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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. IgM can fix complement but...
cannot cross placenta
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
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
Inferior mesenteric

2. What are the three types of Type III hypersensitivity ? What is the common mechanism between them?
Immune complex - Arthus reaction and Serum sickness; they are all a result of antibody- antigen complex deposition resulting in complement activation
CD56
T cell precursor
IL 3; supports growth and differentiation of bone marrow stem cells

3. Describe the capsular structure of a lymph node; What are the functions of the LN?
MHC I/CD8 and IL2/IL 2 Receptor (IL 2 is from Th1!); cytoxicity!
T cell activation; no with CD 4 or CD 8
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
Glycoproteins; HLA

4. other than C3a - what other complement acts as an anaphyloxin?
isotype
C5a
IgE
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

5. Which are the only two antiinflammatory cytokines?
Delayed type hypersensitivity
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
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated
TGF beta and IL 10

6. The alternative pathway is the only constutively...
active complement pathway
Alternative splicing of mRNA
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)
Immunosuppression after kidney transplantation

7. The two heavy chains of an antibody contribute to the...
IgM and IgA
Antihistone
Fab portion
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal

8. What is the presentation of common variable immunodef? and What are the labs?
Anti TSh receptor
Type IV
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
Barrel hoop basement membrane fenestrations

9. What lymph node drains the scrotum?
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction
Superficial inguinal
Lack of MHC class I constant region which it binds or a nonspecific activation signal (TLR)
Anti viral and anti tumor

10. Which is the main antibody that provides passive immunity to infants?
IgG
CRP - C3b - IgM
Remove encapsulated bacateria
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

11. If an antigen lacks a peptide component How does the adaptive immunity attack it? What type of response is this called. give an example of bugs that do this. what implications does this have on splenectomy?
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
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

12. What is the main function of interferons?
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
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
Antiviral for uninfected cells (for future protection) and kills virally infected cells (NK activation)
Increases expression of MHC I and MHC II and also activates NK cells

13. What is the monoclonal antibody to IL2 on activated T cells? What is it used for?
Daclizumab; prevent ACUTE rejection of renal transplant
Axillary
A recomb cytokine of IL 2; RCC and metastatic melanoma
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii

14. What are the main symptoms of T cell immunodeficiencies?
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
IL 4 - 5 - 10 - 6
Anti Ach receptor
Wiskott Aldrich syndrome

15. What lymph node drains the duodenum - jejunum?
T
Superior mesenteric
delayed!
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection

16. How is the thymus organized? what happens in each section?
Basophils! THey want IG E class switch!
IgM and IgG
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
except hyperacute

17. after C3 spontaneously hydrolyzes to C3b and C3a - what happens to C3a?
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance
Superficial inguinal
MHC I; from RER with help of the B2 microglobulin

18. What cytokines are released by Th1 cells?
Interferon gamma and IL 2
Anemias (esp due to renal failure)
not Ab mediated
Anti alpha subunit 3 of collagen on type IV bm

19. What is thrombopoietin used for?
Cells that stil have weird parts of their membrane that macrophages usually bite off
From self; from identical twin or clone; from nonidentical individual of same species; from different species; fetus; pig valve
Thrombocytopenia
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

20. What are the PALS?
Activate macrophages
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
Periarteriolar lymphatic sheath in the white pulp that surround that dead end of the capillaries in the red pulp - contain T cells
TNF alpha and IL1

21. What do macrophages secrete that activate Th1 cells to secrete interferon gamma?
dimer
Antidote for digoxin intoxication
TNF alpha and IL1
DM type I

22. What lymph node drains the breast?
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
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!
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
Axillary

23. What kinds of receptors activate innate immunity?
Daclizumab; prevent ACUTE rejection of renal transplant
TLR ad nuclear receptors
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages
Remove encapsulated bacateria

24. What are the autoantibodies for polymyositis and dermatomyositis?
Mycobacterium Tuberculosis - Mycobacterium Avium Intracellulare; Toxoplasmosis Gondii
pentamer
Daclizumab; prevent ACUTE rejection of renal transplant
Anti Jo -1

25. Which helper T cells' development is induced by IL 4? IL 12?
Th2; Th1
A recomb cytokine of IL 2; RCC and metastatic melanoma
encapsulated
Fab portion

26. What part of the complement system also acts as an opsonin? What is opsonization? can you Name two other opsonins?
pale central germinal centers
Steroid responsive nephrotic syndrome
C3b; coating of a pathogen with molecules that promotes phagocytosis; IgG and CRP
Opsonization (Brutons agammaglobulinemia) - adhesion (Leukocyte adhesion defect) - phagocytosis (chediak higashi syndrome) - respiratory burst (chronic granulomatous disease)

27. Which type of selection of thymic development provides central tolerance?
Fc
Increases expression of MHC I and MHC II and also activates NK cells
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
Negative selection

