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7. Endocrinology (Medical Knowledge)a > Immunology of Endocrine Disorders > Flashcards

Immunology of Endocrine Disorders Flashcards

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USMLE® Step 1 flashcards
1
Q

What is autoimmunity?

A

An immune response against self-antigens

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2
Q

What are antigens?

A

Structures bound to cell surface of antibodies

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3
Q

What is autoimmune disease?

A

Tissue damage or disturbed function due to an autoimmune response

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4
Q

What is organ specific autoimmune disease?

A

Restricted to single organ, usually an endocrine gland

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5
Q

What is non-organ specific autoimmune disease?

A

Invovle autoantigens widely distributed throughout the body

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6
Q

What is an autoantigen?

A

Normal protein or complex of proteins (and sometimes DNA or RNA) that is recognized by the immune system of patients suffering from a specific autoimmune disease

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7
Q

Are most autoimmune diseases more common in males or females?

A

Females

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8
Q

When does autoimmunity occur?

A

When tolerance to self-antigens breaks down

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9
Q

What is immunological tolerance?

A

Unresponsiveness to an antigen that is induced by previous exposure to that antigen

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10
Q

Explain what happens when a lymphocyte encounters an antigen?

A
  • when lymphocytes encounter antigens they are activated leading to immune responses, or inactivated (or eliminated) leading to tolerance
  • the same antigen may induce an immune response or tolerance, depending on the conditions of exposure and the presence or absence of other stimuli
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11
Q

What are tolerogens?

A

Antigens that induce tolerance

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12
Q

What is self-tolerance?

A

Tolerance to self-antigens

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13
Q

What does failure of self-tolerance result in?

A

immune reaction against self-antigens (autoimmunity) = autoimmune diseases

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14
Q

The immune system can generate a diversity of T-cell antigen receptors and immunoglobulin molecules by different genetic recombination, what does this produce?

A

Many antigen-specific receptors capable of binding to self-molcules

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15
Q

Immune system can generate a diversity of T-cell antigen receptors and immunoglobulin molecules, how is autoimmune disease avoided?

A
  • T and B cells bearing those self-reactive molecules must be either eliminated or downregulated so that immune system is made tolerant to self-antigens
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16
Q

What are the different type of tolerance?

A

Central and peripheral tolerance

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17
Q

What happens in central tolerance?

A

Induced in immature self-reactive lymphocytes in the generative lymphoid organs:

  • thymus plays important role in eliminating T cells with high affinity for self-antigens
  • bone marrow is important in B cell tolerance
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18
Q

For central tolerance, what organ plays an important role in eliminating T cells with high affinity to self-antigens?

A

Thymus

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19
Q

In central tolerance, what organ plays an important role in B cells tolerance?

A

Bone marrow

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20
Q

What is central tolerance also known as?

A

Negative selection

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21
Q

What is central tolerance?

A

Process of eliminating any developing T or B cells that are reactive to self-antigens

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22
Q

Does central tolerance deal with mature or immature lymphocytes?

A

Immature

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23
Q

Does peripheral tolerance deal with mature or immature lymphocytes?

A

Mature

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24
Q

What is peripheral tolerance?

A

Mature lymphocytes that recognise self-antigens in peripheral tissues become incapable of activation by re-exposure to that antigens or die by apoptosis

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25
Q

Explain how peripheral tolerance works?

A
  • An important mechanism for the induction of peripheral tolerance is antigen recognise without co-stimulation or “second signals”
  • Also maintained by regulatory T cells (Tregs) that actively suppress activation of lymphocytes specific for self and other antigens
  • Some self-antigens are sequestered from immune system, and other antigens are ignored
    • Antigens may be sequestered from immune system by anatomic barriers, such as in testes and eyes, and this cannot engage antigen receptors
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26
Q

What are some organs where antigens may be sequestered from the immune system?

A

By anatomical barriers in testes and eyes so cannot engage antigen receptors

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27
Q

What are some mechanisms of peripheral tolerance?

A
  • Anergy (functional unresponsiveness)
  • Treg suppression
  • Deletion (cell death)
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28
Q

What is anergy in peripheral tolerance?

