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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. What is the thymus ? Where is it located? is it encapsulated? How many lobes does it have?
IgG
Secretory component
carboxy terminal
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2

2. What is the receptor for EBV? On what cells is that located?
T
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis
CD21 on B cells (although there is T cell lymphocytosis in EBV)
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

3. To what disease do the autoantibodies to IgG (rheumatoid factor)?
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells
DM type I and RA
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
Rheumatic arthritis

4. What are the four steps in phagocytosis? What are the four disease that correspond to each step?
NK cells
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein
Opsonization (Brutons agammaglobulinemia) - adhesion (Leukocyte adhesion defect) - phagocytosis (chediak higashi syndrome) - respiratory burst (chronic granulomatous disease)

5. What does IgA pick up from epithelial cells before being secreted?
Secretory component
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils
Daclizumab; prevent ACUTE rejection of renal transplant

6. What happens when a T helper cell in the paracortical section encounters an antigen? a cytotoxic t cell? a B cell in the cortical section?
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!
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
Previous transfusion; pregnant woman whose fetus had paternal antigens
Periarteriolar lymphatic sheath in the white pulp that surround that dead end of the capillaries in the red pulp - contain T cells

7. What does CD16 on NK cells do?
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
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
Bind FcG for antibody dependent cellular cytotoxicity
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils

8. Which TCR MHC system is important for viral immunity? neoplastic? donor graft cells?
Th2; Th1
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
Negative nitroblue tetrazolium reduction test
All MHC 1/CD8

9. What part of the complement system also acts as an opsonin? What is opsonization? can you Name two other opsonins?
Anti TSh receptor
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
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
C3b; coating of a pathogen with molecules that promotes phagocytosis; IgG and CRP

10. What is the pathogenesis of chronic transplant rejection? When does it occur? is it reversible?
MS
The patient could become cyanotic in the OR!
T cell and antibody mediated vascular damage due to MHC non self being recognized as self by self lymphocytes and resulting in attack of the foreign antigens it presents (all of them); months to years after; no :(
Cytokine IL 10 secreted by Th2

11. What is recomb beta interferon used for?
MHC II - B7
Immunosuppression after kidney transplantation
IL 15; IL 12 - interferon Beta and interferon alpha
MS

12. Which disease is associated withB B27?
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
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
Closed circuit where go directly to veins and open where squeeze out of capillary sinusoids and interact with either PALS or with macrophages in the cords of Billroth (for antigen immune function or for blood cleaning or for both) and squeeze back in

13. other than C3a - what other complement acts as an anaphyloxin?
Antimicrobial also secreted by CD8 and NK cells that induces apoptsosis
Cells that stil have weird parts of their membrane that macrophages usually bite off
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
C5a

14. What is the most common selective Ig deficiency? What is the presentation?
Induces fever - chemokine secretion to recruit - activates adhesion molecules; macrophages
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
Septicemia with neisseria; because at least you have C3 to act like a neutrophilic chemotactic and an acute phase reactant
Intracellular pathogens (acute and chronic viruses and virally induced cancers)

15. which antibodies can bind complement?
IgM and IgG
Immune complex - Arthus reaction and Serum sickness; they are all a result of antibody- antigen complex deposition resulting in complement activation
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
Humoral

16. What amine is the main chemical mediator released by mast cells? Where does it act What does it result in?
IgAs in mothers breast milk!
pathogenesis
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
Histamine; post capillary venules - vasodilation

17. What are the three immune privileged sites? why are they called that? what happens after infection in these areas?
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect
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
...
Increases expression of MHC I and MHC II and also activates NK cells

18. Often bacteria are associated with being killed by humoral immunity. Name some bugs that require cell mediated immunity because they evade humoral response
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
lowest concentration
T cell activation; no with CD 4 or CD 8
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

19. Which type of selection of thymic development provides central tolerance?
Sinusitis - otitis media - pneumonia
Kill them because they have CD16 on them that recognize the FcG portion
Negative selection
CD56

20. How do you test for type III hypersensitivity?
Hemochromatosis
Chronic granulomatous disease
Immunoflourescent staining of tissue biopsies
opsonizes

21. Which helper T cells' development is induced by IL 4? IL 12?
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
A recomb cytokine of IL 2; RCC and metastatic melanoma
Superficial inguinal
Th2; Th1

22. What type of side chains are found on Fc region of an antibody?
Carbohydrate
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
Fab portion
IgG

