Test your basic knowledge |

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. What is the presentation of scid? treatment?
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
Celiac
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
Activates cytotoxic CD 8 T cells as second signal

2. What is the common variable immunodeficiency ? How is it different from Brutons?
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency
Bind FcG for antibody dependent cellular cytotoxicity
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
T cell precursor

3. What are the T cell functions?
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection
IgG
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction

4. What are the main cell surface proteins on B cells?
Anti IF
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
Cyclosporine - OKT3
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7

5. Describe complement dependent Type II hypersensitivity. Give an example.
IL 4 - 5 - 10 - 6
Histamine; post capillary venules - vasodilation
Receiving preformed Antibodies
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

6. What is anergy? why does this occur?
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance
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
Cross link
active complement pathway

7. What cytokines are released by Th1 cells?
Interferon gamma and IL 2
Carbohydrate
Anti IF
Increases expression of MHC I and MHC II and also activates NK cells

8. What is the thymus ? Where is it located? is it encapsulated? How many lobes does it have?
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells
Macrophages - Dendritic cells - B cells
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2
Humoral

9. What are the main Cell surface proteins on T cells?
TGF beta and IL 10
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L
...
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

10. What is a type I hypersensitivity reaction? What is atopic?
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
Anti TSh receptor
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor

11. IgE has the ___________ in the serum
lowest concentration
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!
Recom IL 11; thrombocytopenia
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants

12. What are MHC Class molecules (ie what macromolecule are they made out of)? what gene are responsible for MHC?
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E
False! B cell class switching requires a second signal
Glycoproteins; HLA
IgAs in mothers breast milk!

13. What is the main function of interferons?
No because no peptide fragment!
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E

14. For which toxins are preformed antibodies (passive) given?
Tetanus - Botulinum - HBV - Rabies
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency

15. What are the autoantibodies for drug induced lupus?
...
T cell activation; no with CD 4 or CD 8
Antihistone
Opsonization (Brutons agammaglobulinemia) - adhesion (Leukocyte adhesion defect) - phagocytosis (chediak higashi syndrome) - respiratory burst (chronic granulomatous disease)

16. What does IL 5 do?
delayed!
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils
RNA segment reassortment
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA

17. The lymphocytes are ________ origin
IgM and IgD
mesenchymal
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii
Wiskott Aldrich syndrome

18. Other than stimulating fever - what else does IL 6 do?
IgG
Stimulate the liver to release acute phase reactants
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
T cell precursor

19. can igG cross the placenta?
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
Yes
carboxy terminal
Receiving preformed Antibodies

20. What are complements in the complement system? What activates them? there seems to be different ones - What are these pathways called?
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after
IL 15; IL 12 - interferon Beta and interferon alpha
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)
Proteins; IgG - IgM - endotoxin (microbial surfaces in general - nonspecific ones also) - mannose binding Lectin; classic - alternative - MB pathway (resp)

21. What happens in a deficiency of C3?
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
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
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance

22. What is the main cytokine released by T cells? What does it do
RNA segment reassortment
CD21 on B cells (although there is T cell lymphocytosis in EBV)
IL 3; supports growth and differentiation of bone marrow stem cells
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)

23. What happens in a secondary follicle?
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
Celiac
Immunosuppression after kidney transplantation
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)

24. Monomer in circulation - ___ when secreted
Th2; Th1
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
dimer
IL 3; supports growth and differentiation of bone marrow stem cells

25. what bacteria are a splenectomy patient most susceptible to? why?
Hereditary angioedema; PNH
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
C3b; coating of a pathogen with molecules that promotes phagocytosis; IgG and CRP
IgM

26. What cytokines to Th2 secrete?
Antidote for digoxin intoxication
Type IV
IL 4 - 5 - 10 - 6
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

27. 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?
An anaphylactic immediate reaction; atopy refers to the inherited propensity to develop asthmatic or allergic reactions
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
Axillary
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!