A

Functional unresponsiveness

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29
Q

What is deletion in peripheral tolerance?

A

Cell death (apoptosis)

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30
Q

What cell is responsible for performing peripheral tolerance?

A

Dendritic cell

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31
Q

What happens in central tolerance?

A
  • Immature lymphocytes specific for self antigens may encounter these antigens in generative (central) lymphoid organs and are
    • Deleted, change their specificity (B cells only) or develop into regulatory lymphocytes called Tregs (only CD4+ T cells can do this)
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32
Q

What happens in peripheral tolerance?

A
  • Some self-reactive lymphocytes may mature and enter peripheral tissues and may be inactivated or deleted by encounter with self-antigens in these tissues or are suppressed by regulatory T cells (Tregs)
  • Note that T cells recognise antigens presented by antigen-presenting cells (APCs)
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33
Q

In central tolerance, what are the only cells that can develop into regulatory lymphocytes called Tregs?

A

Helper T cells (CD4+ T cells)

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34
Q

What are helper T cells also known as?

A

CD4+ T cells

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35
Q

What are cytotoxic T cells also known as?

A

CD8+ T cells

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36
Q

In central tolerance, what are the only cells that can have their specificity changed?

A

B cells

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37
Q

How can peripheral tolerance be overcome?

A
  • Inappropriate access of self-antigens
  • Inappropriate or increased local expression of co-stimulatory molecules
  • Alternations in the ways in which self-molecules are presented to the immune system
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38
Q

When is peripheral tolerance more likely to be overcome?

A

When inflammation or tissue damage is present due to increased activity of proteolytic enzymes which can cause intra and extra-cellular proteins to be broken down

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39
Q

Why is peripheral tolerance more likely to be overcome when inflammation or tissue damage is present?

A

Increased activity of proteolytic enzymes causes intra and extra-cellular proteins to be broken down:

  • leading to high concentrations of peptides being presented to responsive T cells
  • structures of self-peptides may be altered by viruses, free radicals or ionising radiation thus bypassing previously established tolerance
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40
Q

Almost all types of autoimmune disease are more prevalent in woman, what is an example of one that is more prevalent in en?

A

Ankylosing spondylitis

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41
Q

What are the 2 types of autoimmune disease?

A

Non-organ specific autoimmune disease

Organ-specific autoimmune disease

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42
Q

How does non-organ and organ specific autoimmune disease differ?

A

Non-organ specific affects multiple organs, being associated with autoimmune responses against self-molecules that are widely distributed throughout the body

Organ specific is restricted to one organ, which is usually an endocrine gland

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43
Q

What molecules does non-organ specific autoimmune disease affect?

A

Intracellular molecules involved in transcription and translation

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44
Q

What are some genetic factors of autoimmune disease?

A

Clusters within familes

Alleles of MHC (major histocompatibility complex)

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45
Q

What is the major histocompatible complex (MHC)?

A

Set of genes that code for cell surface proteins essential for the acquired immune system to recognize foreign molecules in vertebrates, which in turn determines histocompatibility

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46
Q

What are some environmental factors of autoimmune disease?

A
  • Infections
    • Molecular mimicry
    • Upregulation of co-stimulation
    • Antigen breakdown and presentation changes
  • Drugs
    • Molecule mimicry
    • Genetic variation in drug metabolism
  • UV radiation
    • Trigger for skin inflammation
    • Modification of self-antigen
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47
Q

How does infection cause autoimmune disease?

A
  • Molecular mimicry
  • Upregulation of co-stimulation
  • Antigen breakdown and presentation changes
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48
Q

How do drugs cause autoimmune disease?

A
  • Molecule mimicry
  • Genetic variation in drug metabolism
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49
Q

How does UV radiation cause autoimmune disease?

A
  • Trigger for skin inflammation
  • Modification of self-antigen
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50
Q

What is molecular mimicry?

A

Possibility that sequence similarities between foreign and self-peptides are sufficient to result in the cross-activation of autoreactive T or B cells by pathogen-derived peptides

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51
Q

What is co-stimulation?

