Immunology and Infection Flashcards
What are helper T cells also known as?
CD4+ T cells
What are cytotoxic T cells also known as?
CD8+ T cells
What is the function of helper T cells?
Stimulation of the B-cells to plasma cells which produce antibodies
This process takes place in the lymph-nodes
What os the function of cytotoxic T-cells?
Destruction of viruses and fungi - through destruction of the intra-cellular organisms
What are the features of severe combined immunodeficiency disorder?
Tends to present before 3 months of age
Severe lymphopenia from birth
Severe decrease or absent immunoglobulins
No antibody response to vaccinations
No B cell function or T cell function - hence small thymus and no tonsils/ adenoids noted
Recurrent infections +/- pneumonia
Tx w. bone marrow transplant
What is the pathophysiology of x-linked agammaglobulinaemia?
Defect in B-lymphocyte development which is caused by a mutation in Bruton tyrosine kinase (BTK)
BTK is involved in signalling naive B-cells to become plasma cells which then become antibodies - hence a mutation in this means that B-cells remain naive and don’t become antibodies
What are the features of x-linked agammaglobulinaemia?
Only affects boys - presents after 6 months of life (after maternal antibodies have disappeared)
Tends to present with recurrent infections
Diagnosed by flow cytometry - shows no mature B-cells
No antibodies present (IgA, IgG, IgM, IgE)
Tx - IVIg (or subcutaneous Ig)
What is the pathophysiology of common variable immunoglobulin deficiency?
Lack of B-lymphocytes or plasma cells
What are the features of CVID?
Appears during adolescence - very rarely appears before 6 years
Low IgG and IgA - variable but no absent
Normal size of large tonsils - recurrent bacterial infections
Autoimmune complications - vitiligo, RA, AIHA
Tx - IVIg (or subcutaneous Ig)
What are the features of transient hypogammaglobulinaemia of infancy?
Presents between 6-12 months of age
Commonly associated with asthma and allergies
Normal response to vaccinations
Low IgG with or without low IgA and IgM
T cell immunity is intact
Tx - supportive
IVIg in severe cases
What are the features of selective IgA deficiency?
Defined as undetectable IgA less than 5
Most common immunodeficiency
Recurrent pneumonia is present - especially with encapsulated bacteria (strep, haemophilis, m. cataralis)
Dx - low or absent IgA
Tx - abx PRN
What is the structure of diphtheria?
Gram positive bacillus
aka Klebs-Loffler bacillus
What is the structure of chlamydia?
Gram negative bacterium
What is the treatment of chlamydia?
Doxycyline PO
Second line - erythromycin/ ofloxacin
What is the shape of strep. pneumonia?
Gram positive diplococci
What is the shape of h. influenzae?
Gran negative coccibacillus
Which antibiotic is given to pregnant women as bacterial meningitis prophylaxis?
Ciprofloxacin
What shape is group B strep?
Gram positive cocci
What shape is E.coli?
Gram negative, anaerobic, rod shaped bacteria
What shape is listeria?
Gram positive
What are the most common causes of bacterial meningitis in the first 4 weeks of life?
Group B strep (gram +ve cocci)
E. coli (gram negative bacilli)
Listeria (gram positive bacilli)
Which immunoglobulin is most associated with periodic fever syndrome?
IgD
How is chronic granulomatous disease diagnosed?
Dihydrorhodamine neutrophil burst assay (DHR)
What are the features of chronic granulomatous disease?
Frequent staph. aureus infections - most notably frequent skin abscesses
When should mast cell tryptase levels be tested?
Peak is at 2 hours
Levels rise after 30 minutes so should be tested at approx. 1-2 hours post reaction
What is the pathophysiology of XL Hyper-IgM syndrome?
Normally CD40 ligand is required to differentiate IgM into IgA, IgE and IgG - however in hyper-IgM syndrome there is a deficiency of CD40 therefore there is a build up of IgM and lack of other immunoglobulins
What are the features of XL hyper-IgM syndrome?
