Immunodeficiency and infection

Question 1

What is immunodeficiency?

Answer 1

Immune system can’t protect host from pathogens

Question 2

Primary ID

Answer 2

Inherited/genetic or developmental defect in the immune system

Question 3

Severe combined immunodeficiency

Answer 3

Primary ID, genetic defect leads to lack of functional T and B cells in blood

Question 4

What are the four types of SCID

Answer 4

1) Mutation of cytokine or receptor affects T cell precursor signalling. IL-2 signals for IL-4,7,9,15,21
2) Defect in purine metabolism. When a cell lacks adenosine deaminase, it can’t convert adenosine/deoxyadenosine to inosine/deoxyinosine leaving toxic metabolites
3) Mutation in RAG1/2 or proteins involved in developing lymphocytes
4) Mutation of kinases disrupts pre-TCR or TCR signalling during T cell development

Question 5

What is DiGeorge syndrome?

Answer 5

Deletion of chromosome 22 causes thymus defect, reduced development of parathyroid and congenital heart abnormalities due to T-box transcription

Question 6

What is B cell immunodeficiency?

Answer 6

Decreased production of >1 AB isotope

Question 7

Symptoms of B cell immunodeficiency

Answer 7

Complete absence of mature B cells/plasma cells

Suffer from recurrent infection but display normal response against virus and fungi - T cell unaffected

Question 8

Bruton’s hypogammaglobulinaemia

Answer 8

X-linked
Low conc of IgG, no other ABs
No peripheral B cells 
Recurrent bacterial infections
Defect in Bruton's tyrosine kinase

Question 9

Leukocyte adhesion deficiency

Answer 9

Defect in the B chain common to LFA-1, MAX-1 and gp150/95
Leukocytes can’t adhere an don’t function correctly
Defect in T and B cell cooperation

Question 10

Chronic granulomatous disease

Answer 10

X-linked or autosomal recessive

Neutrophils don’t make superoxide (NADPH oxidase) so can engulf bacteria but not kill

Question 11

Complement deficiency

Answer 11

Failure to activate complement - increased susceptibility to bacteria

Question 12

Symptoms of primary ID

Answer 12

Recurrent infections
Trouble gaining weight
Comorbid conditions (delayed cord cutting)

Question 13

DDx PID

Answer 13

Acquired and non-immunological causes (CF)
Low IG due to loss of enteropathy, nephropathy or burns
HIV
Malnutrition (SID specific)

Question 14

SCID emergency treatment

Answer 14

Isolation 
No live vaccines
Ig therapy 
Enzyme replacement 
Haemopoetic stem cell transplantat

Question 15

Acquired ID

Answer 15

External agents - drugs, immunosuppressants, corticosteroids, malnutrition
HIV

Question 16

Sx acquired ID

Answer 16

Susceptible to common and opportunistic infections

Question 17

HIV

Answer 17

Retrovirus of lentivirus genus
Infects and kills CD4
Uses integrate to incorporate into genome
<200 CD4 = AIDS

Question 18

Diagnosis HIV

Answer 18

ELISA detects AB presence (gag p24)
PCR used in infants because of remnants from mum
Confirmed with western blot

Question 19

ABs and HIV

Answer 19

Occur 6-12 weeks after exposure

When they are detected, the person is seroconverted or seropositive

Question 20

AIDS diagnosis

Answer 20

HIV-1 in blood
<200 CD4
Impaired hypersensitivity
Opportunistic infections

Question 21

HIV/AIDs treatment

Answer 21

HAART combines drugs from different classes
Antibiotics
Immunisation