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Neural Biology 1 > immunodeficiency > Flashcards

immunodeficiency Flashcards

1
Q

what is immunodeficiency?

A
  • occurs when one or more two components of the immune system are defective
  • you can’t start acute inflammation
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2
Q

what are the two types of immunodeficiency?

A

. primary

. secondary

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3
Q

what is primary immunodeficiency?

A
  • caused by mutations in genes that produce proteins involved in immune response
  • caused by mutations affecting genes that control expression and activity of immune responses
  • often present from very young age
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4
Q

what is secondary immunodeficiency?

A
  • acquired
  • present at any age
    1. consequence of other diseases
    2. secondary to environmental factors (i.e. starvation/malnutrition)
    3. an adverse consequence of medical intervention
    e. g. steroids which induce immunodeficiency
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5
Q

how does immunodeficiency get diagnosed?

A

. patients with immune deficiency are usually detected clinically by a history of repeated infections with the same or similar pathogens this indicates immunodeficiency

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6
Q

what does the type of infection indicate?

A

. the type of infection indicates where the defect is in the immune system

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7
Q

what does it mean if you have repeated infection by pyogenic/pus forming bacteria?

A

. defect in antibody
. defect in complement system
. defect in phagocytic activity
e.g. macrophages aren’t working properly

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8
Q

what does it mean if you have a persistent fungal skin infection (cutaneous candidiasis ) or recurrent viral infection?

A

. defect in host defence mediated by T lymphocytes

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9
Q

what are the 5 ways of determining the competency of the immune system to diagnose the type of immunodeficiency?

A
  1. take a blood smear/sample to look for differences in white blood cell populations
  2. use fluorescent tags to target specific protein on the cell surface of each of white blood cells, this is called fluorescent activated cell sorting
  3. measurement of serum immunoglobulins (IgG)
  4. phagocytic competence leukocytes and monocytes
  5. complement activity is determined by testing the dilution of serum required for the lysis of 50% of antibody coated red blood cells
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10
Q

what is primary immunodeficiency caused by?

A

. caused by recessive genes which can be carried through generation

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11
Q

why is primary immunodeficiency more prevalent in males?

A

. recessive genes required two copies to be present to see a phenotype
. males who inherit a defective chromosome will manifest a disease
. females who have two X chromosomes will not show but are carriers
. rare occasions two defective genes inherited from heterozygous parent and show phenotype
. males have nothing in the y chromosome to counteract the mutation

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12
Q

why is primary immunodeficiency rare?

A

. because people who have display the phenotype will not live long to pass it on

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13
Q

what does primary immunodeficiency result in?

A

. low antibody levels
. defects in complement
. defect is phagocytic cells
. defects in T cells

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14
Q

what would happens as a result of low antibody level?

A
  1. low antibody levels will prevent opsonisation - innate immune systems isn’t particularly functional
  2. pyogenic bacteria - glycocalyx not recognised as foreign by receptors on macrophages and neutrophils to induce phagocytosis directly
    . this means that bacteria escape immediate elimination by innate immune response
    . eradicating bacteria requires antibody and complement opsonisation of the bacteria
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15
Q

what are the two ways that low antibody levels can happens?

A
  1. failure in antibody production from B-lymphocytes
    e. g. XLA
  2. failure in B cell receptor activation, so no switch between IgM production to IgG, IgE or IgA in B lymphocytes
    e. g. patients with hyper IgM syndrome
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16
Q

where is IgM found?

A

IgM is found on cell surface of naive B cells

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17
Q

what does defects in complement components do?

A

. defects in complement affect pathogen destruction and self regulation

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18
Q

what is function of complement?

A

. pathogen destruction

. self recognition

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19
Q

what happens if you have defects in complement components, esp. C3?

A

. results in many immunodeficiency diseases with similar phenotypes to those that inhibit antibody production/function
. limit ability for opsonisation
. defects in C3 or the cleavage of C3 to C3a and C3B inhibit opsonisation and subsequent phagocytosis

20
Q

what happens if you can’t produce one of the complement components C5-C9?

A

. this means that you can’t get MAC ( membrane attack complex forming)
. this means that you can’t have complement binding to the outside of bacteria and creating a pore through its cell membrane to induce lysis directly

21
Q

what does defect in MAC lead to?

