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Immunology > Immunodeficiency Diseases > Flashcards

Immunodeficiency Diseases Flashcards

1
Q

Disorders in which a part of the body’s immune system is missing or dysfunctional

A

Immunodeficiencies

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2
Q

Clinical symptoms associated with immunodeficiencies

A

Ranges from very mild or subclinical to severe, recurrent infections or failure to thrive

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3
Q

Two Types of Immunodeficiencies

A

Inherited and Acquired

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4
Q

Example of a secondary immunodeficiency

A

Acquired Immunodeficiency Syndrome (AIDS), which is caused by the
human immunodeficiency virus (HIV)

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5
Q

Affects primarily males

A

Immunodeficiency syndromes with X-linked inheritance

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6
Q

Exception to that primary immunodeficiencies (PIDs) are rare disorders with a combined incidence of about 1 in 1,200 live births

A

Immunoglobulin A (IgA) deficiency

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7
Q

Some PIDs have their primary effect on B cells and humoral immunity

A

whereas others mainly affect the cell-mediated branch of the adaptive immune system

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8
Q

In general, defects in humoral immunity (antibody production)

A

Results in pyogenic (i.e., pus-forming) bacterial infections, particularly of the upper and lower respiratory tract. Recurrent sinusitis and otitis media (i.e., ear infections) are common.

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9
Q

The clinical course of viral infections in patients with predominantly antibody deficiencies is not significantly different
from that in normal hosts, with the exception of _____

A

Hepatitis B, which may have a fulminant course in patients with agammaglobulinemias, conditions in which antibody levels in the blood are significantly decreased.

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10
Q

Defects in T-cell–mediated immunity result in

A

Recurrent infections with intracellular pathogens such as viruses, fungi, and
intracellular bacteria.

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11
Q

Patients with congenital T-cell deficiencies

almost always develop

A
  • Mucocutaneous candidiasis, a yeast infection that involves the skin, nails, and mucous membranes.
  • They are also prone to disseminated viral infections, especially with latent viruses such as herpes simplex, varicella zoster, and cytomegalovirus.
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12
Q

Because T cells also play an important role

in tumor immunity,

A

Patients with these conditions are more susceptible to developing certain types of cancer

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13
Q

Age-adjusted rates of malignancy in patients with immunodeficiency disease are

A

10 to 200 times greater than those observed in immunocompetent individuals

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14
Q

Most of the malignancies are

A

Lymphoid and may be related to persistent stimulation of the remaining immune cells, coupled with defective immune regulation.

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15
Q

Neutrophils are the first line of defense against invading organisms

A

Defects in neutrophil function are usually reflected in recurrent pyogenic bacterial
infections or impaired wound healing.

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16
Q

Abnormalities in macrophage function will have effects on ______

A

Both the innate and the adaptive defenses because macrophages are involved in the
nonspecific phagocytosis of microorganisms during inflammation as well as in the processing of antigens and their presentation to T cells in humoral and cell-mediated immune responses

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17
Q

Reduction in the macrophage population by splenectomy is associated with _____

A

An increased risk of overwhelming bacterial

infection accompanied by septicemia

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18
Q

The complement system is activated directly by antigens or by antigen–antibody complexes to produce biologically active
molecules that enhance inflammation and promote lysis of microorganisms.

A

Deficiencies of complement components result in recurrent bacterial infections and autoimmune-type manifestations. The severity of the conditions varies with the particular complement component that is deficient.

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19
Q

In many cases, it appears that deficiency of

one component of the immune system is accompanied by hyperactivity of other components

A

This may occur because persistent
infections continuously stimulate the available immune cells or because a compensatory mechanism has been activated to correct for the deficient immune function.

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20
Q

In addition, the deficiency may involve a component that normally exerts regulatory control over other components of the immune system—control that is lacking in the deficiency state. For instance, T helper (Th2) cells secrete cytokines that regulate the
development of B cells into plasma cells.

A

Defect in Th2 cell function, such as a deficiency in CD40L (a molecule involved in
binding to cell receptors during T-dependent immune responses), removes or creates an imbalance in the regulation of those immune
responses.

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21
Q

Whatever the mechanism, many partial immunodeficiency states are associated with allergic or autoimmune manifestations

A

Currently referred to as autoinflammatory disorders

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22
Q

The Nine Categories of Primary Immunodeficiencies (PIDs)

A
  • Category 1: Combined Immunodeficiencies
  • Category 2: Combined Immunodeficiencies With Associated or Syndromic Features
  • Category 3: Predominantly Antibody Deficiencies
  • Category 4: Diseases of Immune Dysregulation
  • Category 5: Congenital Defects of Phagocyte Number, Function, or Both
  • Category 6: Defects in Innate Immunity
  • Category 7: Autoinflammatory Disorders
  • Category 8: Complement Deficiencies
  • Category 9: Phenocopies of Primary Immunodeficiencies
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23
Q

In the past, the immunodeficiencies have been broadly classified as defects in T cells, B cells, phagocytes, complement proteins,
and other components of the innate immune system. As scientific knowledge has been gained about the complexity of these disorders, experts have recognized that such a broad classification is overly simplistic.

