[Biology Class Notes] on Difference Between Antigen and Antibody Pdf

Antigens are large molecules of proteins, present on the surface of the pathogen, like bacteria, fungi viruses, and other foreign particles. When these harmful agents enter the body, it induces an immune reaction within the body for the assembly of antibodies.

For Example: When a standard cold virus enters the body, it causes the body to supply antibodies to stop from getting sick.

Properties of Antigens

The properties of antigens are as follows:

• The antigen should be a far off substance to induce an immune reaction .

• The antigens have a molecular mass of 14,000 – 6,00,000 Da.

• They are mainly proteins and polysaccharides.

• The more chemically complex they are, the more immunogenic they will be.

• Antigens are species-specific.

• Age influences immunogenicity. Very young and really old people exhibit very low immunogenicity.

Types of Antigens

On the Basis of Origin

There are different types of antigens on the idea of origin:

Exogenous Antigens

These are the antigens that have entered the body from outside, for example, inhalation, injection, etc. These are the foremost common sorts of antigens and include pollens and food that cause allergies.

Endogenous Antigens

Endogenous antigens are people who are generated within the traditional cells thanks to viral or intracellular bacterial infections.

Autoantigens

Autoantigens are normal proteins or a posh of proteins or macromolecules that’s attacked by a system causing autoimmune diseases.

Tumour Antigens

It is an antigenic substance produced in tumour cells that induces an immune reaction within the host. These are presented by MHC-I and MHC-II on the surface of tumour cells.

Native Antigens

A native antigen is the one that’s not processed by an antigen-presenting cell.

On the Basis of Immune Response

On the idea of the immune reaction , antigens are often classified as:

Immunogen

These could also be proteins or polysaccharides and may generate an immune reaction on their own.

Hapten

These are non-protein, foreign substances that need a carrier molecule to induce an immune reaction .

Antibodies aren’t found at an area intrinsically, but whenever our system encounters antigen of a pathogen, B cells get activated immediately releasing antibodies into the bloodstream. These immunoglobulins undergo mitosis leading to cellular division and continuously produce antibodies as a result of producing more cells. These antibodies remain within the blood for a few times but B cells remember these antigens and repeat an equivalent course of action whenever they reappear in our body.

What are Antibodies?

Antibody (Ab) is also known as an immunoglobulin(Ig). These are big in size, Y-shaped blood proteins produced by plasma cells. They bind to foreign particles and invade them. Antigens are foreign pathogens that invade the body and have the potential to offer rise to a response from our immunity system either by grouping up with a bigger molecule or alone after binding with antibodies for a specific immune reaction. Hence, antigens stimulate the assembly of antibodies by the system.

Antibody Structure

An antibody structure consists of a Y-shaped molecule composed of 4 polypeptide subunits. The N-terminus of the heavy chains associates with one of the light chains and forms two antigen binding domains. These form the arms of the “Y” shape and are referred to as fragment antigen binding (Fab) domains. It helps within the antibody’s interaction with the effector cells.

All four polypeptide subunits are held together by disulfide and non-covalent bonds.

The large chains of the antibodies contain a variable region and three constant regions. Each antibody has two identical antigen-binding sites and they differ within the antibodies.

Difference Between Antigen and Antibody