Disorders Autoantigens
Glomerulonephritis Kidney cell antigens that resemble
Streptococcus bacteria antigens.
Graves’ disease Thyroid gland antigens near thyroid
stimulating hormone receptor, caus-
ing over activity.
Juvenile diabetes Pancreatic beta cells.
Haemolytic anaemia Red blood cell membrane.
Myasthenia gravis Receptors for nerve messages on
skeletal muscle (acetylcholine receptor).
Pernicious anaemia Binding site for vitamin B 12 on
cells lining stomach.
Rheumatic fever Heart cell antigens that resemble
Streptococcus bacteria antigens.
Rheumatoid arthritis Cells lining joints.
Scleroderma Connective tissue cells.
Systemic lupus
erythematosus (SLE)Heart, joints, nervous system, blood
vessels.
Ulcerative colitis Colon cells.Hypersensitivity (Allergy)
• Hypersensitivity or allergy is the excessive immune
response to common antigens, called allergens.
• Allergy is due to the release of chemicals like
histamine and serotonin from the mast cells.
• Common examples of allergens are mites in dust,
pollens, animal dander, etc.
• Symptoms of allergic reactions include sneezing, watery
eyes, running nose and difficulty in breathing.
• The use of drugs such as antihistamines, adrenalin and
steroids quickly reduce the symptoms of allergy.
• Common examples of allergy are hay fever and
asthma.
• Hay fever is the form of allergy due to pollen of
grasses, trees and other plants. It is characterized by
inflammation of the membrane lining the nose and
sometimes of the conjunctiva.
• In asthma, the tissues surrounding the bronchioles
of the lungs swell up, and compress the bronchioles.
Hence, there is difficulty in breathing.
types of hypersensitivity reaction
• They are divided into four classes (Type I-IV) based
on the mechanisms involved and the time course of
hypersensitive reaction.
• Type I hypersensitivity is an immediate or
anaphylactic reaction, often associated with allergy.
Symptoms can range from mild discomfort to
death. It is mediated by IgE, mast cells and
basophils.
• Type II hypersensitivity occurs when antibodies bind
to antigens on the patient’s own cells marking them
for destruction. This is also called antibody-dependent
(or cytotoxic) hypersensitivity, and is mediated by
IgG and IgM antibodies.
• Type III hypersensitivity involves circulating antigen-
antibody immune complexes that collect in various
tissues and post capillary venules, with subsequent
complement fixation.
• Type IV hypersensitivity (also known as cell
mediated or delayed type hypersensitivity) usually
takes two to three days to develop. Type IV reactions
are involved in many autoimmune and infectious
diseases, but may also involve contact dermatitis
(poison ivy). These reactions are mediated by
T cells, monocytes and macrophages.
• Anaphylaxis (anaphylactic shock) : It is an
allergic reaction involving all the tissues of the body
and occurs in a few minutes after the injection of
an antigen such as penicillin. Such a reaction is
very serious.
• Histamine released from ruptured mast cells causes
marked dilation of all the arteries so that a large
amount of fluid is passed from the blood to the tissues
and there is a drastic fall in blood pressure.
vACCInAtIon And ImmunIsAtIon
• Vaccine (L. vacca = cow) is a preparation/suspension
or extract of dead/attenuated (weakened) germs of a
disease which on inoculation (injection) into a healthy
person provides temporary/permanent active/passive
immunity by inducing antibodies formation.
• The process of introduction of vaccine into an
individual to provide protection against a disease is
called vaccination.
• In vaccination, a preparation of antigenic proteins
of pathogens or inactivated/weakened pathogens
(vaccine) is introduced into the body.
• These antigens generate the primary immune
response, and the memory B and T cells.
• When the vaccinated person is attacked by the same
pathogen, the existing memory T or B cells recognise
the antigen quickly and attack the invaders with a
massive production of lymphocytes and antibodies.Table : Autoimmune disorders and their
autoantigens