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ABSITE > 4 Immunology : 5 Infection > Flashcards

4 Immunology : 5 Infection Flashcards

1
Q

What do helper T-cells (CD4) release?

A

IL2, IL4

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2
Q

Interleukin that causes maturation of cytotoxic T cells?

A

IL-2

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3
Q

Interleukin that causes B-cells maturation into Plasma cells?

A

IL-4

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4
Q

Which cells are involved in delayed hypersensitivity reactions?

A

Helper T-cells (CD4)

Brings in inflammatory cells by chemokine secretions (Type 4 hypersensitivity)

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5
Q

What cells regulate CD4 and CD8 cells?

A

Suppressor T-cells (CD8)

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6
Q

What recognizes and attacks non-self-antigens attached to MHC class I receptors?

A

Cytotoic T-cells (CD8)

I.e. viral gene products

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7
Q

How do you test cell-mediated immunity?

A

Intradermal skin test (i.e. TB test)

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8
Q

What infections are associated with defects in cell-mediated immunity?

A

Intracellular pathogesn (TB, viruses)

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9
Q

Characteristics of MHC class I (A, B, C)

A

CD8 activation (suppressor, cytotoxic)
Present on ALL nucleated cells
Single chain with 5 domains
Target for cytotoxic T-cells (binds T-cell receptors)

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10
Q

Characteristics of MHC class II (DR, DP, DQ)

A

CD4 cell activation (helper)
Present on antigen-presenting cells (i.e. monocytes, dendrites)
2 chains with 4 domains each
Activates helper T-cells (binds T-cell receptor)
Stimulates antibody formation after interaction with B-cell surface IgM

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11
Q

Effect of viral infection on immune response?

A

Endogenous viral proteins are produced
Bound to class I MHC
Go to cell surface
Recognized by CD8 cytotoxic T-cells

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12
Q

Effect of bacterial infection on immune response?

A

Endocytosis
Proteins get bound to class II MHC molecules
Go to cell surface
Recognized by CD4 helper T-cell

B-cells that are already bound to the antigen are then activated by CD4 helper T-cells
They produce the antibody to that antigen and are transformed to plasma cells and memory B-cells

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13
Q

Characteristics of natural killer cells

A

Not restricted by MHC, do not require previous exposure, do not require antigen presentation
Not considered T or B cells
Recognize cells that lack self-MHC
Part of the body’s natural immunosurveillance for cancer

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14
Q

IgM

A 
Initial antibody made after exposure to antigen
Larges antibody (5 domains, 10 binding sites)
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15
Q

IgG

A

Most abundant antibody in body
Responsible for secondary immune response
Can cross the placenta and provides protection in newborn period

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16
Q

T-cell and B-cell activation?

A

Two signals are required
First - alloantigen binds to antigen-specific receptors (TCR - T-cells; surface IgM - B-cells)
Second - costimulation via IL-1 (released by antigen-presenting cells)

CD4 helper T-cells release IL-2, IL-4, which provide help for CD8 t-cells and B-cell activation

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17
Q

How are endogenously synthesized or intracellular proteins processed?

A 
Degraded into peptides, transported to the ER
Bind to class I MHC molecules and are transported to the surface of the antigen-presenting cells
CD8 cells recognize the foreign peptide bound to Class I MHC via TCR complex
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18
Q

How are exogenous antigens processed?

A

Endocytosed and broken down into peptide fragments in endosomes
Class II MHC molecules are transported to the endosome, bind the peptide and are delivered to the surface of the antigen-presenting cell, where they are recognized by CD4 cells

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19
Q

IgA

A

Found in secretions
In Peyer’s patches in gut
In breast milk
Help prevents microbial adherence and invasion in gut

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20
Q

IgD

A

Membrane-bound receptor on B-cells

Serves as an antigen receptor

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21
Q

IgE

A

Allergic reactions

Parasite infections

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22
Q

Which immunoglobulins are osponins?

A

Makes antigen for immune response

IgM, IgG

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23
Q

Which immunoglobulins can fix complement?

A

IgM (1) or IgG (2 needed)

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24
Q

What is the role of the variable region?

A

Antigen recogniztion

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25
Q

What is the role of the constant region?

