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DEN303 - IHD > Immunodeficiency > Flashcards

Immunodeficiency Flashcards

The difference between primary and secondary immunodeficiencies Examples of Primary Immunodeficiency Examples of Secondary Immunodeficiency

1
Q

Primary immunodeficiency

What does it affect

A

Intrinsic genetic defects in immune system

T&B cells (Ab production), complement cascade, phagocytes

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2
Q

Secondary immunodeficiency

Caused by?

A

External factors which can deleteriously affect the immune system

Drugs, malnutrition, viral infection

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3
Q

Primary immunodeficiency (Detail)

What does it cause

Two types

A

Absence or failure of normal fx in one or more elements of immune system

Increased susceptibility to infection

Specific/Non-specific

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4
Q

Specific immunodeficiency

A

Abnormalities of T or B cells - adaptive immune system

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5
Q

Non-specific immunodeficiency

A

Abnormalities of phagocytes or complement - innate immune system

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6
Q

Two categories of primary ID and what are they at risk of

A
  1. defects in Ig, Completment, phagocytes –> recurrent bacterial infections
    PYOGENIC
  2. defects in cell-mediated immunity (T cells)
    Infection by commensal organisms
    OPPORTUNISTIC infections
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7
Q

B cell deficiencies

Increase in

A

Defects in B cell fx

Pyogenic infections

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8
Q

X-linked Agammaglobulinaemia

Which gene is affected therefore who does it affect

Signs and symptoms

A

First ID discovered

Gene on X-chromosome
Affects males

No B-cells
No tonsils
Little IgG in serum (other Igs present)

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9
Q

X-linked recessive inheritance

Occurs more frequently in

Females having one copy of gene =

A

Males because only one X chromosome

Carriers
Passed on to ill sons and carrier daughters
Ill males pass on to daughters

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10
Q

X linked dominant inheritance

Mechanism

Who has mutated gene

Stats

Affected man?

A

Less common

Dominant gene carried on X chromosome and only one copy needed to cause disorder
Mother passes on mutated genes to offspring

50% of children will have disease

Sons will not be affected if father has gene but daughters will

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11
Q

X linked agammaglobulinaemia

Mechanism

Results in

Symptoms

Therapy

A

Defective btk gene which encodes B cell tyrosine kinase
Important in B cell maturation
No B cell maturation so no IgG - poor Ab responses

Protective maternal IgG during first 6-12 months of life
Recurrent pyogenic infections - repeated injections of gamma globulin

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12
Q

Hyper-IgM Immunodeficiency

What kind of condition

Susceptible to…because

A

Deficient in IgG and IgA but HYPER IgM
X linked recessive condition with CD40 mutations
IgM turns to IgG

Susceptible to pyogenic infections and autoimmune disease due to anti IgM antibodies to neutrophils and platelets

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13
Q

IgA deficiency

Mechanisms

A

Most common
Failure in terminal diff of B cells to plasma cells

Type III hypersensitivity develops

Susceptible to pyogenic infections

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14
Q

T cell deficiencies result in

A

Opportunistic infections

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15
Q

Severe combined immunodeficiency

Results in

Example

A

SCID
Individuals with no or poor T cell fx

B cell function depends on T cell fx
T cell deficient individuals have poor humoral fx due to poor interaction

Commensal organism infections e.g oral candidiasis

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16
Q

Signs and symptoms of SCID

A 
Few lymphocytes
More common in males 
50% cases X-linked 
Incompatible with life - infants die within first two years of life without bone marrow transplantation 
Sibling or parental
17
Q

DiGeorge syndrome

Distinctive facial features

A

Affected thymus in foetal development –> T cell deficiency

Wide spread eyes, low set ears, upper lip shortened,abnormal aorta with CVS disease

18
Q

MHC II Deficiency

A

Failure to express MHC II antigens on antigen presenting cells
Positive selection of CD4 cells in thymus doesn’t occur
Infants are deficient in CD4 cells therefore

CD4 cell deficiency leads to Ab deficiency

19
Q

Complement deficiency

Most common

A

Deficiencies in C3, Factor H and I
Increased susceptibility to pyogenic infections

MAC deficiencies
Increase in susceptibility to neisseria

Hereditary angioneurotic oedema

20
Q

HAO

A

Hereditary angioneurotic oedema
Complement deficiency
C1 inhibitor
Inhibits C1 activation (first step of cascade)
Inhibits complement cascade and elements of clotting cascade
Severe oedema due to plasma leakage

Recurrent swelling

Intestine - abdo pains and vomiting
URT - choke and death due to obstruction

21
Q

Chronic granulomatous disease
Due to

What is the problem

A

Defective NAPDH oxidase

NADPH Oxidase
NADPH + 2O2 —-> NADP+ + 2 O2 + H+

NADPH oxidase usually catalyses reaction to produce superoxide ions
Superoxide ions are required to kill bacteria after phagocytosis
Bacteria continue to live within phagocytes

Phagocytes cannot form superoxide ions and H2O2 to kill microbes

Organisms remain alive in phagocytes - persistent intracellular infections and granulomas form

Infections with s pneumoniae and abscessed in liver and skin

22
Q

Diagnosis of CGD

A

Inability of phagocytes to reduce nitroblue tetrazolium dye

Usually pale yellow when taken up by phagocytes during phagocytosis
In healthy phagocytes it is reduced by ROS to purple

