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Y3 immunology and haematology > 1y immunodeficiency > Flashcards

1y immunodeficiency Flashcards

1
Q

immune cell development

A

pluripotent stem cells differentiate into different types of immune cells (thymus/bone marrow) –> pre myeloid, lymphocyte committed stem cells, pre monocyte cells

pre myeloid - precursor for neutrophils

lymphocyte committed stem cells - precursors for T and B cells

pre monocyte cells - develop into monocytes and macrophages

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2
Q

what are the different types of T cells

A

effector and suppressor T cells

CD4 - Th1, Th2, Th17, regulatory T cells

regulatory CD8 cells

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3
Q

what are B cells responsible for

A

producing antibodies

once they start secreting antibodies they become plasma cells

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4
Q

what are the 2 types of immune responses

A

specific vs non specific

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5
Q

what defence is involved in specific immunity

A

antibody - plasma cells

cellular immunity - T cells and APCs

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6
Q

what defence is involved in non-specific immunity

A

complement

phagocytes

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7
Q

what usual organisms are isolated in antibody defence

A

pyogenic bacteria - staphylococci, streptococcus pnuemoniae, haemophilus influenzae

some viruses: enteroviruses - polio, ECHO

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8
Q

what usual organisms are isolated in cellular immunity defences

A

viruses - cytomegalovirus, herpes zoster, measles, papilloma

fungi - candida, aspergillus, pneumocystis

bacteria - myobacteria, listeria

protozoa - cryptosporidium

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9
Q

what usual organisms are isolated in complement defence

A

pyogenic bacteria

neisseria

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10
Q

what usual organisms are isolated in phagocyte defence

A

bacteria - staphylococci, gram -ve

fungi - aspergillus, candida

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11
Q

which is more specific: innate or adaptive immunity

A

adaptive

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12
Q

serum immunoglobulin levels through life (pre-natal to 10yrs)

A

for the 1st 6mths of life the main source of antibodies are the maternal antibodies that pass through the placenta

babies gradually start building their own antibodies with age

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13
Q

what does immunodeficiency mean

A

defects in any one or more components of the immune system

can lead to serious and often fatal disorders

collectively known as immunodeficiency diseases

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14
Q

why is the immune system important

A

integrity of the immune system is essential for defence against infectious organisms and their toxic products

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15
Q

classes of immunodeficiency diseases

A

1y or congenital

2y or acquired

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16
Q

what is the major consequence of immunodeficiency

other consequences

A

increased susceptibility to infection

also susceptible to certain types of cancer

certain immunodeficiencies are associated w/ an increased incidence of autoimmunity

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17
Q

what causes 1y immunodeficiency

A

genetic, congenital disorders - mainly caused by genetic aberrations

small number caused by autoimmunity

part of the immune system is missing/functioning abnormally

not 2y to other disease processes, toxins or drugs

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18
Q

what does 1y immunodeficiency predispose to

A

infections

tumours

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19
Q

where can the abnormality be in 1y immunodeficiency

A

components of the innate immune system

stages of lymphocyte development

responses of mature lymphocytes to antigenic stimulation

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20
Q

when to suspect immune deficiency

A

children - more than 3-4 infections each year or unusual infections or difficult to treat infections

adults - more frequent infections, more severe infection

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21
Q

defects in lymphocytes in 1y immunodeficiency

A

can happen at any level

the earlier the defect is in the process of development, the more severe the disease

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22
Q

what happens if there is a defect in TCR signalling

A

T cell receptor signalling

defect in antigen presentation, processing and recognitiion

defect in immune response

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23
Q

what does the increased susceptibility to infection in immunodeficiency depend on