28. What is a factor that is a predictor for a bad transplantation?
Wiskott Aldrich syndrome
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs

29. What are some sinopulmonary infections?
Legionella - N. gonorrhea - L. monocytogenes - viruses - protozoa (leismaniasis)
encapsulated
Sinusitis - otitis media - pneumonia
T cell activation; no with CD 4 or CD 8

30. what ensure that a memory response is generated?
IL 4
In the germinal center of secondary follicles (In the paler center)
If there is class switching and plasma cell production (that is when memory cells are produced)
The igA found in breast milk

31. what happens in a deficiency of C1 esterase inhibitor? DAF?
MHC I; from RER with help of the B2 microglobulin
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
If there is class switching and plasma cell production (that is when memory cells are produced)
Hereditary angioedema; PNH

32. What are the two signals required for B cell class switching? Which is the second signal?
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
A - B - C; all the D's
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
type four

33. What does IgE do on the surface of the mast cell to induce inflammatory mediator release?
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic
Paracortex; viral infection
Cross link
Since it is a comp dependent type II hypersensitivity reaction; C3a brings anaphylotoxins that bring in mediators of shock

34. What are the cell surface proteins on NK cells?
Superior mesenteric
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
MHC I - CD16 - CD56
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)

35. So antibodies are the effectors for the humoral response. List some of their functions.
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
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
Hereditary angioedema; PNH

36. What does granulysin do?
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive
Tetanus - Botulinum - HBV - Rabies
Negative selection
Antimicrobial also secreted by CD8 and NK cells that induces apoptsosis

37. What does CD16 on NK cells do?
Bind FcG for antibody dependent cellular cytotoxicity
heavy chains
Anti alpha subunit 3 of collagen on type IV bm
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)

38. What amine is the main chemical mediator released by mast cells? Where does it act What does it result in?
Increases expression of MHC I and MHC II and also activates NK cells
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill
Histamine; post capillary venules - vasodilation
Th2; Th1

39. What is the clinical use of Muromonab?
Immunosuppression after kidney transplantation
Defect in BTK a tyrosine kinase gene; failed maturation of B cells; X linked recessive
A chemotactic factor for neutrophils
Tetanus - Botulinum - HBV - Rabies

40. Give three examples of bacteria that use antigenic variation and how.
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein
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
lowest concentration
T cell activation; no with CD 4 or CD 8

41. what happens in order for class switching to occur (after being activated by IL and cd40 L)?
T cells react to the angtigen and activate leukocyted (macrophage acitivation)
Recom IL 11; thrombocytopenia
Alternative splicing of mRNA
Monoclonal Ab to CD3- blocks cellular transduction and signaling of T cells

42. What is the marginal zone of the spleen? what happens there?
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
T cell precursor
Hyperacute; presence of preformed antibodies in the recipient ( to blood groups or HLA )
not Ab mediated

43. How is the thymus organized? what happens in each section?
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic
Histamine; post capillary venules - vasodilation
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
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect

44. How does igA cross the epithelium?
Anti viral and anti tumor
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
By transcytosis
Viral neutralization of igM and IgG!

45. Which Thelper cell activated Macrophages? by secreting what? what else does Th1 secrete? For what?
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies

46. How do you test for type III hypersensitivity?
If there is class switching and plasma cell production (that is when memory cells are produced)
Immunoflourescent staining of tissue biopsies
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
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

47. What is the clinical use for sirolimus? what should you combine it with?
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
Basophils! THey want IG E class switch!
IgM

48. What are four results of a splenectomy?
1) susceptibility to encapsulated organisms 2) Howell Jolly Bodies 3) Target cells 4) Thrombocytosis
Digeorge syndrome - 22q11 deletion resulting in failure to develop 3rd and 4th pharyngeal pouches; cardiac and great vessel congenital defects - tetany from hypocalcemia - recurrent viral/fungal infections from T cell deficiency; hypoPTH - hypoCa - a
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
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

49. Which cytokines do Th2 release and For what?
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith

50. What is MHC I made out of? Where is it found? What does it bind to? What type of antigens does it present?
pale central germinal centers
IL 1 and IL 6
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow