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*USMLE* > Immuno > Flashcards

Immuno Flashcards

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USMLE® Step 1 flashcards
1
Q

DiGeorge syndrome

cause, embryo, sx/signs

A

22q11.2 microdeletion

failure of NC cell migration to THIRD + FOURTH phar. pouch > failed PT and thymic development

HYPOCALCEMIA > tetany, carpopedal spasm, seizure

T cell deficiency > VIRAL/FUNGAL/PROTOZOAL infections

CONOTRUNCAL abn.(interrupted aortic arch / truncus arteriosus)

Chvostek (CN VII tap) and Trousseau (bp cuff) signs + less thymic shadow on CXR

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2
Q

IFN types, where they’re made + effects

A

Type I- alpha/beta; from virus infected cells; paracrine signal to other infected cells > increased RNAse L andprotein kinase R(inhibits eIF-2 + thus translation initiation) in presences ofdsRNA

Type II- gamma; from T/NK cells; stim Th1 diff, incr MHC-II expression, improves intracellular killing by macros

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3
Q

Immune cell receptors which can be blocked by new mAb drugs for cancer therapy

A

PD-1andCTLA-4

stimulation of these receptors lead to T-cell inactivation

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4
Q

What isChediak Higashi syndrome?

triad

A

AR disorder of lysosomal function

triad of…
NEURO ISSUES(nystagmus, periph/cranial neuropathy)
ALBINISM (partial oculocutaneous)
IMMUNODEFICIENCY(defect in neutro phago-lysosome fusion >giant lysosomal inclusionson LM of periph blood + recurrent pyogenic infections by Staph/Strep)

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5
Q

Hematological issues in SLE?

Mechanisms?

A

Can have RBC, PLT and WBC deficits

RBCs - T2 HS rxn with WARM IgG Abs against RBCs causes SPHEROCYTOSIS, positive direct Coombs and extravascular hemolysis

PLTs - same as in ITP (anti-plt Abs)

Leukopenia - Ab-mediate neutrophil destruction (rarer)

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6
Q

Leukocyte Adhesion Deficiency

inheritance? gene? s/s?

A

AR disorder of CD18 needed for INTEGRIN formation > leukocyte adhesion

  1. recurrent skin/mucosal infection - Staph, gram-neg rods, periodontal infections
  2. NO PUS - neutrophils cant extravasate
  3. Poor wound healing
  4. DELAYED UMBILICAL SEPARATION (>21 days)

labs show peripheral LEUKOCYTOSIS with NEUTROPHILIA

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7
Q

IL-12

A

produced by MACROPHAGES to stimulate Th1 differentiation

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8
Q

IL-4

A

produced by non-macrophage APCs to stimulate Th2 differentiation

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9
Q

Hereditary Angioedema

cause? mech of edema?

A

C1 inhibitor deficiency > uninhibited cleavage of C2/C4 by C1

also uninhibited conversion of KININOGEN to BRADYKININ > increased permeability + edema

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10
Q

serum levels of what are used to support clinical dx of anaphylaxis?

A

TRYPTASE, a relatively mast cell-specific enzyme

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11
Q

anaphylaxis tx (3 things, most important first)

A

IM epinephrine

airway management + volume resuscitation

supportive drugs - anti-HA and steroids

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12
Q

NK cells

surface molecules
how are they activated? (molecules, organs)
antigen specificity?

A

CD16 or CD56

activated by IFN-y or IL-12 (do NOT require thymus for activation, present in athymic pts; innate immunity)

NOT antigen specific

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13
Q

Graft Versus Host Disease

MCC?

other causes?

A

allogeneic bone marrow transplant

lymphocyte rich organ transplant (LIVER)
NON-IRRADIATED transfusions

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14
Q

Mechanism of GVHD

A

donor T cells migrate into tissues and recognize host MHC antigens as foreign + become sensitized

CD4 and CD8 cells destroy host cells

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15
Q

main organs affected in GVHD

A

SKIN - early sign is diffuse maculopapular rash (PALMS/SOLES) that may DESQUAMATE

GI tract - diarrhea, bleeding, pain

Liver - abnormal LFTs

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16
Q

what are is the preferred dx method for chronic granulomatous disease (CGD)?

(preferred over what?)

A

DHR FLOW CYTOMETRY - measures conversion of dihydrorhodamine (DHR) to rhodamine, a fluorescent green compound > low fluorescence = positive

(Nitroblue tetrazolium testing - add NBT to pt neutros > functioning neutros make ros that changes yellow NBT to dark blue formazan)

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17
Q

Organs most involved in CGD?

infection manifestations most common in CGD?