A

Secondary signal which immune cells rely on to activate an immune response in the presence of an antigen-presenting cell. In the case of T cells, two stimuli are required to fully activate their immune response.

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52
Q

What does DC stand for?

A

Dendritic cell

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53
Q

Describe the role of infection in development of autoimmunity?

A

Microbes may activate the APC to express co-stimulators, and when these APCs present self-antigens the self reative T cells are activated rather than rendering tolerance

or some microbial antigens may cross-ract with self antigens (molecular mimicry), initiating an immune response that may activate T cells specific for self antigens

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54
Q

What are some examples of microbial antigens that can cause molecular mimicry?

A
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55
Q

Explain the genetic susceptibility to autoimmunity?

A
56
Q

What does APC stand for?

A

Antigen presenting cell

57
Q

What are some general treatments of autoimmune disease?

A
  • Suppression of the damaging immune response
    • Before irreversible tissue damage
    • Early detection is the challenge
    • Problem with specificity of treatments and toxicity
  • Replacement of the function of the damaged organ
    • Used for hypothyroidism and insulin dependent diabetes mellitus
58
Q

What is diabetes?

A

Abnormal metabolic state characterised by glucose intolerance due to inadequate insulin access

59
Q

What are the 2 main types of diabetes?

A

Type 1 diabetes

Type 2 diabetes

60
Q

Does T1 and T2 diabetes have a juvenile onset or a mature onset?

A

T1 - juvenile

T2 - mature

61
Q

What pathology causes T1 diabetes?

A

Destruction of beta cells (probably due to viral infection and genetic factors)

62
Q

What pathology causes T2 diabetes?

A

Defective insulin access

63
Q

What are some examples of complications of diabetes?

A

Accelerated atherosclerosis

Susceptability to infection

Microangiopathy affecting many organs

64
Q

What part of the pancreas forms the endocrine pancreas?

A

Islet of Langerhans

65
Q

What percentage of the total pancreas mass is composed of the endocrine pancreas (Islet of Langerhans)?

A

1%

66
Q

What are the 4 cell types present in Islet of Langerhans?

A
67
Q

What cell type is most prevalent in Islet of Langerhans?

A

Beta cells

68
Q

What do beta cells secrete?

A

Insulin

69
Q

What do alpha cells secrete?

A

Glucagon

70
Q

What do delta cells secrete?

A

Somatostatin

71
Q

What do pancreatic polypeptide cells secrete?

A

Pancreatic polypeptide

72
Q

What are the actions of insulin?

A
73
Q

What are the actions of glucagon?

A
74
Q

What are the actions of somatostatin?

A
75
Q

What is the function of pancreatic polypeptide?

A
76
Q

Is the prevalence of diabetes increasing or decreasing?

A

Increasing

77
Q

What is type 1 diabetes also known as?

A

Insulin dependent diabetes

78
Q

What is type 2 diabetes also known as?

A

Insulin independent diabetes

79
Q

Explain the aetiology of T1 diabetes?

A

Autoimmune destruction:

  • Circulatory antibodies to islet cells
  • Patients prone to develop other organ specific autoimmune diseases

Genetic factors:

  • Association with certain HLA types
  • Environmental factors play a role to

Viral infection:

  • Antibodies to certain viruses are high in patients
  • Viruses may act as triggers for autoimmune destruction
    • Coxsackie B
    • Mumps
80
Q

What genetic factors impact the aetiology of T1 diabetes?

A

Association with certain HLA types

81
Q

What viruses may trigger T1 diabetes?

A

Coxsackie B

Mumps

82
Q

What are some complications of T1 diabetes?

A
83
Q

What does the thyroid gland synthesis?

A

T3 and T4

84
Q

What is the production of T3 and T4 under the negative feedback off?

A

TSH (from anterior pituitary)

85
Q

What are some examples of thyroid diseases?

A
  • Secretory malfunction
    • Hyperthyroidism
    • Hypothyroidism
  • Swelling of the entire gland
    • Goitre
  • Solitary masses
    • Nodular goitre
    • Adenoma
    • Carcinoma
86
Q

What do C-cells in the thyroid gland secrete?

