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USMLE Step 1 Immunology

Subjects : health-sciences, usmle-step-1

Instructions:

Answer 50 questions in 15 minutes.
If you are not ready to take this test, you can study here.
Match each statement with the correct term.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

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. How do endotoxin/LPS of gram negative bacteria stimulate the immune system if they do not have a peptide fragment?
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
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1
Secretory component
Activates cytotoxic CD 8 T cells as second signal

2. The Fc region is found on the...
Superficial inguinal
IL 4
carboxy terminal
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction

3. How is i Th1 helper cell inhibited?
Septicemia with neisseria; because at least you have C3 to act like a neutrophilic chemotactic and an acute phase reactant
Cytokine IL 10 secreted by Th2
type four
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

4. To what disease do the autoantibodies to IgG (rheumatoid factor)?
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
Rheumatic arthritis
Popliteal
pale central germinal centers

5. which cytokine inhibits TH2 cells? secreted by who?
Interferon gamma; Th1
By transcytosis
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
MHC I - CD16 - CD56

6. what results in symptoms of shock in an acute hemolytic transfusion reaction?
...
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
Paracortex
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock

7. what else does interferon gamma do other than inducing ribonuclease production - activating NK cells - inducing increased MHC expression?
MHC I - CD16 - CD56
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
Paracortex
Activate macrophages

8. What does it mean if there are igM in the serum at birth?
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E
Kill them because they have CD16 on them that recognize the FcG portion
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill

9. To what portion of the Antibody do the complements bind?
Activates Th1 helper cells; Macrophages
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
Fc
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation

10. What is filgrastim and sargramostim? and What is it used for?
Macrophages - Dendritic cells - B cells
Type IV
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy

11. What is the white pulp of the spleen?
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
Surrounds the red pulp and begins with PALS and then turns into follicles with B cells/follicles
Paracortex

12. Which antibody mediates immunity to worms? how?
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
RNA segment reassortment
IgE; by activating eosinophils
Negative!

13. What is the pathogenesis of chronic granulomatous disease; What is the presentation? What is the labs?
opsonizes
Increases expression of MHC I and MHC II and also activates NK cells
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)

14. Name 5 ways Antibody diversity is generated?
Anti Jo -1
Barrel hoop basement membrane fenestrations
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
Axillary

15. What is an example of a parasite showing antigenic variation?
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
IgG

16. What are the autoantibodies for autoimmune hepatitis?
T cells react to the angtigen and activate leukocyted (macrophage acitivation)
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
Anti smooth muscle
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels

17. What is the pathogenesis of acute transplant rejection? When does it occur?
Inferior mesenteric
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells
Th cells fail to produce interferon gamma; a lot of IgE
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after

18. Give an example of someone who could get hyperacute transplant rejection.
Previous transfusion; pregnant woman whose fetus had paternal antigens
Daclizumab; prevent ACUTE rejection of renal transplant
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)
A chemotactic factor for neutrophils

19. are Th cells involved in trapping of antigens of endotoxin/LPS?
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
Severe pyogenic infections early in life
No because no peptide fragment!
Anti IF

20. what characterizes an arthus reaction?
Type IV
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
Wiskott Aldrich syndrome
Edema and necrosis in that region

21. What are the main cell surface proteins on B cells?
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7
Axillary
Cross link
Carbohydrate

22. Which type of selection of thymic development provides central tolerance?
Remove encapsulated bacateria
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
Negative selection
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

23. which antibody activate mast cells - basophils - and eosinophils?
T
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated
Negative!
IgE

24. which interleukin receptor is required for NK development? activation?
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
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
IL 15; IL 12 - interferon Beta and interferon alpha
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE

25. What is the main cytokine released by T cells? What does it do
Glycoproteins; HLA
TNF alpha and IL1
IL 3; supports growth and differentiation of bone marrow stem cells
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids

26. What is the pathogenesis of a hypersensitivity reaction?
Bind FcG for antibody dependent cellular cytotoxicity
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
mesenchymal
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)