A

lungs, skin, nodes + liver

Pneumonia
Skin/organ abscesses
suppurative adenitis
osteomyelitis

all via CATALASE-POSITIVE organisms

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18
Q

2nd most common cause of SCID?

inheritance and cellular changes?

A

Adenosine Deaminase deficiency

AR inheritance

major decrease in T and B cells; variable immunoglobulin deficiency

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19
Q

IL-8 function

A

released by MACROPHAGES and ENDOTHELIUM in infections…

acts as a NEUTROPHIL CHEMOATTRACTANT and induces phagocytosis via neutrophils

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20
Q

C3a, 4a and 5a are all “anaphylatoxins” that trigger HA release > vasodilation + permeability…

what else do they do? (individually)

A

C3a - recruits + activates EOSINOPHILS + BASOPHILS

C5a - also recruits eos/basos, plus NEUTROPHILS + MONOCYTES

(C4a idk… wasnt mentioned)

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21
Q

IL-3 function

A

made by activated T cells

stimulates growth/diff of BM stem cells

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22
Q

LTC4 / D4 / E4 do what?

A

trigger vasoconstriction, permeability and BRONCHOCONSTRICTION

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23
Q

LTB4 (plus LT precursor 5-HETE) does what?

A

stimulates neutrophil migration

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24
Q

myeloperoxidase deficiency

common manifestations? differential for CGD? what can MPO defic neutrophils not produce?

A

often asymptomatic

CANDIDA infections are most common

diff dx - MPO defic pt has a NORMAL (“positive” - turns blue) NBT test, whereas CGD has a “negative” test that stays yellow

can’t produce “hydroxy-halide” (H-Cl-O, “bleach”)

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25
Q

cytokines released by virally infected cells that induce synthesis of antiviral proteins in nearby cells

A

interferon alpha and beta

limit viral spread by suppressing REPLICATION and ASSEMBLY

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26
Q

Selective IgA Deficiency

Epidemiology?

S/S + comorbidities (3)?

Labs (2)?

A

1 primary immunodeficiency

usually asymptomatic

  • recurrent SINOPULMONARY + GI INFECTIONS
  • AUTOIMMUNITY (Celiac, etc.)
  • TRANSFUSION ANAPHYLAXIS - react against donor IgA
  • Low/absent serum IgA
  • Normal IgG + IgM
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27
Q

Receptor for IL-8

what is it? on what cell?

A

CXCR1/2

on neutrophils

(IL-8 is neutrophil chemoattractant “cleanup on aisle 8”)

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28
Q

What causes induration at the site of a bee sting after the development of urticaria?

A

MACROPHAGES are attracted to the area and produce IL-1, IL-6 and TNF-a

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29
Q

Chediak-Higashi

inheritance, gene + affected process

A

AR defect of LYST lysosomal trafficking regulator

microtubule dysfunction in phagolysosome fusion

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30
Q

Chediak-Higashi

sx mnemonic (5)

A

PLAIN

Progressive neurodegen
Lymphohistiocytosis
Albinism (partial oculocutaneous)
Infections - recurrent pyogenic
Neuropathy
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31
Q

Chediak Higashi

clinical findings (3)

A

GIANT GRANULES in plts/granulocytes
Pancytopenia
Mild coagulation abnormalities

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32
Q

Early Complement Deficiency (C1, C2 and C4 defic.) can predispose to what AI disease?

A

SLE

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33
Q

Where on immunoglobulins does complement bind?

A

on the HEAVY CHAIN just proximal (closer to Fc end) of the hinge region / disulfide bonds

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34
Q

On IgM / IgA what structure enables formation of pentamers / dimers?

Where does it bind?

A

J chain

binds in the FcR binding region

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35
Q

What is IPEX?

gene? inheritance?

A

Immune dysregulation Polyendocrinopathy Enteropathy X-linked syndrome

defic. of FOXP3

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36
Q

IPEX

presentation?
3 main issues (+examples)

A

diabetes in a male infant, plus…

  1. Enteropathy
  2. AI derma issues - nail dystrophy, dermatitis, etc.
  3. Other Endocrinopathies
37
Q

What are the live, attenuated vaccines?

mnemonic

A

“Attention! Please Vaccinate Small, Beautiful Young Infants with MMR Regularly!”

  • Adenovirus (actually non-attenuated, for military)
  • Polio (sabin)
  • Varicella
  • Smallpox
  • BCG
  • Yellow fever
  • Influenza (intranasal form)
  • MMR
  • Rotavirus
38
Q

When can MMR and varicella vaccines be given to HIV pts?