Frequent infections - specifically pneumonia or PJP
Diagnosis - High or normal IgM
Low IgA, IgG, IgE
Deficient CD40 ligand on activated CD4+ T-cell lymphocytes
Mx - Ig replacement
What are the features of hyper-IgE syndrome (aka Jobs syndrome)?
Recurrent infections
Coarse facial features
Eczema
Pneumatocele
Dx - elevated IgE (100 times higher than normal)
What are the features of Wiskott-Aldrich syndrome?
X-lined recessive therefore only affects boys
Mutation of WASp
Triad of eczema, recurrent infections (due to absent T-cells) and thrombocytopenia
Increased risk of lymphoma (EBV related) and leukaemia
What is the pathophysiology of leukocyte adhesion deficiency?
The leukocyte cannot migrate to the site of the infection due to a lack of integrin CD18 subunit which would normally adhere to the leukocyte molecule and the cellular adhesion molecules passing it to the site of infection
Infection without pus
What are the clinical features of leukocyte adhesion defect?
Delayed umbilical cord seperation >2 months
No pus present at the site of the wound
Poor wound healing
Persistent leucocytosis - raised leucocyte count
What is the investigation of choice for leukocyte adhesion defects?
Flow cytometric measurements of surface glycoproteins (CD18 and CD11)
What is the pathophysiology of Chediak-Higashi syndrome?
It is a protein trafficking defect which means there is a deficiency of the protein involved in moving phagocytes to the lysosomes meaning impaired phase-lysosomal function
What are the features of Chediak-Higashi syndrome?
Partial oculocutaneous albinism
Photophobia
Bleeding diathesis (due to low platelets)
Peripheral neuropathy
Recurrent infections
What is the pathophysiology of chronic granulomatous disease?
NADPH oxidase deficiency - meaning that phagocytic cells are unable to generate hydrogen peroxide or hydroxyl radicals meaning that PMNs are unable to kill the bacteria
What are the features of chronic granulomatous disease?
Pyogenic infections - abscess formation in different sites
Failure to thrive
Formation of granulomas
How is chronic granulomatous disease diagnosed?
Neutrophil oxidative burst test - using rhodamine die
What is the pathophysiology of hereditary angioedema?
Type 1 HAE occurs due to a deficiency of C1 esterase inhibitor
Type 2 HAE occurs due to defective C1 esterase inhibitor
What are the most common causes of infective endocarditis in diabetic and immunocompromised patients?
Haemophilus
Actinobacilus
Cardiobacterium
Eikenella
Kingella
What are the most common causes of infective endocarditis?
In order from most common:
Staphylococcus Aureus
Coagulase negative Staphylococcus (more likely in patients with prosthetic material) - e.g. staph. epidermidis
Streptococcus viridans
Describe the differing hypersensitivity reactions?
Acute - type 1
Cytotoxic - type 2 (hours to days) - type 2
Immune mediated (weeks) - type 3
Delayed - type 4
What is the management of HIV in children who are positive?
Antiretroviral therapy should be started in any child with a diagnosis of HIV regardless of their viral load and CD4 count
What is the management of HIV in neonates born to HIV positive mothers?
Anti-retroviral Tx within 72 hours of birth (ideally within 12 hours)
Low risk - should start zidovudine for 4 weeks
High risk - should start combination ART (zidovudine, lamivudine, nevirapine)
What is the treatment of choice malaria in the paediatric population?
Malarone (Proguanil with atovaquone)
What is the transmission of hepatitis?
Hep A - contaminated water, i.e. faecal oral transmission
Hep B - vertical/ blood contact/ body fluids
Hep C - Blood
Hep D - vertical/ blood/ body fluids - requires patient to already be infected with Hep B.
Hep E - contaminated water, i.e. faecal oral transmission
What are the characteristic findings of typhoid?
Relative bradycardia and fever
Discuss complement activation by immunoglobulins?
IgA - alternative
IgG + IgM - classical
IgE + IgD - cannot activate complement
What is the treatment of chlamydia?
Macrolides - e.g erythromycin
Which strains of HPV are most commonly associated with neoplasm?
HPV 16 and 18
What is the treatment of choice for syphilis?
Benzylpenicillin
What is the treatment of choice for Gonorrhoea?
Ceftriaxone