A

. leads to susceptibility to neissera species of bacteria

. this is the main bacteria that caused meningitis and gonorrhea

22
Q

what happens due to defect in complement components ?

A
  • any protein can be made incorrectly and affect how the immune system is responding
  • can affect the recruitment of inflammatory cells, this is due to ineffective production of peptide mediators such cytokines
  • ineffective opsonisation of pathogens
  • ineffective MAC formation
23
Q

what happens if you have a defect in CD59 and DAF which is part of defects in complement self identity ?

A
  • these are exposed on your red blood cells

- you have misdirection of your complement system which will then target your red blood cells

24
Q

what happens if you have defects in C1-inhibitor?

A

. deficits lead to factor Xlla, kallikrein and C1r and C1s mis- regulation
. end result is an over expression of vasoactive mediators and subsequent oedema

. acute inflammation will not work properly

25
Q

what happens if you have defects in phagocytic cells?

A

you can get neutropenia

26
Q

what is neutropenia ?

A

. deficiencies in neutrophils
. two inherited types:

  1. severe congenital neutropenia- low neutrophil numbers-need for bone marrow transparent
  2. cyclic neutropenia - cycle between normal and low neutrophil numbers over a 21 day cycle
27
Q

what is the cause of a deficit in neutrophil migration?

A

. defects in E selectin, P selectin , ICM

28
Q

what happens when neutrophils loose the ability to phagocytose/kill intracellular pathogens?

A

. cannot endocytose

. cannot produce superoxide radicals
i.e chronic granulomatous disease

29
Q

what happens when you have defects in T cell function?

A

. T cell function lead to severe combined immunodeficiency

. T cells essential in a adaptive immunity
- defects lead to no T cell dependant antibody response nor T-cell mediated immune responses

. cannot develop immunological memory
. severe combined immunodeficiency (SCID)

30
Q

what are the types of severe combined immunodeficiency (SCID)?

A

. X linked SCID

  1. T cells fail to develop due to mutations in gamma chain of cytokines receptors
    . cannot respond to inflammatory mediators

2.. autosomally inherited SCID

. accumulation of toxic nucleotide metabolites occur with defects in purine degradation
. theres are two types
1. adenosine deaminase deficiency (ADA)
2. purine nucleotide phosphorylase deficiency (PNP)

. nucleotide metabolite accumulation is toxic to developing T cells and kills them off

  1. MHC class II deficiency - lack of MHC class 11 protein at cell surface
    . your antigen presenting cells cannot present what’s going on in the environment to the T cells
    . T cells cannot be activated
    . leads to susceptibility to severe infections and frequently , death in early childhood
4.MHC class I deficiency 
. cytotoxic T cell cannot identify wether that cell has got a viral infection or has got a fungal infection 
. signs: recurrent bacterial infections confined to the respiratory tract evolving into chronic inflammatory lung disease and bronchiectasis
31
Q

how can you correct gene defects?

A

. bone marrow transplantation or gene therapy can be tools to correct genetic defects resulting in immunodeficiency’s
. you take healthy stem cells from somebody else and you put them back
. healthy stem cell will be able to populate the immune system
. B and T cells are produced by new bone marrow
. HLA must be similar of makeup, so that B and T cells being produced can interact with the HLA on the other cells of your body

32
Q

what is the issue with bone marrow transplants?

A
  • risk of host versus graft disease
  • if mature T cells from host recognise graft as foreign if not enough MHC cross over
  • often avoided by irradiating host bone marrow prior to transplant
  • SCID are immunodeficient anyway so no need to irradiate
33
Q

what is gene therapy?

A
  • way of taking out cells with defective gene and then you can use a virus into your genetic material to introduce a normal coding region of DNA, put cells back into the body to undergo transcription and translation and then you can actually produce proteins which are normal
    1. extract immunodeficient bone marrow cells
    2. insert a normal copy of the gene
    3. reinfuse bone marrow
34
Q

what is acquired immunodeficiecny?

