Simple Table: Comparing Antigen and Antibody Functions in Immunity
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 Antigen vs Antibody: What Sets Them Apart in Biology
1. What is the main difference between an antigen and an antibody?
The main difference is their role in the immune system. An antigen is a foreign substance, like a virus or bacterium, that enters the body and triggers an immune response. An antibody is a protein produced by the body's immune system specifically to identify and neutralise that antigen.
2. What exactly is an antigen and where is it found?
An antigen is any substance that your immune system recognizes as foreign or potentially harmful. They are typically proteins or large polysaccharides found on the surface of pathogens, such as:
- Bacteria
- Viruses
- Fungi
- Pollen or other allergens
- The cells of a transplanted organ
When these enter your body, they act as a signal for your immune system to launch a defense.
3. What is an antibody and how does the body make them?
An antibody, also known as an immunoglobulin (Ig), is a Y-shaped protein made by specialized white blood cells called B lymphocytes (or plasma cells). The body produces antibodies in response to detecting a specific antigen. Each antibody is custom-made to bind to one particular antigen, much like a key fits a specific lock.
4. How do antigens and antibodies interact to fight an infection?
The interaction is highly specific. The tips of the antibody's 'Y' shape have a unique structure called a paratope, which precisely fits a specific part of the antigen called an epitope. When an antibody binds to an antigen, it can neutralise the threat directly or 'tag' the pathogen, marking it for destruction by other immune cells.
5. How do antigens and antibodies determine a person's blood type?
Your blood type (A, B, AB, or O) is determined by the type of antigens present on the surface of your red blood cells. For example, Type A blood has A antigens, and Type B has B antigens. Your body naturally produces antibodies against the blood type antigens you *don't* have. This is why giving someone the wrong blood type during a transfusion causes a dangerous immune reaction.
6. What is the difference between an antigen test and an antibody test for a disease?
An antigen test checks for the presence of the antigen itself (e.g., parts of a virus), indicating a current, active infection. An antibody test checks for the presence of antibodies in your blood, which indicates that your body has mounted an immune response due to a past infection or vaccination.
7. Why can't the same antibody fight off different viruses, like the flu and a common cold?
The binding between an antibody and an antigen is incredibly specific due to their unique shapes. An antibody created to fight the influenza virus will not recognise the antigens on a common cold virus. This specificity ensures the immune response is targeted and efficient, but it also means your body must create new, unique antibodies for every different pathogen it encounters.
8. Can the body's own cells have antigens?
Yes, your body's cells have 'self-antigens' on their surface. Normally, your immune system recognizes these as friendly and does not attack them. However, in autoimmune diseases, the immune system mistakenly identifies these self-antigens as foreign and produces antibodies against them, leading to an attack on the body's own healthy tissues.