A

In 2014, the International Union of Immunologic Societies (IUIS) updated their classification of PIDs by grouping them into nine different categories based on their characteristic clinical features, immunologic defects, and genetic abnormalities. The IUIS has also published diagnostic flow charts to aid in classifying patients into a disease entity based on clinical symptoms and laboratory results.

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24
Q

The conditions in this category are the most common immunodeficiencies, representing about 50% of the PIDs

A

Category 3,

Predominantly Antibody Deficiencies

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25
Q

This category encompasses conditions in which the main characteristic is low levels of serum immunoglobulins

A

Category 3: Predominantly Antibody Deficiencies

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26
Q

Immunoglobulins migrate in the “gamma region” of the serum protein electrophoretic profile…

A

Therefore, deficiencies of immunoglobulins have been termed agammaglobulinemias

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27
Q

The mechanisms of the agammaglobulinemias include ____

A

Genetic defects in B-cell maturation or

mutations leading to defective interactions between B and T cells.

28
Q

Deficiency: All antibodies; especially IgG

Level of Defect: Slow development of helper
function in some patients

Presentation: 2–6 months; resolves by
2 years

A

Transient hypogammaglobulinemia of infancy

29
Q

Deficiency: IgA; some also with reduced
IgG2

Level of Defect: IgA-B cell differentiation

Presentation: Often asymptomatic

A

Selective IgA deficiency

30
Q

Deficiency: All antibody isotypes reduced

Level of Defect: Pre–B-cell differentiation

Presentation: Infancy

A

Btk deficiency

31
Q

Deficiency: Reduced antibody; many different
combinations

Level of Defect: B cell; excess T suppression

Presentation: Usually 20–30 years
of age

A

Common variable immunodeficiency

32
Q

Deficiency: Reduced IgG1, IgG2, IgG3, or
IgG4

Level of Defect: Defect of Isotype Differentiation

Presentation: Variable with the class and degree of deficiency

A

Isolated IgG subclass deficiency

33
Q

Deficiency: Reduced IgG, IgA, IgE, with
elevated IgM

Level of Defect: B-cell switching

Presentation: Variable

A

CD154 deficiency

34
Q

The blood level of IgG at birth is about the same as the adult level, reflecting transfer of maternal IgG across the placenta.

A

The IgG level declines over the first 6 months of life as maternal antibody is catabolized.

35
Q

Levels of IgA and IgM are very low at birth.

A

The concentrations of all immunoglobulins

gradually rise when the infant begins to produce antibodies at a few months of age in response to environmental stimuli.

36
Q

IgM reaches normal adult levels first, around 1 year of age, followed by IgG at about 5 to 6 years of age.

A
37
Q

In some normal children, IgA levels do not reach normal adult values until adolescence.

A

Therefore, it is important to compare a child’s immunoglobulin levels to age-matched reference ranges.

38
Q

All infants experience low levels of immunoglobulins at approximately
5 to 6 months of age; however, in some babies the low levels persist for a longer time.

A

Because these children do not begin synthesizing immunoglobulins promptly, they can experience severe pyogenic sinopulmonary and skin infections
as protective maternal IgG is cleared.

39
Q

Cell-mediated immunity is normal and there may be normal levels of IgA and IgM.

A

Transient Hypogammaglobulinemia

of Infancy With Normal Numbers of B Cells

40
Q

IgG appears to be the most affected, dropping to at least 2 standard deviations (SDs) below the age-adjusted mean with or without a depression of IgM and IgA

A

Transient Hypogammaglobulinemia

of Infancy With Normal Numbers of B Cells

41
Q

Immunoglobulin levels in infants with this condition usually normalize spontaneously,
often by 9 to 15 months of age

A

Transient Hypogammaglobulinemia

of Infancy With Normal Numbers of B Cells (mechanism not yet known)

42
Q

These patients have normal numbers of circulating CD19+ B cells. This condition
does not appear to be X-linked, although it is more common in males. The cause may be related to a delayed maturation of one or more components of the immune system, possibly Th cells

A

Transient Hypogammaglobulinemia

of Infancy With Normal Numbers of B Cells

43
Q

First described in 1952, is X chromosome linked, so this syndrome affects males
almost exclusively.