A

Calcitonin

87
Q

What are the follicles of the thyroid gland lined by?

A

Cuboidal cells

88
Q

In terms of T3, T4 and TSH, what is hyperthyroidism due to?

A

Excess T3 and T4, very rarely due to excess TSH

89
Q

What is the most common cause of hyperthyroidism?

A

Grave’s disease

Could also be due to functioning adneoma, but not as likely

90
Q

What can cause hyperthyroidism?

A
  • Graves thyroiditis
  • Functioning adenoma
  • Toxic nodular goitre
  • Exogenous thyroid hormone (rare)
  • Ectopic secretion by ectopic thyroid tissue or tumours
91
Q

What are the signs and symptoms of hyperthyroidism?

A
92
Q

What is the most common cause of thyrotoxicosis?

A

Grave’s thyroiditis

93
Q

What is grave’s thyroiditis usually associated with?

A

Diffuse goitre

94
Q

What are 2 kinds of goitre?

A

Diffuse goitre

Nodular goitre

95
Q

What is diffuse goitre?

A

Entire thyroid gland swells up and is smooth to touch

96
Q

What is nodular goitre?

A

Lumps called nodules develop in the thyroid

97
Q

Histologically, what is observed in Grave’s thyroiditis?

A
  • Hyperplasia of the acinar epithelium
  • Reduction of stored colloid
  • Local accumulation of lymphocytes with lymphoid follicle formation
98
Q

Explain the pathogenesis of Grave’s thyroiditis being an organ specific autoimmune disease?

A
  • Autoantibody (IgG) (LATS) which binds to the thyroid epithelial cells and mimics the action of TSH
  • LATS stimulates the function and growth of thyroid follicular epithelium
  • Exophthalmos, pretibial myxoedema (accumulation of mucopolysaccharides in the deep dermis of skin) and finger clubbing
99
Q

What autoantibody is responsibly for Grave’s thyroiditis?

A

Long acting thyroid stimulating immunoglobin (LATS)

100
Q

What is the most common cause of hypothyroidism?

A

Hashimoto thyroiditis which is an autoimmune disorder

101
Q

What is a congenital cause of hypothyroidism?

A

Cretinism

102
Q

What is the clinical presentation of hypothyroidism?

A
103
Q

What is cretinism?

A

When hypothyroidism is present in new-born, physical growth and mental development is impaired, sometimes irreversibly

104
Q

What is the cause of cretinism when its endemic in areas and when it is sporadic?

A

Endemic - insufficient iodine for thyroid hormone synthesis

Sporadic - congenital absence of thyroid tissue, or to enzyme defects blocking hormone synthesis

105
Q

What does Hashimoto’s thyroiditis cause?

A

May initially cause thyroid enlargement, but later there may be atrophy and fibrosis

Cause hypothyroidism (most common cause)

106
Q

What can happen in the early stages of Hashimoto’s thyroiditis that contradicts it causing hypothyroidism?

A

Damage to thyroid follicles may lead to release of thyroglobulin causing a transient phase of thyrotoxicosis

107
Q

Explain the histology of Hashimoto’s thyroiditis?

A
  • Densely infiltration by lymphocytes and plasma cells, with lymphoid follicle formation
  • Colloid content is reduced
  • Thyroid epithelial cells show a characteristic change in which they enlarge and develop eosinophilic granular cytoplasm due to proliferation of mitochondira (termed Askanazy cells, Hurthle cells or oncocytes)
  • In advanced cases, may be fibrosis
108
Q

Is Hashimoto’s thyroiditis an organ specific or non-organ specific autoimmune disease?

A

Organ specific autoimmune disease

109
Q

What are the two antibodies that can be detected in the serum of most patients with Hashimoto’s thyroiditis?

A

One reacting with thyroid peroxidase

Other reacting with thyroglobulin

110
Q

What is the genetic link to Hashimoto’s thyroiditis?

A

HLA genes

111
Q

Does Hashimoto’s thyroiditis affect more males or females?

A

Females

112
Q

What are autoimmune polyendocrine syndromes?

