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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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Match each statement with the correct term.
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1. What is the pathogenesis of IgG AIHA ABO hemolytic disease of a newborn? describe what happens.
2 heavy chains and two light chains
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
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
Humoral

2. The MALT/GALT are not...
opsonizes
Both decrease cd8 tcell prolif but one through mtor and the other through calcineurin (resp)
encapsulated
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA

3. What is the presentation of common variable immunodef? and What are the labs?
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
From self; from identical twin or clone; from nonidentical individual of same species; from different species; fetus; pig valve
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
Th1; interferon gamma; IL 2 for cytotoxic T cell activation

4. What is the general structure of an Ab?
2 heavy chains and two light chains
Hereditary angioedema; PNH
IgM and IgA
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

5. What is the defect in hyper IgM syndrome? What are the lab results?
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
Antihistone
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E
T cell activation; no with CD 4 or CD 8

6. What does interferon gamma do to be antiviral?
Induce differentiation of T cells into Th1 helper cells and activates NK cells also; B cells
The patient could become cyanotic in the OR!
Increases expression of MHC I and MHC II and also activates NK cells
From self; from identical twin or clone; from nonidentical individual of same species; from different species; fetus; pig valve

7. 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?
IgG and IgM bind to pathogens activating C1 convertase and leads to C2 and C4 and then C3 convertase activated
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
IgA
Th1; interferon gamma; IL 2 for cytotoxic T cell activation

8. What is chronic mucocutaneous candidiasis d/t?
Recomb cytokine of GCSF (granulocyte macrophage colony stimulating factor; for recovery of bone marrow
TNF alpha and IL1
A - B - C; all the D's
T cell dysfunction

9. Which disease is associated with DR7?
TNF alpha and IL1
Para aortic
Steroid responsive nephrotic syndrome
Monoclonal Ab to CD3- blocks cellular transduction and signaling of T cells

10. What is digoxin immune Fab used for?
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
Antidote for digoxin intoxication
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
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith

11. Which antibodies can be multimeric?
IgM and IgA
Antidesmoglein
Graves
...

12. Only the _______ contribute to the Fc region
heavy chains
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
except hyperacute
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor

13. The Fc region is found on the...
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
carboxy terminal
When you select for which MHC it will have; take out the lymphs that self react
Superficial inguinal

14. Describe the Mannose Lectin pathway
Some microbial surfaces (only) have mannan binding lectin which activates a protease that cleaves C2 and C4 which combine to make C3. the rest follows the alternative pathway
Scratch test - histamine mediated wheal; radioimmunosorbent assay (detects specific IgEs in serum)
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP

15. What are the autoantibodies for hashimotos?
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)
Antimicrosomal and antithyroglobulin
Immunoflourescent staining of tissue biopsies
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

16. What is the marginal zone of the spleen? what happens there?
Fibrosis of blood vessels and graft tissue from ischemia; obliterative vascular fibrosis with intimal thickening
pathogenesis
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
DAF and C1 esterase inhibitor on cells prevent complement activation on their surfaces (microbial surfaces lack this)

17. What is serum sickness? give an example.
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
Interferon gamma and IL 2
Anti Jo -1
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

18. IgG...
type four
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
opsonizes
CRP - C3b - IgM

19. What are the cell surface proteins for Macrophages? which two are for opsonins?
Rheumatic arthritis
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
Not thymus - BM
AR; defect in MT function results in decreased transport and phagocytosis; recurrent pyogenic infections by staphylococci and streptococci - partial albinism - and peripheral neuropathy

20. What is the clinical use of Muromonab?
Immunosuppression after kidney transplantation
Alternative splicing of mRNA
IL 3; supports growth and differentiation of bone marrow stem cells
opsonizes

21. What is the pathogenesis of HyperIgE syndrome? What are the labs?
Th cells fail to produce interferon gamma; a lot of IgE
Type III hypersensitivity where an internal antigen antibody complexes activate classical complement pathway resulting in C3a neutrophilic chemotaxis and neutrophilic lysosomal death. SLE
Superficial inguinal
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels

22. What is the main function of TNF alpha? How does it do this?
IL 4 - 5 - 10 - 6
IL 15; IL 12 - interferon Beta and interferon alpha
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak
Superior mesenteric

23. What lymph node drains the stomach?
DM type I and RA
Anti IF
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
Celiac

24. What are the three types of lymphocytes?
RNA segment reassortment
Opsonize bacteria (for enhanced phagocytosis) - neutralize viruses (igG) - activate complement (igM and igG) - sensitize mast cells (igE)
...
B - T - and NK cells

25. What is the most common example of passive immunity?
B - T - and NK cells
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells
IgAs in mothers breast milk!
IgG

26. What are the T cell functions?
IgG
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection
Alternative splicing of mRNA
Receiving preformed Antibodies