A

if they do not have evidence of immunity to these microbes and…

CD4 of AT LEAST 200/mm3

39
Q

Diff btwn immune responses evoked by live vs. killed vaccines

A

live - humoral and cellular

killed - mainly humoral

40
Q

What are the killed/inactivated vaccines?

A

“RIP Always”

  • Rabies
  • Influenza (injection form)
  • Polio (Salk)
  • Hepatitis A

(SalK = Killed)

41
Q

What are the subunit vaccines?

(a mnemonic for 3, plus two others)

pros + cons?

A

the SHiN organisms:

  • S. pneumo
  • H. flu
  • Neisseria meningitidis
  • HBsAg
  • HPV 6, 11, 16, 18

Pro - fewer adverse rxns
Cons - more expensive + weaker immune responses

42
Q

What are the 2 toxoid vaccines?

A

Clostridium tetani

C. diphtheriae

43
Q

T2 HS rxns involved Abs binding cell surface antigens…

What are 4 examples of T2 HS rxns in which the Ab binding results in CELLULAR DESTRUCTION?

(via opsonization > phagocytosis, complement activation, or ADCC via NK cells)

A
  1. Autoimmune Hemolytic Anemia
  2. Immune thrombocytopenia (Gp IIb/IIIa)
  3. Transfusion reactions
  4. Hemolytic newborn diseases
44
Q

What are 3 examples of T2 HS rxns in which the Ab binding results in INFLAMMATION via complement activation + Fc-receptor mediated inflammation?

(as opposed to total cellular destruction)

A
  1. Goodpasture syndrome
  2. Rheumatic fever (M protein cross reactivity)
  3. HYPERACUTE transplant rejection
45
Q

What are 3 examples of when T2 HS rxns result in CELLULAR DYSFUNCTION?

A
  1. Myasthenia Gravis
  2. Graves
  3. Pemphigus vulgaris
46
Q

T3 HS rxns are mediated by Ag-Ab-complement complexes…

what cell type then mediates most of the damage?

A

Neutrophils

attracted by complexes and release lysosomal enzymes

47
Q

What are 3 examples of T3 HS rxns?

think systemic, vascular and renal

A
  1. SLE
  2. Polyarteritis nodosa
  3. PSGN
48
Q

What is the “prototype” immune complex disease (ie, T3 HS rxn)?

How does it occur?

What triggers is it associated with (2 categories + examples)?

A

Serum Sickness

Abs to foreign proteins produced and ONE TO TWO WEEKS LATER, complexes form and DEPOSIT in tissues > complement activation, inflamm. + damage

  1. Drugs - act as haptens, ex: PENICILLINS
  2. Infections - ex: HEP B
49
Q

1-2 weeks after Ag exposure…

what are the sx that occur in serum sickness (5)?

A
  1. Fever
  2. Urticaria
  3. Arthralgia
  4. Proteinuria
  5. LAP
50
Q

What is a local, dermal form of T3 HS rxn?

What is required for it to occur?

what 2 things happen locally?

A

Arthus reaction

intradermal injection of Ag into a PRESENSITIZED (pt already has IgG against it) causes INTRADERMAL COMPLEX FORMATION

edema, necrosis + complement activation

51
Q

what are the 2 mechs in T4 HS rxn?

A

Both involve T cells

  1. CD8 cytotoxicity
  2. CD4 release inflammatory cytokines

Is the only of the 3 HS rxns that does NOT involve antibodies!

52
Q

What type of transplant issue is a T4 HS rxn?

A

Graft versus host disease

53
Q

What are the 4 types of BLOOD TRANSFUSION REACTIONS in order of how early/late they would happen post transfusion?

A
  1. Allergic/Anaphylactic - from minutes to 3 hours
  2. Acute hemolytic - within 1 hour
  3. Febrile nonhemolytic - btwn 1-6 hours
  4. Acute Lung Injury - within 6 hours
54
Q

WHAT ANTIGEN (general) in the transfused blood is bound by IgE in an ANAPHYLACTIC/ALLERGIC transfusion rxn?

What consequence does this have for transfusions in patients with a certain humoral immune deficiency?

A

Donor PLASMA PROTEINS (as opposed to cell surface antigens)

IgA deficient pts must receive IgA-FREE BLOOD PRODUCTS or they would react to the IgA

55
Q

What is the mechanism for FEBRILE NONHEMOLYTIC transfusion reactions? (2 parts)

A

Within 1-6 hrs pt has fever, headache, chills + flushing via…

  1. T2 HS rxn of host Abs against donor HLA or WBC
  2. CYTOKINES that are created + accumulate in blood during storage
56
Q

What are the 2 possible mechanisms in ACUTE HEMOLYTIC transfusion reactions?