A

Recognized by PMNs and Macrophages

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26
Q

Type I hypersensitivity reaction?

A

Immediate hypersensitivity reaction (allergic)
Eosinophils with IgE receptors - release major basic program –> activates mast cells and basophils –> release histamine, serotonin, bradykinin
(Bee stings, peanuts, hay fever)

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27
Q

Type II hypersensitivity reaction?

A

IgG or IgM reacts with cell-bound antigen

ABO blood incompatibility, Graves disease, myasthenia gravis

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28
Q

Type III hypersensitivity reaction?

A

Immune complex deposition

Serum sickness, SLE

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29
Q

Type IV hypersensitivity reaction?

A

Delayed-type hypersensitivity
Antigen stimulation of previously sensitized T-cells
(TB skin test, contact dermatitis)

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30
Q

Major source of histamine in blood?

A

Basophils

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31
Q

Major source of histamine in tissues?

A

Mast cells

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32
Q

Primary lymphoid organs?

A

Liver, bone, thymus

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33
Q

Secondary lymphoid organs?

A

Spleen, lymph nodes

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34
Q

Function of IL-2?

A

Converts lymphocytes to lymphokine-activated killer cells (LAK) by enhancing their immune response to tumor
Converts lymphocytes into tumor-infiltrating lymphocytes
Helpful in melanoma

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35
Q

Tetanus prophylaxis? Non-tetanus-prone wounds

A

Give tetanus toxoid only if patient has received <3 doses or tetanus status is unknown

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36
Q

Tetanus prophylaxis? Tetanus-prone wounds

A

(>6 hours old, obvious contamination, devitalization; crush, frostbite, burn or missile injuries)
Always give tetanus toxoid

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37
Q

When do you give tetanus immune globulin?

A

Tetanus-prone wounds in patients who have not been immunized or if immunization status is unknown

38
Q

Microflora of the stomach?

A

Virtually sterile

Some GPCs, some yeast

39
Q

Microflora of the proximal small bowel?

A

10^5 bacteria

Mostly GPCs

40
Q

Microflora of the distal small bowel?

A

10^7 bacteria

GPCs, GPRs, GNRs

41
Q

Microflora of the colon?

A

10^11 bacteria

Almost all anerobes, some GNRs, GPCs

42
Q

Most common anaerobe in colon?

A

Bacteroides fragilis

43
Q

Most common aerobic bacteria in the colon?

A

Escherichia coli

44
Q

Most common source of fever within 48 hours post-op?

A

Atelectasis

45
Q

Most common source of fever within 48 hours - 5 days post-op?

A

Urinary tract infection

46
Q

Most common source of fever > 5 days post-op?

A

Wound infection

47
Q

Most common cause of gram negative sepsis?

A

E. coli

48
Q

E. coli endotoxin - characteristics?

A

Lipopolysaccharide lipid A

Triggers release of TNF-a from macrophages, activates complement, activates coagulation cascade

49
Q

Response of insulin and glucose to gram-negative sepsis?

A

Early - decreased insulin, increased glucose (impaired utilization)
Late - increased insulin, increased glucose (insulin resistance)

50
Q

Optimal glucose level in a septic patient?

A

100-120mg/dL

51
Q

When do abscesses occur post-operative?

A

7-10 days

52
Q

When do you give antibiotics for abscesses?

A

Patients with diabetes, cellulitis, clinical signs of sepsis, fever, elevated WBC or bioprosthetic hardware

53
Q

Risk of surgical site infection in clean cases? (i.e. hernia)

A

2%

54
Q

Risk of surgical site infection in clean contaminated cases? (i.e. elective colon resection in prepped bowel)

A

3-5%

55
Q

Risk of surgical site infection in contaminated cases? (GSW to colon with repair)

A

5-10%

56
Q

Risk of surgical site infection in gross contamination cases? (Abscess)

A

30%

57
Q

Why do we give prophylactic antibiotics? When do we stop them?

A

To prevent surgical site infections

Stop within 24 hours of end of operation (48hrs for cardiac cases)

58
Q

Most common organism in surgical wound infections?

A

Staphylococcus aureus (coagulase-positive)

59
Q

Coagulase-negative gram positive cocci

A

Staphylococcus epidermidis

60
Q

Most common GNR in surgical wound infections?