A

the component of the immune system that is defective

indicates which infection the patient will be more susceptible to

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24
Q

what does the type of opportunistic infection present give us a clue to

A

degree and cause of immunodeficiency

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25
what would repeated infection w/ encapsulated bacteria indicate
defective antibody production mild immunodeficiency
26
what can antibody deficiency result in
IgG and IgA deficiency can lead to recurrent resp infection pneumococcus/haemophilus spp
27
what are infections w/ staphylococci/gram -ve bacteria/fungi associated w/
reduced number/function of phagocytes
28
what can complement defects predispose to
neisseria infection and encapsulated bacteria
29
what can defects in T cells or macrophages predispose to
infection w/ intracellular organisms - protozoa, viruses and intracellular bacteria incl mycobacteria
30
T cell immunodeficiency and mycobacterial infection - severity of immunodeficiency - infection
severity of T cell immunodeficiency is reflected in patterns of mycobacterial infection in mild T cell immunodeficiency it is able to invade the body outside the lungs more severe immunodeficiency predisposes to widespread infection w/ mycobacteria of low virulence normally found in the environment
31
what is mycobacterium tuberculosis
virulent organism causes lung infection in immunocompetent people
32
what is reactivation of latent herpes infection linked to
T cell immunodeficiency recurrent attacks of coldsores (HSV) or shingles (HZV) may suggest mild immunodeficiency
33
what is recurrent candida infection suggestive of
defects in the Th17 pathway
34
examples of viral induced tumours | what are they characteristic of
herpes virus induced tumours - Kaposi sarcome (HHV8) non-Hodgkin lymphoma - EBV T cell dysfunction
35
3 causes of 1y immunodeficiency
mutations polymorphisms polygenic disorders
36
what is a mutation
permanent alteration in the DNA sequence that makes up a gene - the sequence differs from what is found in most people mutations affecting the immune system are rare, can affect any part of the immune system and cause severe disease
37
what are polymorphisms
involves one of two or more variants of a particular DNA sequence - aka alleles of the same gene occurring at a single locus in at least 1% of the pop most common polymorphism involves variation at a single base pair can also be much larger in size and involve long stretches of DNA
38
polymorphisms in the immune system
common traits that affect any part of the immune system and cause a moderate increased risk for infection not usually as severe as diseases associated w/ mutations
39
what are polygenic disorders
disorders caused by the combined action of more than one gene
40
polygenic disorders of the immune system
relatively common disorders of the immune system and affect mainly antibodies some of these polygenic conditions may be caused by autoimmunity
41
what condition do many mutations result in
severe combined immunodeficiency (SCID)
42
what is SCID
group of disorders that affect both T and B cells
43
prognosis of SCID
infants die within the first few mths of life unless treatment is given
44
genetics of SCID
some are autosomally inherited and there may be a hx of consanguinity other types are X linked and there may be a hx of early deaths in maternal uncles
45
treatment for SCID
stem cell transplant can be a cure - has to be done quickly if performed very soon after birth 90% survive if delayed for a few mths - 50% survive many countries screen for SCID in newborns
46
what can polymorphisms result in
human leukocyte antigen (HLA) alleles are polymorphic and affect the outcome of infections polymorphisms in mannan-binding lectin (MBL) and complement affect the risk for infections
47
impact of non-functioning HLA alleles
individuals w/ HLA alleles that are unable to bind viral peptides have a worse outcome
48
what is MBL
collagen-like protein that binds sugars in bacterial cell walls and activates the classic complement pathway
49
examples of polygenic disorders
common variable immunodeficiency (CVID) IgA deficiency specific antibody deficiency - relatively common polygenic disorders that affect antibody production
50
how common is CVID
most common 1y immunodeficiency requiring treatment occurs in ~1/20 000 young people M+F
51
immune features of CVID
low levels of total IgG | IgA, IgM levels and B/T cell numbers are variable
52
clinical features of CVID
recurrent resp tract infections gut, skin and nervous system infections autoimmunity is common many pts have hx of other affected family members or of consanguinity - autosomal recessive inheritance
53
what happens to pts w/ specific antibody deficiency
recurrent infections w/ pneumococcus/haemophilus spp despite normal total IgG don't respond to polysaccharide agents and have poor titres of antibodies to pneumococcal antigens even after vaccination
54
example of 1y immunodeficiency caused by autoimmunity - polygenic
pts w/ autoimmune polyendocrinopathy candidiasis ectodermal dysplasia (APECED) frequently experience severe recurrent candida infection - defect in central tolerance and experience many types of autoimmunity