Remains yellow in CGD patients

23
Q

Leukocyte Adhesion Deficiency

Type 1

ALSO

Type 2

A

LAD

Deficient for CD18
Defective complement receptor 3 (for CD18)
Binds bacteria opsonised with C3bi - increase phagocytosis
Opsonised bacteria cannot be phagocytosed due to defective receptor –> lack of binding –> recurrent infections

Defective CD18
Important in leukocyte adhesion
Phagocytes cannot bind to epithelium and extravasate and enter tissues

Defective receptors CD15 which bind selections
Phagocytes cannot roll on the endothelium

24
Q

Secondary immunodeficiency detailed

Occurs because

Factors

A

Due to external effects on immune system

Drugs (hormones, cancer, therapy, transplants)
Nutrition
Viruses
Burns

25
Q

Drugs (involvement in Secondary ID)

Taken for
Example diseases and explain effect

Repeat dose leads to

A
  1. Corticosteroids - glucocorticoids
    Significant changes in leukocytes in circulation post tx

Lymphocytopenia - T cells affected more than B cells
Monocytopenia - quick in 2hr then returns to normal by 24hrs
Neutrophilia - due to release of mature neutrophils from bone marrow

Low lymphocytes, lack of Ab and defective cytokine synthesis

26
Q

Anti cancer therapy

Effects of radiotherapy

Chemotherapy - examples of meds and effects of

A

Immunosuppression - cell division suppressed

Radiotherapy

  • causes strand breaks in DNA
  • increases apoptosis and stops proliferation
  • targeted at cancer cells but also affects bone marrow and lymphoid tissue
  • stops immune cell production, proliferation and differentiation
  • susceptible to organisms not normally pathogenic –> COMMENSALS e.g candida
  1. CYCLOPHOSPHAMIDE
    - pro drug that is activated inside the body
    - when activated it cross links DNA to stop cell proliferation and increase apoptosis
    - mainly affects lymphocytes (B cells mostly)
    Loss of cell-mediated and Ab production
  2. Azathioprine
    Azathioprine is converted to 6-mercaptopurine in the body then metabolised to thioinosinic acid (a false base - chain terminator)
    Gets incorporated into Dna and stops DNA replication and proliferation
  3. 5-fluorouracil (ADRUCIL)
    - stops development of nucleotides required for DNA replication
    - damage to immune system as it affects T and B and NK cell numbers
27
Q

Cyclosporin in organ transplantation

Mechanism

A

Immunosuppressant drug used to reduce activity of immune system and prevent organ rejection
Affects T cells by affecting IL-2 Production

28
Q

T cell antigen recognition and activation

A

CD28 on T cells binds to CD80 on antigen presenting cell
IL-2 is secreted and binds to IL-2R on T cells –> receptor is activated
Division, differentiation, effector functions and memory

Lack of IL2 means lack of effector T cell therefore lack of cytotoxicity

29
Q

Malnutrition

A

Damages lymphoid tissue
- lymphoid atrophy

Affects thymus in children –> T cell abnormalities –> fewer T cells
Reduced SigA
Reduced complement
Reduced microbial killing

30
Q

Malnutrition

Zinc

Iron

Vitamin B6 and folate

A

Reduction in delayed type IV HS (cell mediated)
Low CD4 and CD8
Impaire Ab responses (low plasma cell numbers)

Iron dependent enzymes required for super oxide generation
Low iron causes ineffective microbial killing by phagocytes

Deficiency reduces cell mediated immunity

  • lymphocyte proliferation and Ab production
  • new immune cell production relies on sufficient Vit B6 and folate
31
Q

AIDS

A

Acquired immune deficiency syndrome

Due to HIV

32
Q

HIV infection of lymphocytes

A

Conformational change in structure allows virus to inject DNA into host cell
CD4 cells are required for this and macrophages as they have specific receptors for this purpose

33
Q

HIV

Asymp

CCR5

HTLV-1 PROTEIN

A

Needs to bind to CD4 and a chemokine receptor to gain entry into cells
- binds to CXCR4 and CCR5

Asymptomatic stage CCR5 is dominant and CXCR4 used as infection proceeds

Some have deletion of CCR5 - natural protection against HIV as virus cannot bind to its receptor
Deletion inhibits infection as receptor is non functional and rapidly degrades

Up-regulates CXCR4 and CCR5 –> accelerates disease

34
Q

Mechanism of HIV

Tx

Recurrent infections and more serious

A

Infects and kills CD4 cells

Anti HIV antibodies produced by proteins in HIV envelope change shape due to mutations –> ineffective

Symptoms can take 10 years

Monitor CD4 count by flow cytometry

Recurrent infections
Oral candidiasis
Varicella‐Zoster infection (Shingles)
Herpes Simplex Virus (oral & genital)
Cutaneous skin infections

Kaposi’s Sarcoma ‐ Tumour of endothelial cells – widespread in skin, mucous, visceral (gut & lungs) and lymph node disease occurs
Pneumonia ‐ Due to Pneumocystis jirovecii (formally P. carinii), Mycobacterium tuberculosis & fungal infections
Enteric bacteria – cause weight loss
Toxoplasmosis – protozoal infection – causes brain & neurological problems Cryptococcus neoformans – fungus that causes meningitis Cytomegalovirus – inflammation of brain & spinal cord

DEN303 - IHD (58 decks)

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