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USMLE Step 1 Immunology

Subjects : health-sciences, usmle-step-1

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1. 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
Cytokine IL 10 secreted by Th2
Septicemia with neisseria; because at least you have C3 to act like a neutrophilic chemotactic and an acute phase reactant

2. what prevents NK cells from killing normal cells if their default is to kill?
MHC class molecules bind to KIRS or CD94 to prevent killing
Negative!
DM type I
Cells that stil have weird parts of their membrane that macrophages usually bite off

3. What happens in a secondary follicle?
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
except hyperacute
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!

4. The Fc region is found on the...
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
carboxy terminal
An alpha and beta chain; only on APCs; TCR and CD4; extracellular (phagocytosed by APCs)
Antidote for digoxin intoxication

5. What is the pathogenesis of chronic granulomatous disease; What is the presentation? What is the labs?
Opsonization (Brutons agammaglobulinemia) - adhesion (Leukocyte adhesion defect) - phagocytosis (chediak higashi syndrome) - respiratory burst (chronic granulomatous disease)
Superficial inguinal
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)
From self; from identical twin or clone; from nonidentical individual of same species; from different species; fetus; pig valve

6. 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
T cell activation; no with CD 4 or CD 8
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)
Lack of NADPH oxidase results in a lack of respiratory burst in neutrophils; susceptibility to catalase positive organisms (S. aureus - E. Coli - Aspergillus)

7. Name two endogenous pyrogens
A recomb cytokine of IL 2; RCC and metastatic melanoma
IL 1 and IL 6
All MHC 1/CD8
No because no peptide fragment!

8. What cytokines do macrophages release? who else can secrete IL 6? IL 12?
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
heavy chains
Mediates septic shock; activates the endothelium for adhesion and dilation and leukocyte recruitment results in vascular leak

9. What is the presentation of Brutons agammaglobulinemia?
Recurrent sinopulmonary bacterial infections after 6 months (d/t mothers igGs transplacental) due to opsonization defect
A chemotactic factor for neutrophils
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)
A - B - C; all the D's

10. What is the pathogenesis of a hypersensitivity reaction?
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
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
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
Cells that stil have weird parts of their membrane that macrophages usually bite off

11. What is the difference of IgE AIHA and IgG AIHA if they are both complement dependent type II hypersensitivities?
Complement activation (active in both)
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
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
IL 15; IL 12 - interferon Beta and interferon alpha

12. where are complements produced?
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
Kill them because they have CD16 on them that recognize the FcG portion
Liver! (they are proteins circulating in the blood)
pentamer

13. Which antibody mediates immunity to worms? how?
IgE; by activating eosinophils
Stimulate the liver to release acute phase reactants
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
Anti TSh receptor

14. What lymph node drains the scrotum?
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants
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)
Superficial inguinal
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)

15. What does it mean if there are igM in the serum at birth?
MHC I; from RER with help of the B2 microglobulin
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
mesenchymal
Since cant cross placenta most likely means that child was forced early to produce due to an infection (most likely CMV)

16. What are the autoantibodies for goodpastures syndrome?
MHC II/CD4 and B7 (on APC) and CD28 (on Th cell); releases cytokines to kill those extracellular buggers!
Anti alpha subunit 3 of collagen on type IV bm
Th2; Th1
Superficial inguinal

17. __________ are a part of the innate system.
dimer
IL 1 - IL 6 - IL 12 - TNF alpha; IL 6- Th2 cells; IL 12- B cells
except hyperacute
NK cells

18. What is the marginal zone of the spleen? what happens there?
Anti smooth muscle
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
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
type four

19. What is the arthus reaction? What is the difference between arthus and serum sickness? give an example. How do you test for it?
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
Glycoproteins; HLA
Activates Th1 helper cells; Macrophages
Fab portion

20. What are the symptoms of serum sickness?
CGD; Jobs syndrome (defect in Neutrophil chemotactic response)
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
Fever - urticaria - arthralgias - proteinuria - lymphadenopathy
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies

21. Which disease is associated withB B27?
IgM
Psoriasis - Ankylosis Spondylitis - IBD - Reiters; all seronegative spondylopathies
IgAs in mothers breast milk!
Negative!