A

E. coli

61
Q

Most common anerobe in surgical wound infections?

A

B. fragilis

Indicates necrosis or abscess - cannot survive in oxygenated tissue

62
Q

Number of bacteria required for a wound infection?

A

> 10^5 bacteria (less if there is hardware)

63
Q

Risk factors for wound infection?

A 
Long operation
Hematoma or seroma formation
Advanced age
Chronic disease (i.e. COPD, renal failure, liver failure, DM)
Malnutrition
Immunosuppresive drugs
64
Q

Causes of surgical infections within 24 hours post-op?

A

Injury to bowel with leak

Invasive soft tissue infection (C. perfringes, B-hemolytic strep)

65
Q

Most common infection in surgical patients?

A

Urinary tract infections
Secondary to foleys
Most commonly E. coli

66
Q

Leading cause of infectious death after surgery?

A

Nosocomial pneumonia

Related to length of intubation and aspiration

67
Q

Most common organisms in ICU pneumonia?

A

S. aureus

Pseudomonas

68
Q

Causes of line infections?

A

S. epidermidis
S. aureus
Yeast

69
Q

Causes of necrotizing soft tissue infections?

A

Beta-hemolytic streptococcus
C. perfringens
Mixed organism

70
Q

Findings of necrotizing soft tissue infections?

A 
Pain out of proportion to skin findings
WBCs >20
Thin gray drainage
Can have skin blistering/necrosis
Induration and edema
Creptus or soft tissue gas on x-ray
Can be septic
71
Q

Treatment of necrotizing fasciitis?

A

Early debridement

High-dose penicillin

72
Q

When do you need fungal coverage?

A 
Positive blood cultures
2 sites other than blood
1 site with severe symptoms
Endophthalmitis
Patient on prolonged antibiotics with no improvement
73
Q

Characteristics and treatment: Actinomyces?

A

Pulmonary symptoms most common; causes abscesses

Drainage and penicillin G

74
Q

Characteristics and treatment: Nocardia?

A

Pulmonary and CNS symptoms

Drainage and sulfonamides (bactrim)

75
Q

Characteristics and treatment: Candida?

A

Inhabits the respiratory tract

Fluconazole, anidulafungin for severe infections

76
Q

Characteristics and treatment: Aspergillosis?

A

Voriconazole for severe infections

77
Q

Characteristics and treatment: Histoplasmosis?

A

Pulmonary symptoms; MIssissippi and Ohio River valley

Liposomal amphotericin for severe infections

78
Q

Characteristics and treatment: Cryptococcus?

A

CNS symptoms, AIDS patients

Liposomal amphotericin for severe infections

79
Q

Characteristics and treatment: Coccidioidomycosis?

A

Pulmonary symptoms; Southwest

Liposomal amphotericin for severe infections

80
Q

HIV exposure risk: blood transfusion?

A

70%

81
Q

HIV exposure risk: infant from positive mother?

A

10%

82
Q

HIV exposure risk: needle stick from positive patient?

A

0.3%

83
Q

HIV exposure risk: Mucous membrane exposure?

A

0.1%

84
Q

Medications to decrease seroconversion after exposure?

A

AZT (zidovudine, reverse transcriptase inhibitor), ritonavir (protease inhibitor)

85
Q

Upper GI bleed in HIV patient?

A

Kaposi’s sarcoma*

Lymphoma

86
Q

Lower GI bleed in HIV patient?

A

CMV*
Bacterial
HSV

87
Q

CD4 counts and associated symptoms?

A

800-1200 normal
300-400 symptomatic disease
<200 opportunistic infections

88
Q

Brown recluse spider bites

A

Treat with dapsone, may need to resect and then skin graft

89
Q

Acute septic arthritis

A

Gonococcus, staph, H. influenzae, strep

Treat with drainage, 3rd-gen cephalosporins, vanco

90
Q

Diabetic foot infection

A

Mixed staph, strep, GNRs, anaerobes

Broad-spectrum antibiotics (Unasyn)

91
Q

Eikenella

A

Only found in human bites - can cause permanent joint injury

Treat with Augmentin

92
Q

Pasteurella multocida

A

Found in cat and dog bites

Treat with Augmentin

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