How do symptoms differ depending on the mechanism?

A

Within 1 hour, pt will have fever, hypotension, tachypnea/-cardia with…

  1. INTRAVASCULAR lysis - via ABO incompatibility; also includes sx of FLANK PAIN and HEMOGLOBINURIA
  2. EXTRAVASCULAR lysis - via host Ab against donor rbc surface Ag; includes JAUNDICE
57
Q

What is the mechanism of TRANSFUSION-RELATED ACUTE LUNG INJURY?

A

DONOR ANTIBODIES against RECIPIENT NEUTROs and PULMONARY ENDOTHELIUM

resp distress and non-CV pulmonary edema within 6 hrs

58
Q

X-linked agammaglobulinemia

defect? chromosome?

general presentation?

A

an X-linked defect in BTK (Bruton tyrosine kinase)

no B-cell maturation (Bruton, B cells, Boys)

recurrent BACTERIAL and ENTEROVIRAL infections after 6 months when maternal IgG is gone

59
Q

X-linked agammaglobulinemia

blood findings (2)? anatomical findings?

preventative tx contraindications?

A 
Low Ig (all classes)
No B cells

Small/no lymph nodes or tonsils

LIVE vaccines are CI

60
Q

Common variable immunodef.

what is the general defect?
when does it present?

A

defect in B-CELL DIFFERENTIATION

presents AFTER 2 YEARS but may be delayed

61
Q

Common variable immunodef.

Increases risk of what 4 things?

Blood findings?

(if you think of the defect in B-CELL differentiation, the TYPE of infections is hinted at, and the type of infection hints at another risk… and if you consider that it’s DIFFERENTIATION, a 3rd risk is hinted at)

A
  1. SINOPULMONARY infections
  2. Bronchiectasis
  3. Lymphoma
  4. Autoimmunity

decreased PLASMA CELLS and Ig

62
Q

Deletion and developmental failure in DiGeorge

A

22q11 deletion

failed dev. of THIRD and FOURTH pharyngeal POUCH

(parathyroid and thymus affected)

63
Q

3 main signs/sx in DiGeorge

think serum, immunity and CV

A
  1. hypocalcemia with TETANY
  2. VIRAL + FUNGAL infections - T-cell def.
  3. “conotruncal” issues such as FALLOT or TRUNCUS ARTERIOSUS
64
Q

If other pharyngeal pouches are involved in DiGeorge, what MORPHOLOGICAL sx might you see?

A

if 1st/2nd phar. pouch involved…

hypertelorism - eyes far apart
short palpebral fissures
micrognathia - small jaw
bifid uvula
cleft palate
65
Q

What immune deficiency is specifically a Th1 response deficiency?

Inheritance? Types of infections? Serum?

A

IL-12 receptor deficiency - with AR inheritance

severe FUNGAL and MYCOBACTERIAL infections that MAY PRESENT AFTER BCG vaccine

low IFN-y

66
Q

What T-cell disorder presents with high IgE?

Inheritance, gene + defect?

A

“Autosomal Dominant Hyper-IgE Syndrome” or Job syndrome

deficient TH17 response due to STAT3 mutation causes…

IMPAIRED NEUTROPHIL RECRUITMENT

67
Q

what are the features of Job syndrome / autosomal dominant hyper-IgE syndrome?

(mnemonic with 6 items)

A

Be FATED to do your Job

Bone - fractures via minor trauma

  1. Face - coarse features
  2. Abscesses - “cold” uninflamed Staph (no neutros)
  3. Teeth - primary teeth retained
  4. Eosinophils and IgE - elevated
  5. Derma - eczema etc.
68
Q

Aside from HIV and immunosuppressant tx…

what immune deficiency can cause Candida infections of the skin and mucosa?

what is the congenital defect? diagnostic tests (2)?

A

“Chronic Mucocutaneous Candidiasis”

a T-cell defect due to IL-17 or IL-17R defect

NONINVASIVE Candida infections of skin/mucosa

  1. IN VITRO T cell response to Candida is low
  2. CANDIDA SKIN TEST is negative (similar to PPD)
69
Q

SCID

2 common types/defects and their inheritance

A
  1. IL-2R gamma chain defect - most common, XR
  2. Adenosine deaminase defic. - AR

(Guys have Gamma chain issue
Adenosine deaminase is Autosomal)

70
Q

SCID presentation

3 items (systemic, GI and oral)

A
  1. Failure to thrive
  2. Chronic diarrhea
  3. Thrush

recurrent infections with EVERYTHING - fungi, protozoa, viruses, bacteria

71
Q

SCID treatment

curative (1) vs. preventative (2)

contraindications

A

BM transplant is curative (no rejection!)