A

Diverse group of conditions characterised by functional impairment of multiple endocrine glands due to loss of immune tolerance

113
Q

What are examples of conditions frequently included in autoimmune polyendocrine syndromes?

A

Alopecia

Celiac disease

Autoimmune gastritis with vitamin B12 deficiency that affects nonendocrine organs

114
Q

What is the pathophysiology of autoimmune polyendocrine syndromes?

A
  • Circulating autoantibodies and lymphocytic infiltration of the affected tissues or organs
  • Eventually leading to organ failure
115
Q

How do the components of autonomic polyendocrine syndrome change throughout life?

A

Can occur in patients from early infancy to old age

New components to a syndrome can appear throughout life

116
Q

What is the aetiology of autoimmune polyendocrine syndromes?

A

Combination of genetic susceptibility and environmental factors

117
Q

What are the different autoimmune polyendocrine syndromes?

A

APS-1

APS-2

IPEX

118
Q

What does APS stand for?

A

Autoimmune polyendocrine syndrome

119
Q
A
120
Q

What is APS-1 also known as?

A

Autoimmune polyendocrinopathy-candidiasis

121
Q

What is APS-1?

A

Rare autosomal recessive disease caused by mutations in the autoimmune regulatory gene (AIRE)

122
Q

What is the estimated prevalence of APS-1?

A

1:100000

123
Q

What are the clinical features of APS-1?

A
  • At least 2 of 3 cardinal components during childhood
    • Chronic mucocutaneous candidiasis
    • Hypoparathyroidism
    • Primary adrenal insufficiency (Addison’s disease)
  • Other typical components
    • Enamel hypoplasia
    • Enteropathy with chronic diarrhoea or constipation
    • Primary ovarian insufficiency
  • Less frequent components
    • Bilateral keratitis
    • Periodic fever with rash
    • Autoimmunity induced hepatitis, pneumonitis, nephritis, exocrine pancreatitis and functional asplenia
  • Rare findings
    • Retinitis
    • Metaphyseal dysplasia
    • Pure red cell aplasia
    • Plyarthritis
124
Q

APS-1 must have at least 2 of what 3 components during childhood?

A
  • Chronic mucocutaneous candidiasis
  • Hypoparathyroidism
  • Primary adrenal insufficiency (Addison’s disease)
125
Q

Is APS1 or APS2 more common?

A

APS-2

126
Q

APS-2 is characterised by 2 of what 3 components?

A
  • Type 1 diabetes
  • Autoimmune thyroid disease
  • Addison’s disease
127
Q

Is APS-2 more common in men or woman?

A

Woman

128
Q

APS-2 is characterised by at least 2 of type 1 diabetes, autoimmune thyroid disease and Addison’s disease. What are some other autoimmune conditions that can develop?

A
  • Celiac disease
  • Alopecia, vitiligo
  • Primary ovarian insufficiency
  • Pernicious anaemia
129
Q

When does the onset of APS-2 usually occur?

A

Young adulthood, later than APS-1

130
Q

Which of APS1 and APS2 usually has the later onset?

A

APS-2, which occurs in early adulthood

131
Q

What does IPEX stand for?

A

X-linked immunodysregulation, polyendocrinopathy and enteropathy

132
Q

What is IPEX characterised by?

A
  • Early onset type 1 diabetes
  • Autoimmune enteropathy with intractable diarrhoea and malabsorption
  • Dermatitis that may be eczematiform, icthyosiform or psoriasiform
133
Q

What are the different manifestations of dermatitis in IPEX?

A

Eczematiform, icthyosiform or psoriasiform

134
Q

What in the blood is frequently elevated in IPEX?

A

Eosinophils and IgE levels

135
Q

What are some later manifestations of IPEX?

A
  • Autoimmune thyroid disease
  • Alopecia
  • Various autoimmune cytopenias
  • Hepatitis
  • Exocrine pancreatitis
136
Q

What is the treatment of IPEX?

A

If often fatal in first few years unless treated with immunosuppresive agent or if possible, with allogeneic bone marrow transplantation which can cure the disease

7. Endocrinology (Medical Knowledge)a (28 decks)

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