A

. common disease
. some pathogens suppress the immune responses
- staphylococci produce toxins that act as super antigens - bind to a lot of T cells and overstimulate and proliferate-enter apoptosis early. results fewer functioning T cells
- commonly associated with viruses
. measles - viral infection causes T and B cell function to decrease for several months
. allows subsequent bacterial infections to run wild
TB

35
Q

what is opportunistic pathogen?

A
  • immunosuppression caused by viruses often leads to an infection by an opportunistic pathogen
  • pathogen that we are exposed to constantly
  • this is the thing that causes most illness and possible death
36
Q

what can lead to secondary acquired immune deficiency ?

A 
. cancer (i.e. leukaemia)
. diabetes and other metabolic diseases - neutrophil dysfunction
. malnutrition
. chronic infection
. adverse complication of medical intervention 
such as 
chemotherapy
radiation therapy
immunosuppressive drugs
37
Q

what is the case study for acquired immune deficiency ?

A
  • AIDS ( acquired immune deficiency syndrome )
  • previously healthy, presenting with opportunistic pathogen infections such as pneumocystis carinii pneumonia and toxoplasmosis
  • caused by HIV-1, HIV-2
  • HIV is transmissible through seminal fluid, vaginal fluid, breast milk and blood
  • HIV is a retrovirus which infects T-helper (CD4+) lymphocytes which causes a profound immunodeficiency
  • also infects dendritic and macrophages
38
Q

what does HIV cause?

A

. HIV can cause an acute inflammatory response that is resolved and as a consequence induced lasting immunity
. when you first get infected with HIV , it suppresses your immune system so you end up with flu like symptoms , most T-cell will die
. virus doesn’t kill all T-cells, it lies dormant in some of those T-cells
- after a while immune system can come back to normal
. then you enter clinical latency period where everything is running smooth because the virus is slowly replicating
. when exposed to opportunistic pathogen then you can die
- HIV px can also die from cancer

39
Q

what is the effect of the genetic variation in HLA type?

A
  • genetic variation in HLA type of the host modifies disease outcome
  • HLA-B57
    and HLA-B27 - better prognosis - slower progression
  • HLA-B35- worse prognosis - faster progression
40
Q

what are the three mechanisms for loss of T helper cells in HIV?

A
  1. direct viral killing of infected cells - necrosis
  2. increased susceptibility to induction of apoptosis in infected cells
  3. killing of infected T helper cells (CD4+) by cytotoxic T cells (CD8+) that recognise displayed viral particles through MHC 1
41
Q

what are types of diseases caused by opportunistic pathogens?

A

. oral candidiasis ( oral thrush )
. shignles
. TB ( bacterial -lungs)
. cotton wool spots in the retina

42
Q

what are examples of ocular opportunistic infections?

A
  1. cytomegalovirus retinitis
  2. candida endophthalmitis
  3. toxoplasma retinochoroiditis
43
Q

what is cytomegalovirus retinitis?

A

.15-40% HIV patients
. virus infects retinal cells leading to necrosis
. gets to retinal cells because its blood born
. infects vascular endothelium which spreads to the retinal cells
. you have impaired CD4+ cells, this permits the uncontrolled cytomegalovirus replication
. as virus replicates leads to necrosis of retinal cells
. weakens the blood-brain barrier - end up with blood haemorrhages
. loss of central vision because those retinal cells in the macular are dying off

44
Q

what is toxoplasma retinochoroiditis ?

A

. caused by an intercellular pathogen called toxoplasma gondii which is a protozoan parasite
. can caused by ingestion of the oocytes ( eggs of these parasites ) which are shed in faeces of a cat
. can also be caused by the consumption of tissues which cause tissue cysts from meat products
. gets to the eye because its blood born
. can spread to vitreous and cause vitritis

45
Q

what is candida endophthalmitis?

A

. caused by fungus candida albicans
. blood born infection
. infection comes through the retina
. van spread to the vitreous- causes floaters in vitreous
. whitish “puff-balls” and vitreal strands

46
Q

how is immunodeficiency linked to cancer?

A
  • immunodeficiency increases risk of cancer development
  • cancer cells can be recognised by immune system and killed
  • if the immune system is compromised, more cancer cells will get through bodies control system

Neural Biology 1 (58 decks)

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