55
what differences in immune system do pts w/ APECED have
some pts w/ APECED produce antibodies against IL-17 --> impaired responses to candidiasis other individuals who have no genetic defects produce antibodies against IFN-gamma - recurrent problems w/ mycobacterial infection
56
autosomal recessive SCID - genetics - cell/pathway - defect - main type of infection
monogenic T and B cells recombinase (RAG) mutations all pathogens
57
Wiskott-Aldrich syndrome - genetics - cell/pathway - defect - main type of infection
monogenic T and B cells actin cytoskeleton all pathogens
58
X-linked SCID - genetics - cell/pathway - defect - main type of infection
monogenic T and NK cells reduced, B cells not functional cytokine receptor common gamma chain all pathogens
59
DiGeorge syndrome - genetics - cell/pathway - defect - main type of infection
monogenic T cells absent thymus intracellular pathogens
60
anti-IL-17 - genetics - cell/pathway - defect - main type of infection
autoantibodies T cells TH17 responses candida
61
anti -IFN gamma - genetics - cell/pathway - defect - main type of infection
autoantibodies T cells Th1 responses mycobacteria
62
hyper IgM syndrome - genetics - cell/pathway - defect - main type of infection
monogenic B cells mutations in CD154 pneumococcus and haemophilus
63
X-linked antibody deficiency - genetics - cell/pathway - defect - main type of infection
monogenic B cells mutations in BTK pneumococcus and haemophilus
64
CVID - genetics - cell/pathway - defect - main type of infection
polygenic B cells unknown defect pneumococcus and haemophilus
65
IgA deficiency - genetics - cell/pathway - defect - main type of infection
polygenic B cells unknown defect pneumococcus and haemophilus
66
specific antibody deficiency - genetics - cell/pathway - defect - main type of infection
polygenic B cells unknown defect pneumococcus and haemophilus
67
TAP defects - genetics - cell/pathway - defect - main type of infection
monogenic antigen presentation impaired antigen processing all pathogens
68
HLA - genetics - cell/pathway - defect - main type of infection
polymorphisms antigen presentation viruses
69
complement deficiency - genetics - cell/pathway - defect - main type of infection
monogenic complement membrane attack complex bacteria - esp Neisseria
70
MBL - genetics - cell/pathway - defect - main type of infection
polymorphisms complement cascade many pathogens
71
chronic granulomatous disease - genetics - cell/pathway - defect - main type of infection
monogenic phagocytes oxidative burst staphylococci and invasive fungi
72
diagnosis - clinical presentation of SCID
children - defective T cells and B cells, develop infections in the first few wks of life unusual/recurrent infection diarrhoea unusual rashes
73
diagnosis - SCID hx
FHx neonatal death | FHx consanguinity
74
diagnosis - SCID lymphocyte count
very low total lymphocyte count - <1x10^9/L lymphocyte numbers should be measured by flow cytometry
75
diagnosis - clinical presentation of antibody deficiency
presents later in life some forms e.g. CVID don't present until adulthood chronic/recurrent bacterial resp infection
76
diagnosis - antibody levels in antibody deficiency
measure IgG, IgA, IgM w/ low levels of immunoglobulins, causes of 2y immunodeficiency should be excluded if total Igs are normal, measure specific antibodies against haemophilus and pneumococcus if these tests are all normal, it is important to check no problems are apparent w/ complement/neutrophil function
77
aim of treatment of 1y immunodeficiency
prevent infection
78
treatment of 1y immunodeficiency
mild immunodeficiency - prophylactic abx may be adequate more severe antibody deficiency - immunoglobulin replacement therapy
79
what is immunoglobulin therapy
antibodies against a wide range of pathogens Ig pooled from thousands of normal donors Ig replacement can be given IV or SC plasma screened for HIV, hep B and C antibodies
80
treatment of SCID
if confirmed - definitive treatment until definitive treatment, avoid serious infection stem cell transplant for SCID and most T cell deficencies
81
steps to avoid serious infection in SCID
avoid live vaccines - MMR, polio prophylaxis against opportunist infections e.g. pneumocystis jiroveci
82
stem cell transplants
most successful if done within wks of birth before the infant has developed any infection - if this is possible, 90% success rate and curative when SCT isn't an option - attempt gene therapy
83
gene therapy for 1y immunodeficiency
uses recombinant technology to correct the genetic defect in the pts own stem cells which can then reconstitute the immune system used in pts w/ SCID for whom no suitable stem cell donor was available
84
what criteria must be met for gene therapy to be successful
1. genetic mutation for each pt must be identified and there must be evidence that correcting the mutation will improve the condition 2. transfected gene must confer a proliferation/survival advantage 3. gene therapy mustn't cause malignancy
85
gene therapy in X linked SCID

Y3 immunology and haematology (20 decks)

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