Dr. Tola FARAJ/Lecturer_____________________________________________

Immunology_ 2nd Stage/2nd Semester

tola.faraj@tiu.edu.iq

https://tiu.edu.iq/

2020 - 2021

TIU - Faculty of Science

Medical Analysis Department

Antibody

Theory

Lecture Outlines: 1h

5 minutes all settle in the hall, with

attendance

5 minutes Quiz

Clarification through ppt slides

Open discussion

Asking questions

Participation

For any extra question from the

student’s side please do email me on:

tola.faraj@tiu.edu.iq

Antibodies are globulin proteins

(immunoglobulins) that are synthesized in serum and tissue fluids, which react specifically with the antigen that stimulated their production.

The most important function of antibodies is to confer protection against microbial pathogens.

Antibodies confer protection in thefollowing ways:

1. They prevent attachment ofmicrobes to mucosal surfaces ofthe host.

2. They reduce virulence of microbesby neutralizing (deactivating) toxinsand viruses.

3. They facilitate phagocytosis byopsonization of microbes.

4. They activate complement, leadingto complement-mediated activitiesagainst microbes.

OPSONIZATION The process whereby opsonins make an invading microorganismmore susceptible to phagocytosis.

OPSONIN An antibody or complement protein that enhances phagocytosis bymarking an antigen.

Major opsonins are:1.Immunoglobulin (Ig)G antibodies2.Certain plasma lectin MANNOSE BINDING LECTIN3.C3b and it’s cleavage products e.g. iC3b (inactive C3b)

Opson in ancient Greece referred to the delicious side-dish of any meal.

Complement is a system of plasma proteins that

can be activated directly by pathogens or indirectly bypathogen-bound antibody, leading to a cascade ofreactions that occurs on the surface of pathogens andgenerates active components with various effectorfunctions.

Complement system is covered by nine centralcomponents of the cascade (C1 to C9), multiple activationproducts (such as C3a and C3b), regulators and inhibitors(e.g. Factor H and C4BP), proteases and newly assembledenzymes (e.g. C4b2a and Factor B), or effector moleculereceptors (such as C3aR and C5aR).

The main function of complementproteins is to:

1aid in the destruction of pathogens bypiercing their outer membranes (cell lysis)or;

2by making them more attractive tophagocytic cells such as macrophages (aprocess known as opsonization).

tola.faraj@tiu.edu.iq

Thanks