What Is the Difference Between Antigen and Antibody in Structure and Function
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 in Immunology
1. What is the difference between antigen and antibody?
The main difference between an antigen and an antibody is that an antigen is a foreign substance that triggers an immune response, while an antibody is a protein produced by the immune system to specifically recognize and bind that antigen.
- An antigen can be a protein, polysaccharide, or toxin present on pathogens like bacteria and viruses.
- An antibody (also called immunoglobulin) is produced by B lymphocytes in response to a specific antigen.
- Antigens initiate the immune response, whereas antibodies help neutralize or destroy the antigen.
2. What is an antigen in biology?
An antigen is any foreign molecule that is recognized by the immune system and can trigger an immune response.
- Antigens are commonly found on the surface of pathogens such as bacteria, viruses, fungi, and parasites.
- They are usually proteins or polysaccharides.
- Specific regions on antigens called epitopes are recognized by antibodies or immune cells.
3. What is an antibody and what is its function?
An antibody is a Y-shaped protein produced by B cells that specifically binds to a particular antigen to help eliminate it from the body.
- Antibodies are also known as immunoglobulins (Ig).
- They bind to specific epitopes on antigens.
- Functions include neutralization of toxins, agglutination of pathogens, and activation of the complement system.
4. How do antigens and antibodies interact?
Antigens and antibodies interact through a highly specific binding between the antigen’s epitope and the antibody’s binding site.
- The binding site is located in the variable region of the antibody.
- This interaction forms an antigen-antibody complex.
- The complex can lead to pathogen neutralization, opsonization, or destruction by immune cells.
5. What are examples of antigens and antibodies?
Examples of antigens include viral surface proteins and bacterial toxins, while examples of antibodies include IgG and IgM immunoglobulins.
- Antigen example: Spike protein of the SARS-CoV-2 virus.
- Antigen example: Tetanus toxin produced by Clostridium tetani.
- Antibody example: IgG found in blood plasma.
- Antibody example: IgA present in saliva and breast milk.
6. Are antigens always harmful to the body?
Antigens are not always harmful, but they are substances recognized as foreign by the immune system.
- Many antigens come from harmful pathogens like bacteria and viruses.
- Some antigens are harmless substances such as pollen, which may cause allergic reactions.
- Even transplanted organs can act as antigens and trigger an immune response.
7. Where are antibodies produced in the body?
Antibodies are produced by plasma cells, which are activated forms of B lymphocytes.
- B cells are formed and mature in the bone marrow.
- After encountering a specific antigen, B cells differentiate into plasma cells.
- Plasma cells secrete large amounts of specific antibodies into the blood and lymph.
8. What is the structure of an antibody?
An antibody has a Y-shaped structure composed of two heavy chains and two light chains linked by disulfide bonds.
- The arms of the Y contain the variable regions that bind to antigens.
- The stem region is called the constant region, which determines the antibody class.
- The two antigen-binding sites allow antibodies to bind two identical epitopes.
9. What are the main types of antibodies?
The five main types of antibodies are IgG, IgA, IgM, IgE, and IgD, each with a specific role in immunity.
- IgG: Most abundant in blood and provides long-term protection.
- IgA: Found in body secretions like saliva and tears.
- IgM: First antibody produced during an initial infection.
- IgE: Involved in allergic reactions and defense against parasites.
- IgD: Functions mainly as a receptor on B cells.
10. Why are antigens and antibodies important in immunity?
Antigens and antibodies are essential for adaptive immunity because antigens trigger the immune response and antibodies specifically target and eliminate those antigens.
- Recognition of antigens allows the immune system to distinguish self from non-self.
- Antibodies provide specific and long-lasting protection.
- This interaction forms the basis of vaccination and immune memory.
