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IMMUNOLOGY PART 1 DEN303 > Immunodeficiency > Flashcards

Immunodeficiency Flashcards

1
Q

Define primary immunodeficiency

A

Intrinsic genetic defects in the immune system

Affects T and B cells, complement and phagocytosis

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2
Q

Define 2ndry immunodeficiency

A

External factors affecting the immune system

Drugs, malnutrition, viral infec

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3
Q

What is primary immunodeficiency?

A

Absence/failure of normal function in one or more elements of the immune system = increased susceptibility to infec

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4
Q

What is specific immunodeficiency?

A

Abnormalities of T or B cells - adaptive immune system

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5
Q

What is non-specific immunodeficiency?

A

Abnormalities of phagocytes or complement - innate immune system

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6
Q

What are the categories of immunodeficiencies? - Primary immunodeficiency

A
  1. Defects in Ig, C’, phagocytes = susceptible to bac infecs (H.influenzae)
    = Pyogenic infecs - pus formation
  2. Defect in cell mediated immunity (T cells) = susceptible to commensal organisms (candida, viruses)
    = Opportunistic infecs
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7
Q

Examples of B cell deficiencies?

A

IgA deficiency, common variable immunodeficiency

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8
Q

What was the 1st immunodeficiency disease discovered?

Features of this?

A

X-linked Agammaglobulinemia (X-LA)
Genes on X chromosomes = affects male
Tend to have no B cells, tonsils, little IgG in serum

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9
Q

X-linked recessive inheritance?

A

More frequent in males as they only have 1 X chromosome
Females need a copy of defective gene from both parents to have a recessive disease
Females = 1 copy = carrier
X-linked recessive genes passed from female carriers to their ill sons and carrier daughters
Ill males = pass gene to daughter

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10
Q

X-linked dominant inheritance?

A

Less common
Dominant gene on X-chromosome
1 gene causes disorder
Mother passes mutated gene to offspring

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11
Q

X-linked dominant inheritance - what percentage of children will have the disease and not have it?

A

50% of children (25% male, 25% female) will have the disease

50% unaffected

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12
Q

What occurs if a man with an X-linked dominant disorder has children?

A

Son not affected

Daughters will inherit condition

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13
Q

How is X-linked Agammaglobulinemia (X-LA) caused?

A

Defective btk gene that encodes a B cell tyrosine kinase
btk important in maturation of B cells
No B cell maturation = no IgG = poor Ab response

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14
Q

How to treat X-linked Agammaglobulinemia (X-LA)?

A

First 6-12 months of life have protected maternal IgG
Get recurrent pyogenic infecs
Therapy - repeated injections of gamma-globulin throughout life

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15
Q

Hyper‐IgM Immunodeficiency?

A 
Deficient in IgG and IgA but hyper IgM
X linked recessive condition with mutations in CD40 = important for class switching = IgM turns to IgG so can not switch 
Susceptible to pyogenic infecs and autoimmune disease
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16
Q

IgA deficiency?

A

Most common (1 in 700 caucasians)
Failure in terminal diff of B cells to plasma cells
Individs develop type III hypersensitivity
Susceptible to pyogenic infecs

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17
Q

Examples of T cell deficiencies?

A 
Severe combined immunodeficiency
MHC class II def
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18
Q

Severe combined immunodeficiency (SCID)?

A

Individs with no/poor T cell func
BUT B cell func depends on T cel func = T cell deficient individuals have poor T cell and humoral functions
= Commensal organism infec - Oral candidiasis due to candida albicans infec

Few lymphocytes
More common in males
Infants die within first 2yrs of life without bone marrow transplant - usually sibling/parent to avoid graft rejection

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19
Q

DiGeorge syndrome?

A

T cell deficiency due to affected thymus in foetal dev

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

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20
Q

MCH II deficiency?

A

= failure to expess MHC II antigens on APC
As CD4+ cells required MCHII for positive selection of thymus = infants deficient in MHC II have no CD4+ cells
= deficiency in Ab

21
Q

Complement deficiencies?

A

Deficient in C3, factor H and I = increase pyogenic infecs
Deficient in MAC = increase Neisseria infects
Most common is hereditary angioneurotic edema (HAE)

22
Q

Hereditary angioneurotic edema?

A

Most important C’ deficiency
C1 inhibitor - inhibits activation of C1
Inhibits C’ and elements of kinin/clotting system
= severe oedema due to plasma leakage and recurrent swelling
Intestine - abdominal pains and vomiting
Upper airways - choke and death

23
Q

Defects in phagocytes can affect..?

A

Neutrophils and macrophages

= Neutropenia = severe pyogenic infecs

24
Q

Name 2 genetic defects that are often fatal?

A

Chronic granulomatous disease

Leukocyte adhesion deficiency

25
Q

How to diagnose chronic granulomatous disease?