27. what cytokine does basophils secrete?
Immunosuppression after kidney transplantation in combination with cyclosporine and corticosteroids
Lack of MHC class I constant region which it binds or a nonspecific activation signal (TLR)
In the germinal center of secondary follicles (In the paler center)
IL 4

28. The ______ in the BM are DN - the DP are in the cortex of thymus
Pernicious Anemia and Hashimotos
T cell precursor
delayed!
opsonizes

29. All transplant rejections - _____________ are mediated by Type IV hypersensitivity
CRP - C3b - IgM
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)
except hyperacute
IgE

30. Leukocyte adhesion defect presents with...
neutrophilia!
Antimicrobial also secreted by CD8 and NK cells that induces apoptsosis
opsonizes
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

31. which of the transplant rejections is antibody mediated? why does it occur?
TNF alpha and IL1
Decreased Th1 response; disseminated mycobacterial infections; decreased interferon gamma
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

32. What is the thymus ? Where is it located? is it encapsulated? How many lobes does it have?
Axillary
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2
Its main effect is a defect in Ab opsonization for killing
Patient has had previous exposure to blood products which result in presence of preformed anti HLA cytotoxic Abs

33. when can graft versus host disease? What is the result?
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
IgM and IgA
CD21 on B cells (although there is T cell lymphocytosis in EBV)
Cross link antigens which increases their phagocytability; activate complement for MAC attack; opsonization; neutralization

34. Give three examples of bacteria that use antigenic variation and how.
Previous transfusion; pregnant woman whose fetus had paternal antigens
IL 1 and IL 6
Cells that stil have weird parts of their membrane that macrophages usually bite off
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein

35. give an example of a virus that uses antigenic variation. What does a major variation result in? minor?
Influenza; antigenic shift; antigenic drift
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency
IL 3; supports growth and differentiation of bone marrow stem cells
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

36. What lymph node drains the thigh?
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
Superficial inguinal
Humoral
except hyperacute

37. What is the presentation of hyperIgM syndrome?
Anti viral and anti tumor
Its a serine protease that activates apoptosis; NK and CD8
Antidesmoglein
Severe pyogenic infections early in life

38. What are the symptoms of serum sickness?
Cytokine IL 10 secreted by Th2
A B and T cell disorder; X linked recessive; progressive deletion of B and T cells; thrombocytopenic purpura - infections - eczema; high IgE and IgA but low IgM
lowest concentration
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy

39. Complements are...
dimer
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
Activate B cells - activate Macrophages - kill viruses directly - delayed cell mediated hypersensitivity - acute and chronic rejection
acute phase reactants

40. What is three common causes of severe combined immunodef? What is the result of all three?
Th cells fail to produce interferon gamma; a lot of IgE
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency
Tetanus - Botulinum - HBV - Rabies
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation

41. What is the receptor for EBV? On what cells is that located?
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
CD40 (on b cell) CD40 ligand on Th2 cell; and interleukins (4 -5 -6) from Th2 cell; CD40 is actually the second signal
CD21 on B cells (although there is T cell lymphocytosis in EBV)
Local infection/inflammation; infection of the ln itself; metastasis

42. From where do cytokines come from?
Lymphocytes
Chronic granulomatous disease
Th cells fail to produce interferon gamma; a lot of IgE
False! B cell class switching requires a second signal

43. What is the treatment of acute transplant rejection?
Anti topoisomerase
Receiving preformed Antibodies
Nuclear remnants that are usually taken out of RBC before complete maturation by Macrophages
Cyclosporine - OKT3

44. What is the symptoms involved in graft versus host disease? it What transplant cases does it usually occur? give an example
heavy chains
IL 4 - 5 - 10 - 6
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
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

45. What is the toxicity of azathioprine?
secondary
...
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
DM type I

46. What are the autoantibodies for polymyositis and dermatomyositis?
Superficial inguinal
Suppresses immune response (also specifically Th1 cells) and activates Th2; regulatory T cells
Anti Jo -1
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

47. What is the pathology in hyperacute transplant rejection?
Anti viral and anti tumor
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
IgE; by activating eosinophils
Coarse Faces - cold (noninflamed d/t inability to attract neutrophils) staph abscesses - retained primary teeth - high igE - dermatologic problems (eczema)

48. What happens in a deficiency of C3?
Anti TSh receptor
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
A B and T cell disorder; defect in DNA repair enzymes; ataxia - telangactasia and IgA def; igA def. and increased AFP
Severe recurrent pyogenic sinus and resp tract And increased susceptibility to type III hypersensitivity like SLE

49. 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
Yes
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
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1

50. What is Aldesleukin? What is it used for
A recomb cytokine of IL 2; RCC and metastatic melanoma
...
CD21 on B cells (although there is T cell lymphocytosis in EBV)
Increases expression of MHC I and MHC II and also activates NK cells

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