Hypersensitivity

-

Type
Mediators
Timing
Examples
Type I Hypersensitivity
Allergy
Exogenous antigen binding to IgE bound to Mast cells leading to degranulation
Within minutes to an hour, rarely delayed onset (10-12 hours)
Asthma
Anaphylaxis
Hayfever
Type II Hypersensitivity
Cytotoxic
Caused by endogenous antigens which bind to cells. Antibodies IgM and IgG bind to these cells causing apoptosis
Minutes to hours
Autoimmune haemolytic anaemia, thrombocytopenia, Goodpasture’s syndrome
Type III Hypersensitivity
Immune complex (autoimmune)
Caused by endogenous or exogenous antigens bound to IgG forming immune complexes which causes activation of the complement system and neutrophils causing systemic or organ specific damage.
3-8 hours
SLE, Aspergillosis, Rheumatoid arthritis,
Type IV Hypersensitivity
Delayed type
Caused by helper T cells and cytotoxic T cells which cause localized damage and recruits monocytes and macrophages.
48-72 hours
Contact dermatitis, Tuberculin test, granuloma in TB, toxoplasmosis

http://en.wikipedia.org/wiki/Hypersensitivity
http://pathmicro.med.sc.edu/ghaffar/hyper00.htm

Comments

Post a Comment

Popular posts from this blog

Pleural effusion

-
Image
Definition Pleural effusion is a collection of fluid in the pleural space between the visceral pleura surounding the lungs and the parietal pleural attatched to the throacic wall. Demographics Pleural effusions are relatively common, but it is a manifestation of other underlying diseases. The prevalence and incidence of pleural effusions is therefore dependent on it's cause. Pathophysiology/causes Pleural fluid is usually filtered from the parietal pleura into the pleural space, due to hydrostatic pressure from the capillaries, negative pressure in the pleural space and pleural oncotic pressure. The visceral pleura is perfused by the pulmonary system which has a lower pressure, and fluid in the pleural space is therefore drawn back in through the visceral pleura due to the higher oncotic pressure in plasma. Some of this fluid is then drained by the lymphatic system.
Read more

Diabetic Ketoacidosis (Adults)

-
Image
Definition : A major life threatening metabolic condition occurring in diabetic patients leading to hyperglycaemia , ketoacidosis , dehydration and ketonuria . Pathophysiology:  The lack of insulin primarily leads to hyperglycaemia and ketonaemia:  Insulin insufficiency leads to reduced uptake of glucose into cells and increased blood concentration of glucose.  As glucose are not taken into cells, alternative sources of energy are used.  Most cells break down fatty acids instead of glucose which forms ketones. Ketone levels therefore reflects the glucose deficit in cells.  Lack of insulin also leads to an increase in opposing hormones which lead to increased glycogenolysis, gluconeogenesis and lipolysis. 
Read more

Describing skin lesions

-
Image
Describing lesions  Site, Distribution and symmetry Type of lesion Size Shape - edges, well demarcated? regular/irregular shape? Surface -color and texture, scaly vs non-scaly (epidermis lesions are scaly) Special features - fluid filled?, mobility, temperature/inflammation, other features.
Read more