A

Inability of phagocytes to reduce NBT dye
Healthy phagocytes = ROS reduces it to a purple colour
Pt with CGD = dye stays yellow

26
Q

Leukocyte Adhesion Deficiency (LAD) type 1?

A

Deficient for CD18
Defective C’ receptor 3 = binds to bac opsonised with C3bi - increase phagocytosis
Cannot phagocytose opsonised bac = recurrent infecs

27
Q

Leukocyte Adhesion Deficiency (LAD) type 2?

A 
Defective receptors (CD15) that bind selections
Phagocytes cannot roll on the ednothelium
28
Q

What causes 2ndry immunodeficiency?

A

External affects on immune system - drugs, nutrition, viruses, burns

29
Q

What can corticosteroids - glucocoticoids cause?

A

Changes in leukocytes in circulation after treatment
Lympocytopenia - T cells affected more
Monocytopenia - quick but back to normal by 24hrs
Neutrophilia - due to release of mature neutrophils from bone marrow

30
Q

What occurs with a repeated dose of corticosteroids - glucocoticoids?

A

Low lymphocytes, lack of Ab and defective cytokine synthesis

31
Q

What can anti-cancer therapy - radiotherapy cause?

A

DNA strands break
Increase apoptosis and stops proliferation
Targets cancer cells but also affects bone marrow and lymphoid tissue
Stops immune cell production, prolif and diff
Susceptible to organisms normally not pathogenic

32
Q

What can anti-cancer therapy - chemotherapy cause? Drugs used to do this?

A

Cyclophosphamide
- Activated inside body = crosslinks DNA to stop cell prolif and increase apoptosis
Mainly affects lymphocytes (B calls mostly)
Loss of cell mediated and Ab production

Azathioprine
= converted to 6-mercaptopurine in body then metabolised to thioinosinic acid
= gets incorporated into DNA and stops DNA replication and proliferation

33
Q

How does 5-Fluorouracil work?

A

5FU blocks thymidine synthesis which is a nucleotide required for DNA replication
5FU gets incorporated into DNA and RNA = induces cell cycle arrest and apoptosis
Affects T and B cells and NK cell numbers

34
Q

Why is cyclosporin used in organ transplantation?

A

Immunosuppressant to reduce activity of immune system and prevent organ rejection
Particularly affects T cells by affecting IL-2 production

35
Q

What produces cyclosporin?

A

Produced by fungus beauveria nivea

36
Q

How does T cell Ag recognition occur and how is it activated? Once activated, what occurs?

A

Involves CD28 on T cell binding to CD80 on APC
IL-2 secreted and bind to IL-2R on T cells
= division, diff, effector funcs and memory

37
Q

What is Rapamycin (Sirolimus)? It’s uses?

A

Immunosuppressant drug used to prevent rejection in organ transplantation - especially kidney transplants as low toxicity

38
Q

What is the most common cause of immunodeficiency? What does it cause?

A 
Malnutrition= damages lymphoid tissue
Lymphoid atrophy
Thymus affected in children - T cell abnormalities
Reduced number of CD4+ cells 
Reduced sigA
Reduced C' levels
Reduced microbial killing by phagosomes
39
Q

What does zinc malnutrition cause?

A

Decrease in type 4 hypersensitivity
Low CD4 and CD8 numbers
Impaired Ab responses

40
Q

What does iron malnutrition occur?

A

Iron‐dependent enzymes required for superoxide generation

Ineffective microbial killing by phagocytes

41
Q

What does vitamin B6 and folate deficiency cause?

A

Reduce cell mediated immunity, especially lymphocyte proliferation and Ab production

42
Q

What causes AIDS?

A

Human immunodeficiency virus (HIV)

43
Q

How does HIV infect cells?

A

HIV binds to CD4 and a chemokine receptor = gains entry into permissive cells
X4 (T-cell tropic) - CXCR4
R5 (M-cell tropic) - CCR5
In asymptomatic stage CCR5 predominates - as infection proceeds HIV uses CXCR4
CCR5 Δ32 deletion inhibits infection bcos the receptor is non-functional and rapidly degraded
HTLV-1 Tax protein up regulates CXCR4 and CCR5, may accelerate HIV disease

44
Q

How does HIV infect lymphocytes?

A

CD4 binding
CXCR4 binding
Fusion of peptide exposure

45
Q

What does HIV do?

A

Infects and kills Th (CD4) cells

Anti-HIV antibodies produced by proteins in HIV envelope change shape due to mutations = Ab not effective

46
Q

How long can HIV take to show symptoms?

A

10 yrs

47
Q

How to monitor CD4 count?

A

Flow cytometry

48
Q

Name some recurrent infections

A

Oral candidiasis
Shingles
Herpes simplex virus
Cutaneousa skin infecs

IMMUNOLOGY PART 1 DEN303 (5 decks)

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