27. What are the cell surface proteins for Macrophages? which two are for opsonins?
acute phase reactants
neutrophilia!
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
CRP - C3b - IgM

28. Which disease is associated with DR7?
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
Steroid responsive nephrotic syndrome
Recom IL 11; thrombocytopenia
Paracortex

29. which cells have more complete tolerance - B or T cells?
T
MHC class molecules bind to KIRS or CD94 to prevent killing
Remove encapsulated bacateria
Anti U1 RNP (ribonucleoprotein)

30. What is the monoclonal antibody to IL2 on activated T cells? What is it used for?
Daclizumab; prevent ACUTE rejection of renal transplant
Remove encapsulated bacateria
opsonizes
Liver! (they are proteins circulating in the blood)

31. which of the IL2 inhibitors produce nephrotoxicity? thrombocytopenia/leukopenia?
A chemotactic factor for neutrophils
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
TLR ad nuclear receptors
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)

32. IgM can fix complement but...
cannot cross placenta
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
Negative nitroblue tetrazolium reduction test
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

33. What cytokines are released by Th1 cells?
Receiving preformed Antibodies
Interferon gamma and IL 2
The patient could become cyanotic in the OR!
lowest concentration

34. What are the autoantibodies for systemic sclerosis?
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
Antihistone
Anti topoisomerase
MHC II - B7

35. Which Thelper cell activated Macrophages? by secreting what? what else does Th1 secrete? For what?
When you select for which MHC it will have; take out the lymphs that self react
DM type I
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
Negative!

36. What is the clinical use of Muromonab?
Immunosuppression after kidney transplantation
opsonizes
Monoclonal Ab to CD3- blocks cellular transduction and signaling of T cells
Fc

37. What are howell jolly bodies?
Rheumatic arthritis
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages
Anti Jo -1
Activates Th1 helper cells; Macrophages

38. __________ are a part of the innate system.
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
Glycoproteins; HLA
NK cells
Graves

39. What is the pathogenesis of chronic transplant rejection? When does it occur? is it reversible?
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 :(
Anti smooth muscle
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection
delayed!

40. where are complements produced?
By transcytosis
Opsonization (Brutons agammaglobulinemia) - adhesion (Leukocyte adhesion defect) - phagocytosis (chediak higashi syndrome) - respiratory burst (chronic granulomatous disease)
Liver! (they are proteins circulating in the blood)
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

41. give an example of a virus that uses antigenic variation. What does a major variation result in? minor?
IgE; by activating eosinophils
By transcytosis
Cyclosporine and tacrolimus; sirolimus (as well as hyperlipidemia)
Influenza; antigenic shift; antigenic drift

42. Often bacteria are associated with being killed by humoral immunity. Name some bugs that require cell mediated immunity because they evade humoral response
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
IL 5
Thrombocytopenia

43. What does IL 5 do?
DAF and C1 esterase inhibitor on cells prevent complement activation on their surfaces (microbial surfaces lack this)
Anti glutamate carboxylase and anti insulin
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
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils

44. What is the common variable immunodeficiency ? How is it different from Brutons?
Fc
IL 1 and IL 6
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
Negative nitroblue tetrazolium reduction test

45. The ______ in the BM are DN - the DP are in the cortex of thymus
Anemias (esp due to renal failure)
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7
CD21 on B cells (although there is T cell lymphocytosis in EBV)
T cell precursor

46. Which disease is associated with HLA A3?
type four
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
Previous transfusion; pregnant woman whose fetus had paternal antigens
Hemochromatosis

47. What is recomb alpha interferon used for?
Inferior mesenteric
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
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata
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 :(

48. What is the presentation of hyperIgM syndrome?
Severe pyogenic infections early in life
Edema and necrosis in that region
IL 5
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal

49. What lymph node drains the thigh?
Superficial inguinal
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage
Delayed type hypersensitivity

50. Describe the capsular structure of a lymph node; What are the functions of the LN?
Receiving preformed Antibodies
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
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
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1