Immunodeficiency Flashcards

1
Q

Severe Combined Immunodeficiency Disorder (SCID)

A

Early developmental block of immune system, lymphopenia of both B- and T-cells, more than half of these diseases are X-linked recessive, other SCIDs are autosomal recessive

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2
Q

SCID-X1

A

Most common of the SCIDs, defect is in the gene for the gamma chain that forms part of the receptors for IL-2 and other cytokines necessary for lymphoid development, or their signaling pathways

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3
Q

Autosomal recessive SCID

A

Patients lack the enzyme adenosine deaminase (ADA); so adenosine accumulates in all cells but impairs lymphocyte development selectively

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4
Q

X-Linked (Bruton) Agammaglobulinemia

A

Normal T-cells but low or no B-cells (& Abs), developmental block from Pre-B-cell to B-cell, tyrosine kinase gene defective, bacterial infections manifesting in pneumonia and chronic diarrhea, oral polio vaccine could revert to infect these kids

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5
Q

X-Linked Hyper IgM Syndrome

A

CD40 on B-cell or CD40-Ligand on Tfh defective, Tfh cells can’t help B-cells with Ig class-switching, lots of IgM and very little IgG or IgA.

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6
Q

Common Variable Immunodeficiency (CVID)

A

Group of conditions, Can see innate immunity as well as B and T cell defects, low serum IgG, recurrent bacterial infections, treated with IVIG or SCIG

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7
Q

DiGeorge Syndrome

A

3rd/4th pharyngeal pouches do not develop correctly, thymus cannot develop, absent T-cells with normal B-cells, Cell-mediated immunity is depressed, viral and fungal infections are common, large deletion (45-gene) on chromosome 22, parathyroids are also derrived from the same embryonic tissues thus patient may present in infancy with convulsions controllable with calcium, great vessels of heart develop abnormally

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8
Q

CATCH-22

A

DiGeorge Syndrome: defect on chromosome 22.
Calcium: can’t develop parathyroid properly, seizures. Appearance: facial development affected.
Thymus: decrease of T-cells.
Clefts: cleft palate common.
Heart: defects in great vessels of heart.

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9
Q

Associations with T-cell deficiencies

A

Severe infections with intracellular pathogens i.e. viruses, certain bacteria, yeasts, and fungi, especially Candida albicans and Pneumocystis jirovecii

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10
Q

Associations with B-cell deficiencies

A

Infections with extracellular, pyogenic (“high-grade”) bacterial pathogens, e.g. Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae

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11
Q

Transient Hypogammaglobulinemia of Infancy

A

Noticed about 6 mo after birth and can last up to 18 mo of age (sometimes longer). Slow to get IgG production going, recurrent and persistent gram-positive bacterial infections, perhaps 15% of all chronic diarrhea in infants is due to this condition.

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12
Q

Selective IgA Deficiency

A

Most common immunodeficiency disease, usually asymptomatic, may have diarrhea and sinopulmonary infections, or an increased frequency and severity of allergies, runs in families, 10-15x more likely if patient has celiac disease.

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13
Q

Ataxia Telangiectasia

A

autosomal recessive disease characterized by sinus infections and pneumonia, ataxia (staggering) and telangiectasia (dilated abnormal blood vessels). There is both T and B cell deficiency, not absolute; IgA is especially depressed. There is also an interesting defect in DNA repair which may partially explain the extraordinary incidence of tumors in these patients.

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14
Q

Wiskott-Aldrich syndrome

A

Platelet and B cell deficiency, eczema, and many bacterial infections. It is X-linked.

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15
Q

Especially immunosuppressive Viral illnesses

A

Measles, mononucleosis, and cytomegalovirus (CMV) infection–secondary infection is common. Acquired Immune Deficiency Syndrome (AIDS) is the most serious condition involving secondary immunodeficiency.

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16
Q

Treatment of Immunodeficiencies

A
  1. Isolation i.e. bubble–impractical.
  2. Prophylactic antibiotics, must change regularly due to antibiotic resistance.
  3. Human immunoglobulin, where B cell function is deficient. IVIG most common, but expensive. Slow subcutaneous infusion (SCIG) may also be a possibility.
  4. Transplantation. In DiGeorge, fetal thymus or cultured thymic stromal cells (Donor’s) have been used to try to minimize the risk of graft-versus-host disease, T-cells are patient’s own.
17
Q

Treatment for SCID

A

Bone marrow transplantation has about a 50% success rate, but graft-versus-host disease is always a problem. It is better to transplant purified stem cells than whole bone marrow. Sibling donors are the best, and a good Class II MHC match is imperative. For ADA- deficient patients, transfusions of irradiated red cells can be helpful.

18
Q

Working up defective immunity: Initial tests for B-cells

A

Serum protein electrophoresis; Quantitative IgG, IgA, IgM levels;􏰀 Specific Abs to prior immunizations;􏰀 ABO isohemagglutinins

19
Q

Working up defective immunity: Advanced tests for B-cells

A

Ab responses to novel Ags;􏰀 Sequence suspect genes;􏰀 Lymph node biopsy

20
Q

Working up defective immunity: Initial tests for T-cells

A

Skin test with recall Ag panel;􏰀 Total lymphocyte count;􏰀 CD3, CD4, CD8 counts

21
Q

Working up defective immunity: Advanced tests for B-cells

A

Mitogen responses, MLR, cytokine measurements;􏰀 Sequence suspect genes

22
Q

Working up defective immunity: Initial tests for Phagocytes

A

WBC count, differential, morphology;􏰀 NBT test, oxidative burst

23
Q

Working up defective immunity: Advanced tests for Phagocytes

A

Assays for phagocytosis, chemotaxis; Sequence suspect genes

24
Q

Working up defective immunity: Initial tests for Complement

A

CH50; Assay for C1inh (inhibitor)

25
Q

Working up defective immunity: Advanced tests for Complement

A

Individual complement component levels