28. What is a factor that is a predictor for a bad transplantation?
Make antibody - allergy type 1 (igE) - Cytotoxic and immunecomplex hypersensitivity type II and III (igG); hyperacute organ rejection is Ab mediated
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
Basophils! THey want IG E class switch!
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs

29. What is an autograft? syngeneic graft? allograft? xenograft? What is an ex of an allograft? xenograft?
From self; from identical twin or clone; from nonidentical individual of same species; from different species; fetus; pig valve
Fab portion
C - ANCA (antiproteinase); in neutrophil; c= cytoplasmic
Lack of response from lymphocytes when activated; because they are self reactive - this is a form of tolerance

30. The idiotype; the Fc portion determines the...
isotype
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
IL 4
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening

31. What are the two signals required for B cell class switching? Which is the second signal?
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
Celiac
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
B - T - and NK cells

32. DTH (delayed type hypersensitivity) is the ________ of a PPD reaction
pathogenesis
delayed!
IgM
Anti TSh receptor

33. Which Thelper cell activated Macrophages? by secreting what? what else does Th1 secrete? For what?
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
A chemotactic factor for neutrophils
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

34. What cytokines to Th2 secrete?
IL 4 - 5 - 10 - 6
Delayed type hypersensitivity
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata
Celiac

35. What are the main cell surface proteins on B cells?
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils
Daclizumab; prevent ACUTE rejection of renal transplant
HBV - HBC - Kaposis - leukemias - malignant melanoma - hairy cell leukemia and condyluma accuminata

36. What does IgA pick up from epithelial cells before being secreted?
Secretory component
Kill them because they have CD16 on them that recognize the FcG portion
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
The patient could become cyanotic in the OR!

37. What is recomb gamma interferon used for?
Remove encapsulated bacateria
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
Chronic granulomatous disease
Negative nitroblue tetrazolium reduction test

38. What lymph node drains the rectum (above the pectinate line)?
All MHC 1/CD8
Internal iliac
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
Recom IL 11; thrombocytopenia

39. What is the thymus ? Where is it located? is it encapsulated? How many lobes does it have?
Anti Ach receptor
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2
IgAs in mothers breast milk!
Superficial inguinal

40. What is the main function of IL 8?
Activates Th1 helper cells; Macrophages
A chemotactic factor for neutrophils
Anti IF
Adaptive uses classic pathway to kill; innate uses alternative pathway to kill

41. which immunodeficiency presents with delayed separation of the umbilicus? ataxia? telangiectasia?albinism? anaphylaxis on exposure to blood products with IgA? tetany?retained primary teeth? peripheral neuropathy?
Negative nitroblue tetrazolium reduction test
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
Interferon gamma; Th1
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect

42. What are the labs in brutons agammaglobulinemia?
Fab portion
Glycoproteins; HLA
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
Normal pro B (CD 19 +) - no mature B cells results in decreased total B cell level - and decreased amount of immunoglobulins in each class

43. what will NK cells do to cells covered in IgG Ab? why?
Kill them because they have CD16 on them that recognize the FcG portion
Tetanus - Botulinum - HBV - Rabies
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
acute phase reactants

44. What portion of the lymph node is not well developed in DiGeorge Syndrome?
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency
Paracortex
Induces fever - chemokine secretion to recruit - activates adhesion molecules; macrophages
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy

45. which antibodies prevent antigens from binding mucosal surfaces?
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
IgE; by activating eosinophils
IgA
Axillary

46. What does Interferon alpha and beta do? how?
C3b; coating of a pathogen with molecules that promotes phagocytosis; IgG and CRP
IgG
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells
From self; from identical twin or clone; from nonidentical individual of same species; from different species; fetus; pig valve

47. What does IL 4 do?
Acts as second signal on B cells to induce class switching to IgE and IgG
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
IgE; by activating eosinophils
active complement pathway

48. Describe the complement independent Type II hypersenstivity reaction. Give an example.
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization
Anti U1 RNP (ribonucleoprotein)
Increases expression of MHC I and MHC II and also activates NK cells
The antibodies (igM or IgG) either neutralize the target directly (cytoxic!) or recruit leukocytes (Neutrophils and Macrophages!) to incite tissue damage

49. What are the autoantibodies for sjorgens syndrome?
Yes
Opsonization (Brutons agammaglobulinemia) - adhesion (Leukocyte adhesion defect) - phagocytosis (chediak higashi syndrome) - respiratory burst (chronic granulomatous disease)
delayed!
Anti SS- A (anti RO) and Anti SS- B

50. What is the common variable immunodeficiency ? How is it different from Brutons?
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
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
Local infection/inflammation; infection of the ln itself; metastasis
Cytokine release syndrome due to initial release from initial binding (fever etc) and hypersensitivity reaction

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USMLE Step 1 Immunology

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