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0V015 Biology & Pathology > Immunodeficiency L12 > Flashcards

Immunodeficiency L12 Flashcards

1
Q

When does immunodeficiency occur?

A

When one or more components of the immune system are compromised

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2
Q

What are the 2 groups of immunodeficiency?

A

Primary and secondary

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3
Q

What is the key difference between primary and secondary immunity?

A

Primary is genetic (caused by mutations) whereas secondary is acquired

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4
Q

Ho can secondary immunodeficiency be acquired?

A 
A consequence of other diseases 
Environmental factors (starvation/malnutrition)
An adverse consequence of medical intervention
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5
Q

How can immunodeficiency be detected?

A

Via assessing whether there is a repeated history of infections with the same or similar pathogens.

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6
Q

How can we identify where the defect in the immune system lies in someone who has immunodeficiency?

A

The type of infection indicates where the defect lies

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7
Q

A repeated infection by pyogenic/pus-forming bacteria suggests a defect in…

A

One or a combination of the following:

Antibodies
Complement system
Phagocytic activity

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8
Q

Persistent fungal skin infections or recurrent viral infections suggest a defect in…

A

T Lymphocytes

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9
Q

How can we diagnose the type of immunodeficiency?

A
  1. Taking a blood smear and counting the population of each blood cell type
  2. FACS ( fluorescent activated cell sorting) - different cells have different receptors and proteins on their surface which the fluorescent tags attach themselves to allowing us to identify the cell type.
  3. Measurement of serum immunoglobulins (IgG)
  4. Phagocytic competency of leukocytes and monocytes- expose to conditions in which they need to phagocytose material and asses how well they do that per a certain amount of time and compare to ‘healthy’ leukocytes
  5. Complement activity is determined by testing the dilution of serum required for the lysis of antibody coated RBCs
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10
Q

What are most inherited immunodeficiency diseases caused by?

A

recessive genes - carried on X chromosome and so more likely to show in males (sex-linked)

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11
Q

What is an issue with using a blood smear to identify type of immunodeficiency?

A

It can be hard to identify the different cell types especially between B and T lymphocytes.

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12
Q

What can primary immunodeficiency result in?

A

Low antibody levels
Defects in complement system
Defects in phagocytic cells (migration or phagocytosis)
Defects in T cells

( essentially any part of the immune system as all it takes is for a protein to be coded wrong)

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13
Q

Low antibody levels mean one is prone to what pathogen and why?

A

Pyogenic bacteria - glycocalyx (glycoprotein covering membrane of the bacteria) is not recognised as foreign by receptors on macrophages and neutrophils thus phagocytosis is not induced and so it escapes immediate elimination by innate immune system.

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14
Q

Why do low antibody levels result in persistent baterial infections?

A

Eradicating bacteria requires antibody and complement opsonisation of the bacteria.

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15
Q

How may low antibody levels arise?

A

Faliure in development or activation of B lymphocytes (that are stimulated to produce antibodies)

Failiure in antibody production ( B lymphocyte may be activated successfully but cant produce antibodies)

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16
Q

What is an example of a disease relating to antibody production faliure?

A

X-linked agammaglobulinemia (XLA - is acceptible as an acronymm)

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17
Q

How may failure to activate B lymphocytes occur and what does this cause?

A

B cell receptor fails to become activated and so there is no switch between IgM production to IgG, IgE or IgA which normally happens upon exposure to a pathogen.

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18
Q

Where is IgM found?

A

On cell surface of naive B cells

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19
Q

What do defects in the complement system affect?

A

pathogen destruction and ‘self’ regulation

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20
Q

How can defects in complement system affect pathogen destruction?

A

Defects in complement system C3 result in an inability for opsonisation.

Defects in complement components involved in MAC formation prevent MAC cell destruction thus can’t induce lysis and kill pathogen.

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21
Q

How can defects in complement system affect self identification?

A

Complement ‘control proteins regulate complement from binding to self cells i.e. stopping the accidental destruction of self cells however defects in this can result in self blood cells being targetted by complement as RBCs are always exposed to complement in blood!

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22
Q

What is Neutropenia

A

Deficiencies in Neutrophils

23
Q

What are the two types of neutropenia?

A

Severe congenital neutropenia

cyclic neutropenia

24
Q

What occurs in severe congenital neutropenia?

A

Extremely low neutrophil numbers

25
Q

What occurs in cyclic neutropenia?

A

Cycle between normal and low neutrophil numbers over a 21 day cycle - periodicity of being succeptible to pathogens.

