Immunodeficiency and infection Flashcards
What is immunodeficiency?
Immune system can’t protect host from pathogens
Primary ID
Inherited/genetic or developmental defect in the immune system
Severe combined immunodeficiency
Primary ID, genetic defect leads to lack of functional T and B cells in blood
What are the four types of SCID
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
What is DiGeorge syndrome?
Deletion of chromosome 22 causes thymus defect, reduced development of parathyroid and congenital heart abnormalities due to T-box transcription
What is B cell immunodeficiency?
Decreased production of >1 AB isotope
Symptoms of B cell immunodeficiency
Complete absence of mature B cells/plasma cells
Suffer from recurrent infection but display normal response against virus and fungi - T cell unaffected
Bruton’s hypogammaglobulinaemia
X-linked Low conc of IgG, no other ABs No peripheral B cells Recurrent bacterial infections Defect in Bruton's tyrosine kinase
Leukocyte adhesion deficiency
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
Chronic granulomatous disease
X-linked or autosomal recessive
Neutrophils don’t make superoxide (NADPH oxidase) so can engulf bacteria but not kill
Complement deficiency
Failure to activate complement - increased susceptibility to bacteria
Symptoms of primary ID
Recurrent infections
Trouble gaining weight
Comorbid conditions (delayed cord cutting)
DDx PID
Acquired and non-immunological causes (CF)
Low IG due to loss of enteropathy, nephropathy or burns
HIV
Malnutrition (SID specific)
SCID emergency treatment
Isolation No live vaccines Ig therapy Enzyme replacement Haemopoetic stem cell transplantat
Acquired ID
External agents - drugs, immunosuppressants, corticosteroids, malnutrition
HIV
Sx acquired ID
Susceptible to common and opportunistic infections
HIV
Retrovirus of lentivirus genus
Infects and kills CD4
Uses integrate to incorporate into genome
<200 CD4 = AIDS
Diagnosis HIV
ELISA detects AB presence (gag p24)
PCR used in infants because of remnants from mum
Confirmed with western blot
ABs and HIV
Occur 6-12 weeks after exposure
When they are detected, the person is seroconverted or seropositive
AIDS diagnosis
HIV-1 in blood
<200 CD4
Impaired hypersensitivity
Opportunistic infections
HIV/AIDs treatment
HAART combines drugs from different classes
Antibiotics
Immunisation