22. explain the process from beginning (ie phagocytosis of the peptide) to end of how Abs are formed in Goodpasteurs.
Carbohydrate
IL 5
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
Adenosine deaminase deficiency (AR) - defective IL 2 receptor (X linked) - and failure to synthesize MHC II; both humoral and cell mediated deficiency

23. What lymph node drains the sigmoid colon?
Coarse Faces - cold (noninflamed d/t inability to attract neutrophils) staph abscesses - retained primary teeth - high igE - dermatologic problems (eczema)
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
Inferior mesenteric
Anti alpha subunit 3 of collagen on type IV bm

24. Leukocyte adhesion defect presents with...
neutrophilia!
MHC class molecules bind to KIRS or CD94 to prevent killing
IgA
Antibody mediated cytotoxicity; either complement dependent or complement independent

25. If the alternative pathway is constitively active - how come normal cells don't get attacked with MAC?
When you select for which MHC it will have; take out the lymphs that self react
Recurrent infections to every type of antigen; bone marrow transplant (be weary of GVH disease!)
DAF and C1 esterase inhibitor on cells prevent complement activation on their surfaces (microbial surfaces lack this)
IL 3; supports growth and differentiation of bone marrow stem cells

26. What type of cells do NK cells attack? with What tools? by necrosis or apoptosis?
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis
IgE
Anti nuclear Antibodies (ANA); Anti dsDNA - anti Smith
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

27. is IgM an opsonizer?
T cell precursor
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
Negative!
The place of T cell diff and maturation; ant mediastinum above heart; yes; 2

28. What do macrophages secrete that activate Th1 cells to secrete interferon gamma?
TNF alpha and IL1
B - T - and NK cells
Acts as second signal on B cells to induce class switching to IgA; also stimulates eosinophils
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp

29. What lymph node drains the rectum (above the pectinate line)?
Secretory component
Rheumatic arthritis
Internal iliac
Influenza; antigenic shift; antigenic drift

30. What does Interferon alpha and beta do? how?
MHC II - B7 - CD40 and CD14; CD40 and D14 for FcG and C3b resp
CRP - C3b - IgM
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
Antiviral by inducing ribonuclease which degrades only viral mRNA (prevents protein synthesis) and activates NK cells to kill virus infected cells

31. What are the autoantibodies for systemic sclerosis?
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
Anti topoisomerase
secondary
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis

32. In order to produce Antibodies - does the antigen have to be phagocytosed? give an example with a bug and an autoimmune (type II hypersensitivity for example).
carboxy terminal
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!
Lymphocytes
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)

33. For which toxins are preformed antibodies (passive) given?
DM type I and RA
T cells react to the angtigen and activate leukocyted (macrophage acitivation)
Periarteriolar lymphatic sheath in the white pulp that surround that dead end of the capillaries in the red pulp - contain T cells
Tetanus - Botulinum - HBV - Rabies

34. What lymph node drains the duodenum - jejunum?
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
Superior mesenteric
DM type I and RA
Active; passive - fast but short half life (3 weeks!)

35. What is the pathology of acute transplant rejection? is it reversible?
Recom IL 11; thrombocytopenia
dimer
...
Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate; yes! with immunosuppressants

36. Which cytokines do Th2 release and For what?
Tumor cells and virally infected cells; perforin pore to secrete granzymes through it; apoptosis
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)
Fab portion
IL 4 -5 -6 for B cell class switching - IL 10 to inhibit TH1

37. What are the autoantibodies for Celiac disease?
Antigliadin - antiendomysial (both are IgAs - anti tissue transgluataminase igA)
MS - hay fever - SLE - goodpastures
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after
Its main effect is a defect in Ab opsonization for killing

