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HHAD: Human Disease > Immunodeficiency and HIV > Flashcards

Immunodeficiency and HIV Flashcards

1
Q

Name the 4 main components of the immune system

A
  • T cells
  • B cells
  • Phagocytes
  • Complement
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2
Q

What may indicate immunodeficiency?

A

Occurrence of repeated or unusual infections

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3
Q

What is the definition of immunodeficiency?

A

A disease that is the result of loss of function (or a defective function) of a component of the immune system. It can be due to the absence of that component

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4
Q

What are the 2 types of immunodeficiency?

A

primary

secondary

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5
Q

What is primary immunodeficiency?

A

Genetically determined or result of developmental anomalies.
Inherent (permanent)
Congenital.
Rare.

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6
Q

What is secondary immunodeficiency?

A

Acquired.
Caused by disease or immunosuppressive treatment (extrinsic factors).
More common

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7
Q

Which type of immunodeficiency is more common?

A

Secondary

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8
Q

Describe the genetic primary immunodeficiencies (3)

A
  • Autosomal (non-sex chromosome)
  • X-linked (sex chromosome)
  • Gene deletions/rearrangements/polymorphisms
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9
Q

Outline the biochemical or metabolic primary immunodeficiency conditions and what immune cells are involved in each (3)

A
  1. Adenosine deaminase deficiency (T cell)
  2. Purine nucleoside phosphorylase deficiency (T cell)
  3. Arrest in development (B cells, T cells, Phagocytes)
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10
Q

Complement deficiencies:

Outline the consequences/disease/infections of a defect in the classical pathway (C1qrs, C2 or C4) (2)

A
  1. Unable to remove Ag-Ab complexes (type 3 hypersensitivity): Immune complex disease
  2. Susceptible to encapsulated organisms (Strep pneumoniae, Neisseria spp)
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11
Q

Complement deficiencies:

Outline the consequences/disease/infections of a C3 deficiency (3)

A
  1. Opsonisation of microbes is defective
  2. Removal by phagocytosis is compromised
  3. Susceptibility to encapsulated organisms (e.g. strep, Neisseria, pyogenic organisms)
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12
Q

Complement deficiencies:
Outline the consequences/disease/infections of a defect in the alternative pathway (Factor B, Factor D and Properdin) (3)

A
  1. Low C3b levels
  2. No immune complex disease
  3. Pneumococcal and meningococcal infections
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13
Q

Complement deficiencies:

Outline the consequences/disease/infections of a defect in the MAC complex (3)

A
  1. Inability to lyse bacterial cells
  2. Recurrent infection with Neisseria meningitidis
  3. Humoral (antibody) immunity is unaffected
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14
Q

Name 3 types of bacteria that a person may have an increased susceptibility to if they had a complement deficiency

A
  1. Pneumococcus
  2. Streptococcus
  3. Neisseria
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15
Q

Phagocytosis deficiency: What are the consequences of stem cell differentiation deficiency? (2)

A
  • Neutropenia
  • Leukocyte adhesion disease (lack of adhesion molecules (CD18 on Neutrophil binds ICAM-1 required for Neutrophil recruitment)
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16
Q

Phagocytosis deficiency: what are the consequences of a phagocytosis deficiency (Chediak- Higashi syndrome)? (3)

A
  • Lack of fusion of phagosome with lysosomes
  • Defect in lysosomal trafficking regulator
  • Staph aureus susceptibility
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17
Q

Phagocytosis deficiencies: What are the consequences of Defective intracellular killing (chronic granulomatous disease)? (3)

A
  • Defect in NADPH system: required for free radical formation (ROS)
  • Lack of oxygen dependent killing
  • Increased bacterial and fungal infections
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18
Q

If a person has a phagocytosis deficiency - what infections are they more susceptible to, and what is the treatment for this deficiency?

A
  1. Increased susceptibility to bacterial and fungal infections of skin and mucosal tissues
  2. Treatment with antibiotics or bone marrow transplant
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19
Q

Congenital abnormalities in phagocytosis deficiencies results in what? (3)

A

Differentiation, chemoattraction and intracellular killing

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20
Q

Phagocytosis deficiencies: what do secondary extrinsic defects result from?

A

Antibody/complement deficiencies i.e. defect in opsonisation which have a subsequent affect on phagocytosis

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21
Q

Humoral/AB (B cell) deficiencies:
what are the consequences if B cells fail to develop (e.g. Bruton’s agammaglobulinaemia)? (2)

Which age demographic and gender is this most common in?

A
  • Few or no mature B cells/antibodies (Blockage in maturation of pre-B cells to B cells)
  • T cells are normal
  • Common in male infants; protected for 6 months; then recurrent bacterial infections
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22
Q

Humoral/AB (B cell) deficiencies:
what are the consequences of Common Variable Immunodeficiency (CVID)?

What age demographic/age does this more commonly affect?

