What are antigens?
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
FAQs on Difference Between Antigen and Antibody
1. What are antigens?
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.
2. What are the 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.
3. How can you tell which type of antigen you are dealing with?
Antigens can be classified into three types:
An antigen may be exogenous (from outside the host immune system), endogenous (produced by intracellular bacteria and viruses replicating inside the host cell), or autoantigens (produced by the host). A sensitized immune system will mount an attack on autoantigens, resulting in an autoimmune disease. In normal situations, autoantigens do not elicit an immune response. Allergies are a common term for autoantigens present in the body.
4. How can antigens be described?
Antigens specific to Blood Groups: The antigens of red blood cells are perhaps among the most familiar to most people. Antigens are proteins and sugars that form a protective coating on blood cells. Antigens A, B, and O are sugars, also known as glycoproteins or glycans. A protein called Rh antigen, which is either present (+) or absent (-), is present or absent in the body. By combining these antigens, one is able to determine the blood type (e.g., O+, AB+, B-, and so on).
Antigens associated with Influenza: Since the influenza virus has a high mutation rate, it poses a particular health risk to the public. The influenza virus is coated with glycoproteins known as hemagglutinin and neuraminidase, which act as antigens. Antigenic drift allows viruses to evade detection by antibodies because the hemagglutinin antigen can undergo rapid changes.
Immunity: Antigens and antibodies are an integral part of any article about them. As part of the immune system, antibodies form the shape of a Y. The "arms" refer to the portion of the antigen that binds at its epitope and is the part that forms the paratope. This interaction is influenced not only by the amino acids at the back of the antibody but also by the shape and structure of the part of the antibody in contact. There is a possibility that the antigen that binds to the antibody does not have a straight line of amino acids but has angles and folds.
5. Can viruses be considered antigens?
Antigens are substances produced by viruses that cause their hosts' immune system to respond. An antigen in a viral protein will be detected by an immune response that is specific to that antigen in the viral genome.
An RNA or DNA genome is attached to a protein within a virus. Viruses lack cellular structure as well as metabolic functions independent of host cells. The replicating virus uses information in the viral genome to exploit the living cells.
Virion is another term for a mature virus particle. Each virus particle has two or three major components. These components are mentioned below:
The DNA or RNA sequences of an organism, whether double-stranded or single-stranded, linear or circular, and sometimes segmental. A single strand of nucleic acid can exhibit plus or minus polarity.
An enveloped nucleic acid containing proteins coded by the virus, which determines the virus' antigenicity. The enveloped nucleic acid can exhibit rotational, helical, or complex symmetry and consists of subunits called capsids.
A membrane surrounds the capsid in some cases and originates from the cellular membranes.
