Inflammatory reactions
• Inflammation is a defensive response of the body to
tissue damage.
• The conditions that may produce inflammation are
pathogens, abrasions, chemical irritations and extreme
temperature.
• Inflammatory reaction causes redness, heat, swelling,
and pain in the area of infection.
• Redness and heat are due to capillary dilation
resulting in increased blood flow.
• Swelling is caused by the passage of plasma from
the blood stream into the damaged tissue.
• The pain is mainly due to the tissue destruction, and
to a lesser extent, due to the swelling.
• Inflammation is localised to area of infection/tissue
injury by release of substances from microorganisms
or chemicals (chemical mediators) released from cells
in tissues, e.g., histamine from mast cells. Once micro
organisms are destroyed, inflammation subsides.
fever
• Fever is often the result of infection and is caused
by release of chemicals (pyrogens) from damaged
tissues and the cells involved in inflammation.
Interferons
• Interferons are glycoproteins released by living cells in
response to viral attack, and make the surrounding cells
resistant to viral infection by inhibiting multiplication
of viral particles.
• Interferons are divided into three groups based on the
cell of origin, namely leucocyte (alpha interferon),
fibroblast (beta interferon) and lymphocyte
(gamma interferon).
• They are cytokine (chemical mediators) barriers.
Complement system
• Complement system is a biochemical cascade consisting
of 30 different serum proteins which participate in both
innate and acquired immunity.
• It is of two types : classical and alternate or properdin
pathway.
• Classical pathway operates in acquired immunity
and becomes active in response to antigen-antibody
complex.
• Alternative pathway or properdin system
operates in innate immunity, and is activated directly
by the presence of bacterial endotoxins, and other
components of invading microorganisms.
Acquired immunity/specific defence
mechanism (third line of defence)
• If a pathogen is able to get past the body’s non-
specific defences, the immune system reacts with a
series of specific defences that attack the disease
causing agent.
• Response of the immune system to specific pathogens
is called specific defence, and it is the third line
of defence developed by an animal in response to
disease causing microbes.
• This occurs by making specialized cells and antibodies
that make the pathogen harmless.Cells involved in acquired immunity
• The cells of the adaptive immune system are special
types of leucocytes, called lymphocytes and antigen
presenting cells (APCs).
• B-lymphocytes or B-cells and T-lymphocytes or T-cells
are the major types of lymphocytes that are derived
from hematopoietic stem cells in the bone marrow.
• B-cells are involved in the humoral immune response,
whereas T-cells are involved in cell-mediated immune
response.