Which antibodies are people deficient in? (2)

A
  1. Either B cells do not undergo terminal differentiation (no IgG/IgA) or T cell signalling is defective
  2. Both sexes, adults (late onset 15-35 years)
  3. IgG/IgA
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23
Q

Humoral/AB (B cell) deficiencies:

what are the consequences of hyper IgM syndrome?

A
  • B cells do not switch antibody classes from IgM
  • Increased IgM but little or no IgG in circulation
  • Lack of IgG antibody opsonisation/phagocytosis (e.g. defective CD40 on B cells or CD40L on T cells)
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24
Q

Humoral/AB (B cell) deficiencies:
What bacterial infections would these patients be more susceptible to? (3)

What’s the treatment for these deficiencies?

A
  1. Mainly encapsulated bacteria: recurrent extracellular bacterial infections (Pneumococcus, strep, haemophilus)
  2. Life-long or periodic gamma globulin injections.
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25
Q

Which particular defects alone are very rare?

A

Cellular immunity alone

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26
Q

What do most T cell deficiencies also result in?

A

Humoral defects - because T cells help B cells develop and stimulate antibody production

27
Q

Cellular (T cell) deficiencies:

What are the consequences of lack of a developed thymus (DiGeorge’s syndrome)? (3)

A

Lack of T cells (susceptible to many infections) - abnormal B cell immunity.

Hypoparathyroidism - resulting in hypocalcaemia

Congenital heart disease

28
Q

Cellular (T cell) deficiencies:

What are the consequences of stem cell defects or death of developing T cell? (3)

A

SCID (severe combined deficiency syndrome)
1. 50% have defect in a gamma chain used by cytokine receptors (IL-2/4/7/9/15/21)

  1. 25% have adenosine deaminase deficiency or purine nucleoside phosphorylase deficiency (adenine/guanine)
  2. Metabolite build up, thus inhibiting DNA synthesis
29
Q

Cellular (T cell) deficiencies:

What are the consequences of MHC II deficiency? (3)

A
  1. No mature CD4+ T cells
    - APC function low, reduced B/T cell activation, no Ab
    - Death by 5 years due to bacterial and viral infections
29
Q

Cellular (T cell) deficiencies:

What are the consequences of MHC II deficiency? (3)

A
  1. No mature CD4+ T cells
    - APC function low, reduced B/T cell activation, no Ab
    - Death by 5 years due to bacterial and viral infections
30
Q

Cellular (T cell) deficiencies:

What is the treatment for these conditions?

A

Bone marrow transplant (gene therapy)

31
Q

Cellular (T cell) deficiencies:

What is it that makes these often fatal in early years of life?

A

Opportunistic infections (viruses, fungi, parasites, intracellular bacteria)

32
Q

What are the clinical features of immunodeficiency? (10)

A
  • Chronic infection
  • Recurrent infection
  • Unusual microbial agents
  • Incomplete response to treatment
  • Skin lesion- candidiasis, warts
  • Diarrhoea
  • Recurrent abscesses
  • Recurrent osteomyelitis
  • Autoimmunity
  • Failure to thrive
33
Q

Give examples of secondary/acquired/environmental immunodeficiency (6)

A
  1. Therapeutic drugs (chemo, post-transplant immunosuppression, radiation)
  2. Infection (e.g. HIV, post-viral)
  3. Metabolic disorders
  4. Chronic/other infection (diabetes)
  5. Malnutrition, aging
  6. Burns/trauma - loss of immunoglobulin via damaged skin
34
Q

What is the causative agents of AIDS?

A

HIV - Human Immunodeficiency Virus

35
Q

How many genes does HIV contain? Can you name them?

A
  1. (written in alphabetical order):
  2. env: Envelope
  3. gag: Group-specific antigen
  4. nef: Negative-regulation factor
  5. pol: Polymerase
  6. rev: Regulator of viral expression
  7. tat: Transactivator
  8. vif: Viral Infectivity
  9. vpr: Viral protein R
  10. vpu: Viral protein U
36
Q

What is the gene product/function of the HIV gene: gag? (2)

A

Core proteins

Matrix proteins

37
Q

What is the gene product/function of the HIV gene: pol? (3)

A

Reverse transcriptase
Protease
Integrase enzymes

38
Q

What is the gene product/function of the HIV gene: env? (3)

A

Transmembrane glycoproteins
gp120 binds CD4 and CCR5
gp41 is required for virus fusion and internalisation

39
Q

What is the gene product/function of the HIV gene: tat? (1)

A

Positive regulator of transcription

40
Q

What is the gene product/function of the HIV gene: rev? (1)

A

Allows export of unspliced and partly spliced transcripts from nucleus

41
Q

What is the gene product/function of the HIV gene: vif? (1)

A

affects particle infectivity

42
Q

What is the gene product/function of the HIV gene: vpr? (3)

A

Transport DNA to nucleus
Augments virion production
Cell cycle arrest

43
Q

What is the gene product/function of the HIV gene: vpu? (2)

A

Promotes intracellular degradation of CD4

Enhances release of virus from cell membrane

44
Q

What is the gene product/function of the HIV gene: nef? (2)

A 
Augments viral replication in vivo and in vitro
Decreases CD4, MHC class I & II expression
45
Q

What is the first step in HIV infection?