26
Q

What treatment may be used for severe congenital neutropenia?

A

Bone marrow transport

27
Q

What can cause defects in phagocytic cells?

A

Neutropenia
Defects in neutrophil migration - mutations in any proteins involved in neutrophil extravasation
Inability to phagocytose/Kill intracellular pathogens

28
Q

How can an inability to phagocytose occur?

A

The phagocytes can’t engulf ( cannot endocytose)

Can’t produce superoxide radicals i.e. cell can engulf but can;t produce lysosomes to digest pathogen thats currently engulfed.

29
Q

What disease is an example of phagocytic cells being unable to produce lysosomes?

A

Chronic granulomatous disease

30
Q

What do defects in T cell function lead to?

A

Severe combined immunodeficiency (SCID)

Defects lead to no T cell dependent antibody response nor a T cell mediated response.

Thus patient cannot develop immunological memory ( no proper T memeory cells )

31
Q

What is X-linked SCID?

A

This is where T cells fail to develope due to mutation in common gamma chain of cytokine receptor thus cannot respond to inflammatory mediators to induce them to become actiavted T cells

32
Q

What is autosomally inherited SCID?

A 
A build up of toxic purine metabolites occur which kills T cells as a result of purines not being broken down properly.
This is caused by ADA ( adenosine deaminase deficiency) 
and PNP (purine nucleotide phosphorylase deficiency (PNP)
33
Q

SCID can be caused by deficiencies in what classes of MHC?

A 
MHC class 1 
MHC class 2
34
Q

What happens in MHC class I deficiency?

A

The MHC class protein is present at normal levels however there is a defect in presentation to the cell surface so T cells cannot be activated to destroy cells that has been infected by pathogen.

35
Q

What happens in MHC class II deficiency ?

A

There is a lack of MHC class II protein at cell surfaces so APC can’t present thus T cells can’t be activated.

36
Q

How can gene defects be corrected to ‘fix’ immunodeficiency?

A

Bone marrow transplant or gene therapy

37
Q

What is needed in order for successful bone marrow transplant?

A

Matching MHC

38
Q

What are B and T cells produced from the bone marrow of the donor referred to as?

A

Graft

39
Q

How can host versus graft cell occur?

A

Mature T cells from host recognise graft as foreign if not enough MHC crossed over.

40
Q

How may Host versus graft disease be avoided?

A

Iradiating host bone marrow

41
Q

How does somatic gene therapy work?

A

Extract immunodeficient bone marrow cells
insert a normal copy of the gene
reinfuse bone marrow

42
Q

How can immunodeficiency be acquired?

A

some pathogens supress immune responses

43
Q

Give an example of a pathogen that supresses immune responses

A

Staphlococci produce toxins that act as superantigens -bind to a lot of T cells and overstimulate T cells causing them to proliferate. ( If they proliferate too fast apoptosis is induced). Resulting in fewer T cells.

44
Q

Immunosuppression leads to infection by an…

A

opportunistic pathogen

45
Q

What is an oportunistic pathogen?

A

A pathogen that would normally be killed off easily by the immune system.

46
Q

Secondary immune deficiencies may be encountered in individuals with…

A 
Cancer i.e. leukaemia 
Diabetes and other metabolic diseases e.g. neutrophil dysfunction 
Malnutrition 
Chronic Infection 
Adverse complication of medical intervention :
-chemotherapy 
-radiotherapy 
-immunosuppressive drugs
47
Q

What does AIDS stand for?

A

Acquired Immuno deficiency syndrome

48
Q

What is aids caused by?

A

HIV ( Human immunodeficiency virus)

49
Q

What type of virus is HIV ?

A

A retrovirus which affects T helper cells , macrophages and dendritic cells

50
Q

How is HIV not ‘wiped’ out by the immune system?

A

It lays dormant in cells

51
Q

What are some examples of opportunistic pathogens?

A

Oral candidiasis (oral thrush ) - a fungal infection
Shingles ( VZV) - virus
TB- bacterial

52
Q

What are some examples of ocular opportunistic infections?

A

Cytomegalovirus - virus infects retinal cells leading to necrosis
Toxoplasma Retinochoroiditis - protozoan parasite
Candita Endopthalmitis

53
Q

Why does immunodeficiency increase the risk of cancer?

A

Normally cancer cells can be identified by immune system and killed however if immune system is compromised this will fail to happen and so more cancer cells will get through the bodies control system.

0V015 Biology & Pathology (57 decks)

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