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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 T cell functions?
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
...

2. What amine is the main chemical mediator released by mast cells? Where does it act What does it result in?
Cyclosporine - OKT3
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
Histamine; post capillary venules - vasodilation
Inferior mesenteric

3. Which diseases are associated with DR5?
Pernicious Anemia and Hashimotos
IgM and IgA
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
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated

4. What are the cell surface proteins for Macrophages? which two are for opsonins?
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
TNF alpha and IL1
Rheumatic arthritis
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic

5. can igG cross the placenta?
Interferon gamma and IL 2
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
Yes
active complement pathway

6. What are the main symptoms of T cell immunodeficiencies?
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
Basophils! THey want IG E class switch!
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
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis

7. What are the autoantibodies for hashimotos?
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
Antimicrosomal and antithyroglobulin
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
All MHC 1/CD8

8. IgM can fix complement but...
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)
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
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
cannot cross placenta

9. What does interferon gamma do? What two type of cells does it attack mostly?
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
Interferon gamma; Th1
TLR ad nuclear receptors
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock

10. what cell surface marker is used for NK cells as it is unique to them?
Humoral
C3b; coating of a pathogen with molecules that promotes phagocytosis; IgG and CRP
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive
CD56

11. What are C1 - C2 - C3 - C4 important for?
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow
Viral neutralization of igM and IgG!
Axillary
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak

12. What part of the lymph node specifically expands during a cellular immune response? when would this occur?
Paracortex; viral infection
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
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
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages

13. other than eat and bite RBCs what else do Macrophages of spleen do>
pentamer
MHC II - B7
Histamine (causes vasodilation) - leukotrienes (causes bronchoconstriction) - chemotaxins for eos - and heparin (increased blood flow needs to be anticoagulated!)
Remove encapsulated bacateria

14. What are complements in the complement system? What activates them? there seems to be different ones - What are these pathways called?
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)
Negative nitroblue tetrazolium reduction test
IgG
A j chain

15. with failed maturation of B cells in Brutons agammaglobulinemia - What is its effect on immune pathways and why?
Its main effect is a defect in Ab opsonization for killing
Secretory component
Fab portion
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

16. IgG...
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
pale central germinal centers
opsonizes

17. What is the pathology seen in chronic transplant rejection?
Graves
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening
CD56
In the germinal center of secondary follicles (In the paler center)

18. What are four results of a splenectomy?
T cell activation; no with CD 4 or CD 8
carboxy terminal
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis
Induces fever - chemokine secretion to recruit - activates adhesion molecules; macrophages

19. What does Interferon alpha and beta do? how?
Opsonize bacteria (for enhanced phagocytosis) - neutralize viruses (igG) - activate complement (igM and igG) - sensitize mast cells (igE)
Superficial inguinal
Antibody mediated cytotoxicity; either complement dependent or complement independent
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells

20. What are the autoantibodies for other vasculitides?
Both decrease cd8 tcell prolif but one through mtor and the other through calcineurin (resp)
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
Hemochromatosis
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear

21. describe the classic complement pathway.
Superior mesenteric
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated
Th2; Th1
Rheumatic arthritis

22. what results in symptoms of shock in an acute hemolytic transfusion reaction?
IgG
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles

23. Leukocyte adhesion defect presents with...
If there is class switching and plasma cell production (that is when memory cells are produced)
Celiac
Yes
neutrophilia!

24. Which Thelper cell activated Macrophages? by secreting what? what else does Th1 secrete? For what?
IL 15; IL 12 - interferon Beta and interferon alpha
IL 1 and IL 6
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
Not thymus - BM

25. What is the difference of IgE AIHA and IgG AIHA if they are both complement dependent type II hypersensitivities?
T cell precursor
Inferior mesenteric
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
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

26. What is an example of a parasite showing antigenic variation?
If there is class switching and plasma cell production (that is when memory cells are produced)
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
except hyperacute
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill

27. What is the pathogenesis of acute transplant rejection? When does it occur?
Antihistone
Anti TSh receptor
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after
Alternative splicing of mRNA

28. What are the three types of Type III hypersensitivity ? What is the common mechanism between them?
C3b; coating of a pathogen with molecules that promotes phagocytosis; IgG and CRP
delayed!
Immune complex - Arthus reaction and Serum sickness; they are all a result of antibody- antigen complex deposition resulting in complement activation
T cells react to the angtigen and activate leukocyted (macrophage acitivation)

29. What does IL 2 do?
Activates cytotoxic CD 8 T cells as second signal
encapsulated
except hyperacute
Antidote for digoxin intoxication

30. are Th cells involved in trapping of antigens of endotoxin/LPS?
No because no peptide fragment!
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic
Recom IL 11; thrombocytopenia
Superior mesenteric

31. What is the defect in Brutons agammaglobulinemia? What is its effect on B cells? What is its inheritance pattern?
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive
Secretory component

32. What is the pathology of acute transplant rejection? is it reversible?
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants
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
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
...

33. How does igA cross the epithelium?
Induces fever - chemokine secretion to recruit - activates adhesion molecules; macrophages
T cell dysfunction
Stimulate the liver to release acute phase reactants
By transcytosis

34. How is i Th1 helper cell inhibited?
Normal pro B (CD 19 +) - no mature B cells results in decreased total B cell level - and decreased amount of immunoglobulins in each class
IgM and IgA
Cytokine IL 10 secreted by Th2
acute phase reactants

35. The lymphocytes are ________ origin
...
Acts as second signal on B cells to induce class switching to IgE and IgG
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids
mesenchymal

36. What are the main symptoms of B cell immunodeficiencies?
SP infections
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive
Paracortex; viral infection
False! B cell class switching requires a second signal

37. What is the pathogenesis of IgG AIHA ABO hemolytic disease of a newborn? describe what happens.
except hyperacute
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
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
Superficial inguinal

38. What is the clinical use for sirolimus? what should you combine it with?
Induces fever - chemokine secretion to recruit - activates adhesion molecules; macrophages
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids
pathogenesis

39. what characterizes an arthus reaction?
Increases expression of MHC I and MHC II and also activates NK cells
Negative nitroblue tetrazolium reduction test
Stimulate the liver to release acute phase reactants
Edema and necrosis in that region

40. Which antibodies can be multimeric?
Glycoproteins; HLA
DM type I and RA
IgM and IgA
Popliteal

41. What kinds of receptors activate innate immunity?
Macrophages - Dendritic cells - B cells
Previous transfusion; pregnant woman whose fetus had paternal antigens
Rheumatic arthritis
TLR ad nuclear receptors

42. What do mature naive B lymphocytes express?
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
IgM and IgD
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith
Carbohydrate

43. Name the three opsonins
cannot cross placenta
Steroid responsive nephrotic syndrome
CRP - C3b - IgM
IL 1 and IL 6

44. How is the thymus organized? what happens in each section?
Fab portion
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
C5a
Remove encapsulated bacateria

45. What is the defect in Leukocyte adhesion defect? What is the presentation? What are the labs?
lowest concentration
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
False! B cell class switching requires a second signal
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

46. What lymph node drains the thigh?
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
Superficial inguinal
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow

47. Often bacteria are associated with being killed by humoral immunity. Name some bugs that require cell mediated immunity because they evade humoral response
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
All MHC 1/CD8
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells

48. What is the autoantibody for SLE that is nonspecific? Specific?
Complement activation (active in both)
IgM
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith

49. What are the autoantibodies for graves?
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency
Para aortic
Influenza; antigenic shift; antigenic drift
Anti TSh receptor

50. What lymph node drains the breast?
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1
Axillary
IgM and IgA

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USMLE Step 1 Immunology

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