The complement system is part of the innate immune system that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells. It was discovered in 1895 and consists of over 30 proteins produced by the liver and found in blood serum and tissues. Complement functions to defend against bacterial infections by enhancing phagocytosis, chemotaxis, and inflammation. It also bridges innate and adaptive immunity by augmenting antibody responses and enhancing immunological memory, and helps dispose of and clear dead host cells.

1. Dr. P. Saranraj M.Sc., M.Phil., Ph.D., NET
Assistant Professor
Department of Microbiology
Sacred Heart College (Autonomous)
Tirupattur, Vellore District.
Mobile: 9994146964
E.mail: microsaranraj@gmail.com
COMPLEMENT
SYSTEM

2. COMPLEMENT
Complement system is a part of the immune system that
enhances the ability of Antibodies and Phagocytic
cells to clear microbes and damaged cells from an organism
and promotes inflammation.
It is part of the Innate immune system.
The Complement was first discovered by Jules Bordet in
1895. He established that the Immune Bacteriolysis and
Haemolysis require two factors (i) Heat Stable Antibodies
and Heat Labile Component (at 55 °C) – Alexine.
The term Alexine was renamed as “Complement” which was
coined by Paul Ehrlich.

3. The Complement system consisting of over 30 proteins
produced by the liver and found circulating in
blood serum and within tissues throughout the body.
Complement is Heat Labile in nature.
The Complement does not binds with free Antigen or Free
Antibody. It can binds only with the Antigen – Antibody
Complex.
The Immunoglobulin IgG helps the Immune system to
trigger the Complement system.

4. Functions of Complement
1) Defending against bacterial infections by
enhancing Phagocytosis through
a) Opsonization - Microorganisms or other particles are coated
by serum components thereby preparing them for
recognition and ingestion by phagocytic cells.
b) Chemotaxis – Movement of cell towards food and away
from toxic materials.
c) Inflammation - A localized reaction that produces redness,
warmth, swelling, and pain as a result of infection, irritation,
or injury.
c)Activation of Leucocytes (WBC)
d) Lysis of Bacterial cell wall and results in Apoptosis (Cell
Death)

5. 2) Bridging Innate immunity and Adaptive immunity
by
a) Augmentation (the action or process of making greater in
size or amount) ofAntibody responses
b) Enhancement of Immunologic memory (the ability of
the immune system to respond more rapidly and effectively
to a pathogen that has been encountered previously).
3) Disposing and clearance of dead host cells

6. 2) Bridging Innate immunity and Adaptive immunity
by
a) Augmentation (the action or process of making greater in
size or amount) ofAntibody responses
b) Enhancement of Immunologic memory (the ability of
the immune system to respond more rapidly and effectively
to a pathogen that has been encountered previously).
3) Disposing and clearance of dead host cells