Food allergies are related to specific defenses or specific immunity.
Immune literary means “free of burden”.
Actions of the immune system are triggered by antigens (foreign substances).
Most antigens are large protein molecules ; Some antigens are polysaccharides and few are glycoproteins (carbohydrate and protein) or nucleo-proteins .
Specific Immunity Immunity Innate (inborn) Genetic factors Acquired Active (own Ab) Passive (Ready-made-Ab) Natural (Exposure to Foreign Agents) Artificial (immunization) Natural Maternal Ab Ab = Antibodies Artificial (Ab from Other sources)
Primary and secondary responses to an antigen Primary response : first response when host’s B-cell recognize the antigen Secondary response : upon second exposure to the antigen, the Memory cells will divide, thus make more of the total antibody
Nature of IgE Allergic Reactions Antigen + IgE + Mast cells = Mediator release Mediators= histamine and others Picture credit: from Dr. Gary E. Kaiser http://www.cat.cc.md.us/courses/bio141/lecguide/index.html
What is Histamine? Histamine triggers the inflammatory response . Histamine is produced by basophils ( a type of white blood cell) and by mast cells ( a resident cell in tissues of the body; present more in skin, lungs, eyes, digestive tract, mouth, nose and conjunctiva) in response to antigens. Found in almost all animal body cells, histamine increases the permeability of the capillaries to white blood cells and other proteins, in order to allow them to engage foreign invaders in the affected tissues.
Recognise antigens on surface of leukocytes, especially macrophages
Enlagre and form a clone of T-helper cells
Secrete interferon and cytokines which stimulate B-cells and stimulate killer -cells
Can be infected by HIV
Also called cytotoxic
Destroy abnormal body cells, e.g. virus infected or cancer cells
Stimulated by cytokines (THcells)
Release perforin , which forms pores in target cells. This allows water and ions in = lysis
Control the immune system when the antigen /pathogen has
Only recently discovered so
little is known about them
Can survive a long time and give lifelong immunity from infection
Can stimulate memory B-cells to produce antibodies
Can trigger production of killer T cells
Mature in Thymus, which is most active just before and after birth. The thymus starts to shrink during puberty.
How T-cells work… Abnormal cell e.g cancer cell, infected cell Normal cell Antigen Killer T-cell recognises antigen Clones of killer T-cell attach to antigen Helper T-cell stimulates correct killer T-cell to multiply Killer T-cells release perforin pores Abnormal cell gains water, swells and bursts Helper T-cell also stimulates B-cells to make antibodies Memory T-cells stay in circulation Suppressor T-cells turn off immune response X X X
A. Sensitization: initial meeting of an allergen and the immune system that results in IgE production!
B. Activation of mast cells
IgE : is specific for a particular allergen that triggers the allergic reaction. The allergen binds to the immunoglobulin on specific immune cells called basophils and mast cells. This binding results in the release of chemicals that cause inflammation in the body, such as histamine, within 30 minutes of exposure. These chemical mediators cause allergy symptoms, such as urticaria (hives), runny nose, watery eyes, sneezing, wheezing and itching.
Anaphylaxis Potential fatal reaction to a food allergen causing reduced oxygen supply to the heart and other body tissues. Symptoms include: difficult breathing, low blood pressure, pale skin, a weak rapid pulse, loss of consciousness, death.
Food protein proctocolitis/ proctitis (inflammation of rectum)
Rectum is the final portion of large intestine. It empties stools from body through anus
Food protein-induced enteropathy : Celiac disease , an adverse immune response to the protein gluten.
Milk-soy protein intolerance (MSPI): non-IgE mediated allergic response to milk and/or soy protein during infancy and early childhood. Symptoms of MSPI are usually attributable to food protein proctocolitis or FPIES.
Heiner syndrome - lung disease due to formation of milk protein/IgG antibody immune complexes (milk precipitins) in the blood stream after it is absorbed from the GI tract. The lung disease commonly causes bleeding into the lungs and results in pulmonary hemosiderosis.
A strong desire to avoid a particular food Food Aversion Adverse reaction to food that does not involve the immune system Food Intolerance
Laboratory test are performed to look if the patients has IgE against specific types of food
It is a radioimmunoassay test
A person who has outgrown an allergy may still have a positive IgE years after exposure.
The suspected allergen is bound to an insoluble material and the patient's serum is added. If the serum contains antibodies to the allergen, those antibodies will bind to the allergen. Radiolabeled anti-human IgE antibody is added where it binds to those IgE antibodies already bound to the insoluble material. The unbound anti-human IgE antibodies are washed away. The amount of radioactivity is proportional to the serum IgE for the allergen.