38. What are the main symptoms of T cell immunodeficiencies?
Lymphocytes
Salmonella - 2 flagellar variants; Borrelia (relapsing fever); and Neisseria gonorrhoaea - pilus protein
Intracellular pathogens (acute and chronic viruses and virally induced cancers)
Antihistone

39. What links the adaptive and innate immunity?
Defect in CD40L results in inability to class switch; a lot of IgM and no IgG - A - E
The igA found in breast milk
Complement activation (active in both)
Ig - CD19 - CD20 - CD21 - CD40 - MHC II - B7

40. after C3 spontaneously hydrolyzes to C3b and C3a - what happens to C3a?
Its involved in inflammation and results in anaphylaxis and neutrophil chemotaxis.
Th1; interferon gamma; IL 2 for cytotoxic T cell activation
C3b; coating of a pathogen with molecules that promotes phagocytosis; IgG and CRP
Antidesmoglein

41. Which antibodies can be multimeric?
Opsonize bacteria (for enhanced phagocytosis) - neutralize viruses (igG) - activate complement (igM and igG) - sensitize mast cells (igE)
Cell mediated due to T cell cytotoxicity reacting to foreign MHCs; few weeks after
Superficial inguinal
IgM and IgA

42. What is the treatment of acute transplant rejection?
Ischemia and necrosis of graft due to occlusion of vessels and fibrinoid necrosis and thrombosis within the vessels
carboxy terminal
Cyclosporine - OKT3
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)

43. hat is the presentation of Jobs syndrome or Hyper IgE?
Coarse Faces - cold (noninflamed d/t inability to attract neutrophils) staph abscesses - retained primary teeth - high igE - dermatologic problems (eczema)
Pernicious Anemia and Hashimotos
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear
Opsonize bacteria (for enhanced phagocytosis) - neutralize viruses (igG) - activate complement (igM and igG) - sensitize mast cells (igE)

44. What is the end result of complement activation? what bugs are this important for? through what pathway and why?
Daclizumab; prevent ACUTE rejection of renal transplant
Th2; Th1
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
...

45. What are the autoantibodies for other vasculitides?
Leukocyte adhesion defect; ataxia telangietasia; ataxia telangiectasia; chediak higashi syndrome; IgA def; Digeorge syndrome; Jobs; Chediak Higashi
P - ANCA (antimyeloperoxidase); in neutrophil; p= perinuclear
Steroid responsive nephrotic syndrome
Anti viral and anti tumor

46. what characterizes an arthus reaction?
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
Edema and necrosis in that region
IgM
TCR - CD4/8 - CD28 (binds B7) - CD3 (for intracellular transduction) - CD40L

47. What is MHC I made out of? Where is it found? What does it bind to? What type of antigens does it present?
MHC I; from RER with help of the B2 microglobulin
A j chain
An alpha chain and a B2 microglobulin; on all nucleated cells; TCR and CD8; intracellular antigens
Anemias (esp due to renal failure)

48. What is hereditary angioedema? What are the C3 levels?
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
IgA; sinus and lung infections from lack of secretory defense - milk allergies and diarrhea from giardiasis; Anaphylasix on exposure to blood products with igA
Normal pro B (CD 19 +) - no mature B cells results in decreased total B cell level - and decreased amount of immunoglobulins in each class
Viral neutralization of igM and IgG!

49. What are the sinusoids of the spleen? What is the difference between a spleen and a lymph node?
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
B - T - and NK cells
When you select for which MHC it will have; take out the lymphs that self react
Axillary

50. What is an example of a parasite showing antigenic variation?
Isotype switching (activated by Th2 cell signals and cytokines) - somatic hypermutation
Trypanosomes with programmed rearrangement (results in recurring fever -- sleeping sickness!)
Activates Macrophages and Th1 cells; suppresses Th2 cells; antiviral and antitumor
Periarteriolar lymphatic sheath in the white pulp that surround that dead end of the capillaries in the red pulp - contain T cells

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USMLE Step 1 Immunology

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