLA
Monoclonal Ab to CD3- blocks cellular transduction and signaling of T cells
Histamine; post capillary venules - vasodilation

30. What lymph node drains the breast?
Axillary
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear
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
delayed!

31. What is wiskott aldrich syndrome? What is its mode of inheritance? What is the pathogenesis of disease? What is its triad of presentation? what labs does it present with?
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated
...
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

32. What is an example of a parasite showing antigenic variation?
Acts as second signal on B cells to induce class switching to IgE and IgG
Receiving preformed Antibodies
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
Lymphocytes

33. What lymph node drains the anal canal (below the pectinate line)?
Superficial inguinal
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
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

34. How does the alternative pathway lead to MAC activation?
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
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells
Normal pro B (CD 19 +) - no mature B cells results in decreased total B cell level - and decreased amount of immunoglobulins in each class
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith

35. Describe complement dependent Type II hypersensitivity. Give an example.
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
mesenchymal
Yes
Immunoflourescent staining of tissue biopsies

36. What are the autoantibodies for sjorgens syndrome?
Anti SS- A (anti RO) and Anti SS- B
Kill them because they have CD16 on them that recognize the FcG portion
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
MS

37. What are the autoantibodies for pemphigus bulgaris?
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages
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
Cross link
Antidesmoglein

38. What is serum sickness? give an example.
MHC I - CD16 - CD56
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
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
Fab portion

39. What is chronic mucocutaneous candidiasis d/t?
Th cells fail to produce interferon gamma; a lot of IgE
Superior mesenteric
T cell dysfunction
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )

40. What lymph node drains the scrotum?
Superficial inguinal
Activates cytotoxic CD 8 T cells as second signal
T cell precursor
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)

41. What are the autoantibodies for hashimotos?
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
Antimicrosomal and antithyroglobulin
Anti SS- A (anti RO) and Anti SS- B
C5a

42. Name 5 ways Antibody diversity is generated?
encapsulated
Viral neutralization of igM and IgG!
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
Lack of MHC class I constant region which it binds or a nonspecific activation signal (TLR)

43. Which diseases are associated with DR4?
DM type I and RA
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
Activate macrophages
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!

44. What lymph node drains the rectum (above the pectinate line)?
Internal iliac
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells

45. when can graft versus host disease? What is the result?
IgM and IgG
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
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
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect

46. What are the autoantibodies for goodpastures syndrome?
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
Carbohydrate
Anti alpha subunit 3 of collagen on type IV bm
Liver! (they are proteins circulating in the blood)

47. What are the four steps in phagocytosis? What are the four disease that correspond to each step?
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs
False! B cell class switching requires a second signal
Opsonization (Brutons agammaglobulinemia) - adhesion (Leukocyte adhesion defect) - phagocytosis (chediak higashi syndrome) - respiratory burst (chronic granulomatous disease)
not Ab mediated

48. The ______ in the BM are DN - the DP are in the cortex of thymus
T cell precursor
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
Histamine; post capillary venules - vasodilation
Negative selection

49. what results in symptoms of shock in an acute hemolytic transfusion reaction?
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill
Anti IF
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock
Type IV

50. What are the autoantibodies for type I diabetes mellitus?
...
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
IL 4
Anti glutamate carboxylase and anti insulin