Type/Cause Identification Problems, Aetiology, Diagnosis, Phagocytic dysfunction, Complement Deficiencies, B lymphocyte defects/deficiencies, T lymphocyte defects/deficiencies, Combined B and T cell deficiencies, Acquired deficiency,
Type/Cause Identification Problems
● Different cells, antibodies, can have similar reactions
● Everyone has a different ‘normal’ value
● Some components difficult to measure unless with specialist kits
Aetiology
● Most congenital immunodeficiencies arise from de novo mutations (acquired) but some are
inherited
● primary/congenital
○ Usually inherited. Symptoms masked for first few months as baby due to placental and
breast milk antibodies
○ Degree of deficiency depends on the style of maturation affected. The earlier it develops
the worse the outcome. Eg Digeorge syndrome during foetal development is severe
○ In evolutionary terms congenital deficiencies are not beneficial so are relatively rare
○ Can affect myeloid and/or lymphoid lineage
● secondary/acquired
○ Causes include infectious diseases, cancer, stress, malnutrition, immunosuppressive drugs
Diagnosis
● Symptoms are a good starting point for diagnosis but there is a lot of overlap. Eg low phagocyte
numbers, complement deficiencies, low antibody count from recurrent bacterial infections
(humoral response), persistent fungal/protozoan infections (cell mediated immune response)
● WHO classifications
○ Phagocyte dysfunction. With either endothelial adhesion, chemokines, or ingestion
○ Complement abnormalities/deficiencies. C3 convertase is pivotal
○ B lymphocyte defects/deficiencies. Antibody lacking, dysactivation, APCs
○ T lymphocyte defects/deficiencies. T helper cell problems cause lack of antibodies,
misleading to B cell deficiency
○ Combined B and T cell defects/deficiencies. Sufferers must live in confined, sterile place
Phagocytic dysfunction
● Low neutrophil numbers caused by defective production during haemopoiesis. Most vulnerable
during 0-12 months. Treatment available through colony-stimulating factors or recombinant
granulocytes
● Leucocyte adhesion deficiency causes inability of neutrophils to ‘stick’ to capillary endothelium,
preventing them migrating to the inflammatory site.
○ Leucocyte function associated antigen (LFA-1) is an important adhesion molecule LFA
is made up of an α and β chain. A deficiency in either one leads to a defective LFA-1..
Eg if β chain is defective then CR3 cannot bind and cannot act as an opsonin.
○ Life expectancy for LAD varies from childhood to middle age
○ LAD prevents phagocytes from entering infection site and leads to necrotic ulcers in its
place.
○ Treatment is only antibiotics as neutrophils have too short a half life to be transfused
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