Abx prophylaxis + IVIG

LIVE vaccines are CI

72
Q

Lab (2), imaging (1) and biopsy (1) findings in SCID

A
  1. Low TCR “excision circles” - small DNA circles in t cells as they pass thru thymus + rearrange DNA
  2. No T cells on FCT
  3. Absent thymic shadow
  4. Nodes have NO GERMINAL CENTERS
73
Q

What is the immune deficiency in Ataxia Telangiectasia?

the name, gene, SERUM FINDING, immune def. and other symptoms all follow a memory hook!

A

Autosomal recessive ATM gene issue > Ataxia, spider Angiomas and…

IgA deficiency (also IgG and IgE, apparently…)

high AFP in serum

remember the As

74
Q

what cancers are Ataxia Telangiectasia pts at increased risk of?

A

Leukemias and lymphomas

75
Q

Hyper-IgM syndrome

what is the defect? inheritance?

A

defective CD40L on Th cells causes CLASS SWITCHING issues

XR

76
Q

Hyper-IgM syndrome

presentation?
3 specific organisms

A

SEVERE PYOGENIC infections EARLY in life

  1. Pneumocystis jirovecii
  2. Cryptosporidium parvum
  3. CMV

NO GERMINAL CENTERS; IgM is high, all other Igs low

77
Q

Which immune deficiency is specifically an ANTIGEN PRESENTATION defect?

Specific defect + inheritance?

A

Wiskott-Aldrich syndrome

WASp gene defect via XR

WBCs and PLTs can’t detect actin cytoskeleton > Ag presentation issues

78
Q

Wiskott-Aldrich syndrome

mnemonic for 3 issues

increased risks?

A

WATER = Wiskott-Aldrich +

  1. Thrombocytopenia - with bloody diarrhea!
  2. Eczema
  3. Recurrent pyogenic infection

incr. risk of AI disease and cancer

79
Q

Wiskott-Aldrich

Ig abnormalities (some high, some low)? cell counts?

A

low-to-normal IgG/M

HIGH IgE and IgA

fewer + smaller PLTs

80
Q

Leukocyte Adhesion Deficiency (type 1)

defect + inheritance?

A

LFA-1 integrin (CD18) on phagocytes

impairs migration + chemotaxis

AR inheritance

81
Q

Leukocyte Adhesion Deficiency

presentation (infection type + special characteristic of infection; special birth-related sign)

A

Recurrent SKIN + MUCOSA BACTERIAL infections with NO PUS!

Impaired wound healing

LATE CORD SEPARATION (>30 days)

high neutros in blood, low neutros at infection sites

82
Q

How does IkB regulate NF-kB?

A

binds it and prevents its translocation to nucleus

then IKK (IkB kinase) will P-ate IkB when an extracellular signal (eg, IL-1 binding IL-1R) activates it…. IkB releases NF-kB and it can translocate to nucleus

83
Q

T-cells within thymic cortex express…

2 things (note: not asking about CD molecules)

A

Class I MHC

Rearranged D and J segments of the TCR beta chain

84
Q

Unique AA in bacterial peptides that can act as a PAMP?

how?

A

N-formyl-methionine

activates WBCs by binding their “formyl peptide receptors” which are GPCRs

85
Q

an infant with SCID has severe anemia

what transfusion product should he be given?

A

IRRADIATED PACKED RBCs

not whole blood!

86
Q

2 types of pneumococcal vaccines

A

PPSV23 - polysaccharide 23-valent

PCV13 - conjugate 13-valent with diphth toxoid

87
Q

Who gets the polysacch-23 vs. the conjugate-13 valent pneumococcal vaccines?

A

polysacch-23 is given to ADULTS > 65 and anyone 2-64 with DM, or chronic LUNG/CV disease

conjugate-13 is given to KIDS < 2, anyone who is IMMUNOCOMPROMISED and ADULTS > 65

88
Q

Functional differences between…

23-valent polysaccharide

vs.

13-valent conjugate pneumococcal vaccines

A

Polysacch - wider serotype range; titers decline over 5 years; not immunogenic in kids <2 due to immature humoral immunity; overall MODERATE AMOUNT of INTERMEDIATE-AFFINITY Abs

Conjugate - diphtheria toxoid > T AND B-CELL recruitment > higher levels of higher affinity Abs with LESS MUCOSAL CARRIAGE (herd immunity)

*USMLE* (28 decks)

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