23. Which Thelper cell activated Macrophages? by secreting what? what else does Th1 secrete? For what?
Paracortex; viral infection
Cyclosporine - OKT3
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
IL 3; supports growth and differentiation of bone marrow stem cells

24. What are the cell surface proteins on NK cells?
Stimulate the liver to release acute phase reactants
A chemotactic factor for neutrophils
Humoral
MHC I - CD16 - CD56

25. What type of fenestrations are found in the red pulp of the spleen?
Th cells fail to produce interferon gamma; a lot of IgE
Barrel hoop basement membrane fenestrations
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages
Anti alpha subunit 3 of collagen on type IV bm

26. which of the transplant rejections is antibody mediated? why does it occur?
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )
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
Humoral
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated

27. What are the two signals to kill for NK cells?
Lack of MHC class I constant region which it binds or a nonspecific activation signal (TLR)
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
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)

28. What is the defect in Leukocyte adhesion defect? What is the presentation? What are the labs?
Antidote for digoxin intoxication
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
Previous transfusion; pregnant woman whose fetus had paternal antigens
Delayed type hypersensitivity

29. 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!
B - T - and NK cells
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
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)

30. Which is the most abundant antibody in blood?
...
delayed!
IgG
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils

31. So antibodies are the effectors for the humoral response. List some of their functions.
encapsulated
MS - hay fever - SLE - goodpastures
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
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization

32. IgM can fix complement but...
Complement activation (active in both)
cannot cross placenta
MS - hay fever - SLE - goodpastures
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii

33. after C3 spontaneously hydrolyzes to C3b and C3a - what happens to C3a?
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L
Cytokine IL 10 secreted by Th2
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
Anti Ach receptor

34. What is the mechanism for sirolimus? what else it known as?
Stimulate the liver to release acute phase reactants
Alternative splicing of mRNA
IgG
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

35. what cell surface proteins are on all APCs?
Its a serine protease that activates apoptosis; NK and CD8
Sinusitis - otitis media - pneumonia
encapsulated
MHC II - B7

36. What are the T cell functions?
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
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection
Interferon gamma and IL 2

37. 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)?
Liver! (they are proteins circulating in the blood)
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
Cytokine IL 10 secreted by Th2
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

38. What lymph node drains the lateral side of the dorsum of the foot?
Superficial inguinal
Superficial inguinal
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
Popliteal

39. Type IV hypersensitivity is i...
TNF alpha and IL1
Viral neutralization of igM and IgG!
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
not Ab mediated

40. when can graft versus host disease? What is the result?
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
...
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
Its main effect is a defect in Ab opsonization for killing

41. What is an example of a parasite showing antigenic variation?
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
Its a serine protease that activates apoptosis; NK and CD8
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect
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

42. What are the three types of lymphocytes?
B - T - and NK cells
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils
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 antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage

43. What lymph node drains the duodenum - jejunum?
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
Superior mesenteric

44. which of the IL2 inhibitors produce nephrotoxicity? thrombocytopenia/leukopenia?
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
T
Both decrease cd8 tcell prolif but one through mtor and the other through calcineurin (resp)
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)

45. What is the main function of interferons?
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
T cells react to the angtigen and activate leukocyted (macrophage acitivation)
active complement pathway

46. What can cause a lymph node enlargement?
T cell and antibody mediated vascular damage due to MHC non self being recognized as self by self lymphocytes and resulting in attack of the foreign antigens it presents (all of them); months to years after; no :(
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
Local infection/inflammation; infection of the ln itself; metastasis
Both decrease cd8 tcell prolif but one through mtor and the other through calcineurin (resp)

47. What are the autoantibodies for scleroderma (CREST)? scleroderma diffuse?
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy
Anticentromere; anti Scl -70 (anti DNA topoisomerase I)
Septicemia with neisseria; because at least you have C3 to act like a neutrophilic chemotactic and an acute phase reactant
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor

48. The secondary follicles have __________; primary follicles are dense
pale central germinal centers
2 heavy chains and two light chains
T cells react to the angtigen and activate leukocyted (macrophage acitivation)
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear

49. What happens in a deficiency of C3?
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill
Anti glutamate carboxylase and anti insulin
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE

50. Which disease is associated with HLA A3?
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
Hemochromatosis
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
Viral neutralization of igM and IgG!