A

Sequestration/capture by epithelial cells.
HIV can interact directly with epithelial cells.
They do this via surface molecule gp120 that interact with molecules on the epithelial cell surface.

46
Q

Name receptors that allow gp120 of HIV to interact with epithelial cells during an HIV infection (3)

Name 2 coreceptors that can be involved

A
  1. Heparan Sulphate Proteoglycans (HSPGs) e.g. Syndecans
  2. Galactosylceramide (GalCer)
  3. DC-SIGN
  4. CD4

Co receptors: CCR5, CXCR4

47
Q

How is HIV captured by dendritic cells, Langerhans cell?

A

Dendritic cells molecules are bound by gp120 (env)

By the same receptors mentioned before: Heparan Sulphate Proteoglycans HSPGs, Galactosylceramide GalCer

48
Q

What are the key receptors that transfer the virus from dendritic cells to T helper cells/macrophages?

  • 1 main receptor
  • 2 co-receptors
A

T cell/macrophage molecules bound by gp120 (Env)
Main receptor: CD4

Coreceptors:
CCR5 (macrophage- R5 tropic virus)
CXCR4 (T helper cell - X4 tropic virus)

49
Q

Which co-receptor is involved when HIV is transferred from the dendritic cells to macrophages?

A

CCR5 (R5 tropic virus)

50
Q

Which co-receptor is involved when HIV is transferred from the dendritic cells to T helper cells?

A

CXCR4 (X4 tropic virus)

51
Q

Outline the process of HIV infection (8)

A
  1. Virus particle binds to CD4 and co-receptor on T cell
  2. Viral envelope fuses with cell membrane allowing viral genome to enter the cell
  3. Reverse transcriptase copies viral RNA genome into double-stranded cDNA
  4. Viral cDNA enters nucleus and is integrated into host DNA
  5. T cell activation induces low level transcription of provirus
  6. RNA transcripts are are multiply spliced, allowing translation of early genes tat and rev
  7. Tat amplifies transcription of viral RNA. Rev increases transport of singly spliced or unspliced viral RNA to cytoplasm.
  8. The late proteins (Gag, Pol, Env) are translated and assembled into virus particules which bud from the cell
52
Q

Which type of cells never really recover once they have depleted as a result of an HIV infection?

A

Mucosal CD4+ T cells

53
Q

What happens to the levels of cells during the course of HIV infection during the final period (AIDS)? (4)

A
  1. Immune activation starts to slightly drop towards the end of this period (after it was steadily rising)
  2. Circulating CD4+ T cells rapidly deplete
  3. Viremia increases
  4. Mucosal CD4+ T cells remain depleted
54
Q

What happens to the levels of cells during the course of HIV infection during the acute phase? (4)

A
  1. Viremia drastically increases
  2. Immune activation increases
  3. Circulating CD4+ T cells drops but then increases again towards the end of this phase
  4. Mucosal CD4+ T cells drastically deplete
55
Q

What happens to the levels of cells during the course of HIV infection during the chronic phase? (4)

A
  1. Viremia fluctuates up and down
  2. Immune activation continues to increase
  3. Circulating CD4+ T cells steadily decline
  4. Mucosal CD4+ T cells stay depleted
56
Q

What are the main symptoms of acute HIV infection?

A 
> Fever
> Weight loss
> Malaise
> Headache
> Neuropathy
> Mouth sores
> Mouth thrush
> oesophageal (throat) sores
> Myalgia
> Liver and spleen enlargement
> Lymphadenopathy
> Skin rash
> Nausea
> Vomiting
57
Q

What is the main consequence of HIV infection?

A

As CD4+ T helper cell numbers are lowered, this leads to increased opportunistic infections

58
Q

Name a parasite that may be an opportunistic infection as a consequence of HIV infection? (4)

A

Toxoplasma spp.
Cryptosporidium spp.
Leishmania spp.
Microsporidium spp.

59
Q

Name an intracellular bacteria that may be an opportunistic infection as a consequence of HIV infection? (3)

A

Mycobacterium tuberculosis
Mycobacterium avium intracellulare
Salmonella spp.

60
Q

Name a parasite that may be an opportunistic infection as a consequence of HIV infection? (5)

A 
Pneumocystis carinii
Cryptococcus neoformans
Candida spp. 
Histoplasma capsulatum
Coccidioides immitis
61
Q

Name a virus that may be an opportunistic infection as a consequence of HIV infection? (3)

A

Herpes simplex virus
Cytomegalovirus
Varicella zoster

62
Q

Name a malignancy that may be a consequence of HIV infection? (3)

A

Kaposi’s sarcoma (HHV8)
Non-Hodgkin’s lymphoma (Incl. EBV+ Burkitt’s lymphoma)
Primary lymphoma of the brain.

HHAD: Human Disease (20 decks)

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