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USMLE Year 1 > Immunology > Flashcards

Immunology Flashcards

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USMLE® Step 1 flashcards
1
Q

What does an increase in serum myeloperoxidase indicate?

A

Myeloperoxidase is found predominantly in PMNs, can increase following inflammation and infection

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2
Q

Anaphylaxis is a result of ____ degranulation, which can be marked by elevated ____

A

Anaphylaxis = result of widespread basophil and mast cell degranulation, which causes the release of preformed inflammatory mediators including

  • Histamine
  • Tryptase (relatively specific to mast cells)
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3
Q

What is required for mast cell/basophil degranulation?

A

Multiple IgE antibodies become cross-linked –> aggregation of the high-affinity IgE receptor –> activation of non-receptor tyrosine kinases, intracellular cascade –> degranulation

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4
Q

How do IFN alpha and beta help the host to respond to viral infections?

A

IFN A and B help to suppress viral replication by halting protein synthesis and promoting apoptosis of infected cells, thus limiting the ability of viruses to spread through the tissues

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5
Q

What is the mutation in Ataxia-Telangiectasia

A

The ATM gene is mutated, responsible for DNA break repair

Sx of AT: cerebellar ataxia, telangiectasias, predisposed to upper airway infections (IgA deficiency)

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6
Q

B lymphocytes: effective vs intracellular organisms?

A

NO

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7
Q

Which type of immune cells and cytokines work together to wall off TB within a caseous granuloma?

A

CD4+ T helper cells and macrophages

Cytokines = IFN-gamma, IL-12, TNF-alpha

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8
Q

What serologic marker is indicative of HBV infectivity?

A

HBeAg

envelope

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9
Q

Which strep pneumo vaccine (polysaccharide or conjugate) do you give to an infant? Why?

A

Conjugate.

Conjugate vaccines are more strongly immunogenic due to both B and T cell recruitment. The polysaccharide vaccine is poorly immunogenic in infants d/t their relatively immature humoral ab response

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10
Q

What disease is characterized by oculocutaneous albinism, pyogenic infections, and progressive neurologic dysfunction?

A

Chediak-Higashi Syndrome

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11
Q

Congenital heart disease + dysmorphic facies + hypocalcemia

A

DiGeorge’s Syndrome

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12
Q

Severe bacterial and viral infections in infancy + chronic diarrhea + mucocutaneous candidiasis

A

Severe Combined Immune Deficiency (SCID)

lab studies with low-absent CD3+ cells and hypogammaglobulinemia

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13
Q

Recurrent infections that worsen with age + easy bleeding + eczema

A

Wiskott-Aldrich Syndrome

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14
Q

What are the key cells in delayed hypersensitivty (Type IV)

A

Macrophages, CD4 helper cells, CD8 cytotoxic T cells

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15
Q

In what part of the cell is antigen loaded in MHC CI vs MHC CII

A

MHC CI: antigen loaded in RER after delivery via TAP

MCH CII: Antigen loaded following release of invariant chain in an acidified endosome

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16
Q

What receptor activates the extrinsic pathway of apoptosis (key to ridding the body of autoreactive lymphocytes)?

A

Mutations in Fas receptor or Fas Ligand

17
Q

Which cytokines produced by Th2 cells promotes isotype switching to IgE?

A

IL-4 and IL-13

18
Q

What two roles do eosinophils play in the immune system?

A

1) Type I hypersensitivity rxns – synthesize prostaglandins, leukotrienes, and cytokines that contribute to the inflammation seen in the late phase of TI hypersensitivity
2) Parasitic Defense – proliferation and activation via IL 5 from Th2 and mast cells. Eos degranulation releases major basic protein to destroy the antibody-bound parasite (an example of antibody dependent cell-mediated cytotoxicity)

19
Q

What happens in hemolytic disease of the newborn?

A

Fetal erythrocyte opsonization by maternal antibodies

20
Q

Acute transplant rejection occurs via _____

A

sensitization of host T lymphocytes against donor MHC/HLA antigens

21
Q

In a reaction to a transfusion: fever/chills, hypotension, dyspnea, chest/back pain, hemoglobinuria within minutes to hours

A

= Acute hemolytic transfusion reaction

Type II hypersensitivity; d/t ABO mismatch

22
Q

Anaphylaxis during blood transfusions + h/o autoimmune disease/atopy + airway/GI infections

A

Selective IgA deficiency

Most often = asymptomatic

23
Q

Define Negative vs Positive Selection in T cell maturation

A

Negative Selection: elimination of T cells that bind self MHC or self antigens with too much affinity

Positive Selection: T cells that are able to bind self MHC are allowed to survive; T cells must be able to recognize self

24
Q

Recurrent respiratory infections + dextrocardia + infertility

A

Kartagener Syndrome

A form of primary ciliary dyskinesia

25
Q

What type of transplant rejection has “dense interstitial lymphocytic infiltrate”

A

Acute (timeline = weeks to months)

26
Q

What is the cell surface marker for the monocyte/macrophage cell lineage?

A

CD14

27
Q

Who secretes IL-2? What are its effects?

A

IL2 is secreted by T helper cells

  • stimulates growth of CD4 and CD8 T cells
  • stimulates growth of B cells
  • activates NK cells and monocytes
28
Q

Where are T lymphocytes and Dendritic Cells found in the lymph node?

A

Paracortex (between follicles and medulla)

  • this is the area of the LN that becomes enlarged during adaptive cellular immune responses
29
Q

Henoch-Schonlein Purpura is a…

A

IgA immune complex-mediated vasculitis (Type III hypersensitivity)

SX: palpable lower extremity purpura, arthralgias, hematuria, abdominal pain (+/- intasussception) following infection

30
Q

What are the key cytokines that activate Th1 cells?

A

IL 12 and IFN-gamma

31
Q

What causes leukocyte adhesion deficiency?

A

Absence of CD18 antigens necessary for the formation of integrins –> impaired PMN migration and chemotaxis

recurrent bacterial skin and mucosal infections without pus formation (no PMNs at infection sites)

32
Q

What causes Hyper IgM syndrome?

A

(most commonly) due to lack of CD40L on T lymphocytes or genetic deficiency of enzymes responsible for DNA modification necessary for isotype switch.

SX: lymphoid hyperplasia and recurrent sinopulmonary infections

33
Q

Which cytokines secreted by Th2 cells activate eosinophils and promote IgA synthesis?

A

IL-5

34
Q

Secretion of which cytokine from helper T cells recruits bone marrow stem cells?

A

IL-3

35
Q

What is serum sickness?

A

A type III hypersensitivity = vasculitis from tissue deposition of circulating ICs

fever, pruritic skin rash, arthralgias, low serum complement

USMLE Year 1 (6 decks)

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