A

Bruton’s Tyrosine Kinase (Btk) Deficiency

44
Q

Lack circulating mature CD19+ B cells and exhibit a deficiency or lack of immunoglobulins of all classes. Furthermore, they have no plasma cells in their lymphoid tissues.

A

Bruton’s Tyrosine Kinase (Btk) Deficiency

45
Q

In Bruton’s tyrosine kinase (Btk) deficiency, the patients do, however, have pre-B cells in their bone marrow. Because of the
lack of B cells, _____

A

The tonsils and adenoids are small or entirely absent and lymph nodes lack normal germinal centers

46
Q

T cells are normal in number and function. About half of the patients have a family history of the syndrome.

A

Bruton’s Tyrosine Kinase (Btk) Deficiency

47
Q

They develop recurrent bacterial infections beginning in infancy as maternal antibody is cleared. The patients most commonly develop sinopulmonary infections caused by encapsulated organisms such as streptococci, meningococci, and Haemophilus influenzae.

A

Bruton’s Tyrosine Kinase (Btk) Deficiency

48
Q

Other infections frequently seen in Bruton’s Tyrosine Kinase (Btk) Deficiency

A

Bacterial otitis media, bronchitis, pneumonia,

meningitis, and dermatitis

49
Q

Some patients also have a susceptibility
to certain types of viral infections, including vaccine associated poliomyelitis. In general, live virus vaccines should not be administered to immunodeficient patients

A

Bruton’s Tyrosine Kinase (Btk) Deficiency

50
Q

Results from arrested differentiation

at the pre–B-cell stage, leading to a complete absence of B cells and plasma cells.

A

X-linked hypogammaglobulinemia

51
Q

The underlying genetic mechanism of X-linked hypogammaglobulinemia

A

A deficiency of an enzyme called the Btk in B-cell progenitor cells. Lack of the enzyme apparently causes a failure of immunoglobulin VH gene rearrangement

52
Q

The syndrome can be effectively treated by administration of intramuscular
or intravenous immunoglobulin preparations and vigorous antimicrobial treatment of infections.

A

X-linked hypogammaglobulinemia

53
Q

The syndrome can be differentiated from transient hypogammaglobulinemia
of infancy by _____

A

the absence of CD19+ B cells in the peripheral blood, the abnormal histology of lymphoid tissues, and its persistence beyond 2 years of age.

54
Q

Immunologists have also described patients with a similar clinical presentation to Btk who have a genetic defect that is inherited in an autosomal recessive manner.

A
55
Q

The most common congenital immunodeficiency, occurring in about 1 in 500 persons of American or European descent

A

Selective IgA deficiency

56
Q

Most patients with a deficiency of IgA are asymptomatic. Those with symptoms usually
have infections of the respiratory and gastrointestinal tract and an increased tendency to develop _______

A

Autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid
arthritis (RA), celiac disease, and thyroiditis. Allergic disorders and malignancy are also more common

57
Q

About ___ of the IgA-deficient patients who develop infections also have an IgG2 subclass deficiency. (Selective IgA deficiency)

A

20%

58
Q

If the serum IgA is lower than 5 mg/mL,

A

The deficiency is considered severe

59
Q

If the IgA level is two SDs below the age-adjusted mean but greater than 50 mg/dL,

A

The deficiency is partial

60
Q

Although the genetic defect has not been established, it is hypothesized that lack of
IgA is caused by ____

A

Impaired differentiation of lymphocytes to become IgA-producing plasma cells

61
Q

IgE antibodies specifically directed against IgA are produced by _____ of patients with severe IgA deficiency.

A

30% to 40%

62
Q

IgE antibodies specifically directed against IgA are produced by 30% to 40% of patients with severe IgA deficiency. These antibodies can cause _______

A

Anaphylactic reactions when blood products containing IgA are transfused

63
Q

Most gamma globulin preparations contain significant amounts of IgA. However, replacement IgA therapy is not useful because _____

A

The half-life of IgA is short (around 7 days) and intravenously or intramuscularly administered IgA is not transported
to its normal site of secretion at mucosal surfaces. Furthermore, administration of IgA-containing products can induce the
development of anti-IgA antibodies or provoke anaphylaxis in patients who already have antibodies.

64
Q

A heterogeneous group of disorders with a prevalence of about 1 in 25,000.

A

Common variable immunodeficiency (CVI)

65
Q

Although it has a low incidence (1 in 25, 000), it does make _____ the most common PID with a severe clinical syndrome

A

Common variable immunodeficiency (CVI)

66
Q

Patients usually begin to have symptoms in their 20s and 30s, but age at onset ranges from 7 to 71 years of age. The disorder can be congenital or acquired, or familial or sporadic, and it occurs with equal frequency in men and women.

A

Common variable immunodeficiency (CVI)

Immunology (3 decks)

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