Antibodies Role Of Antibodies

May 15, 2023, 16:45 IST

Our bodies produce antibodies in response to illness and immunisation. They help shield us from other infections and keep us from getting sick. Before the vaccination campaign, the proportion of individuals who tested positive for antibodies provided a reliable indicator of prior SARS-CoV2 virus infection. Since the beginning of 2021, many patients have tested positive for antibodies after receiving their first vaccine dosage.

Like every virus, SARS CoV-2 comprises two essential components: genetic material (RNA) and proteins. The immune system responds to the virus and prevents sickness by recognising the antigens and proteins on the virus' surface.

The immune system has various components that defend against viruses. The human immune system may recognise a viral antigen from a previous infection. In this case, immune cells called "B cells" will generate antibodies that attach to the virus and instruct other immune system cells to eradicate it.

The "adaptive immune system," composed of B and T cells, remembers prior infections and controls this detection. T cells instruct others to fight the virus and help B cells make antibodies and other immunological defences.

Because each infection results in T and B cells specially adapted to that infection, it is called adaptive immunity.

This article will explain how these antibodies are generated and coordinate with other immune system components to effectively defend against pathogens.

Antibodies and Immunity

Antibodies are proteins created by the immune system in reaction to the body's exposure to pathogens like viruses, bacteria, or toxins. Specific targets on these invaders are recognised by antibodies and bound to them, designating them for eradication and neutralisation. The body's defence against illness and infection depends heavily on antibodies.

The ability of the body to ward off illnesses is known as immunity. People are exposed to pathogens, such as viruses and bacteria, that cause disease daily. Antigens on the surfaces of pathogens trigger the immune system's response. The immunological response is the term used to describe the body's defence against antigens and for overall protection.

• Innate Immunity

A person is born with innate immunity, which includes physical barriers like skin and body hair, defence mechanisms like saliva and stomach acid, and general immunological responses like inflammation. Immunity of this kind is regarded as non-specific. The immune system can react fast to protect against any infection, even when unaware of the precise type of antigen attacking the body.

• Passive Immunity

Passive immunity is the term used to describe the body's capacity to combat disease by "borrowing" antibodies. For example, immunoglobulin, a blood component that contains antibodies, may be transfused from one person to another and can transfer antibodies to a baby through breast milk. The mother is the primary source of passive immunity in a newborn. During the final few months of pregnancy, the placenta allows antibodies to be delivered from mother to kid. Because of this, a child born at term will have the same antibodies as her mother. These antibodies can protect a baby from infections for up to a year by defending against specific antigens. Passive immunity is only effective when the antibodies exist since the body has not produced them.

• Active Immunity

The immunity that arises from immunological memory is acquired (adaptive) immunity. The body gets exposed to a particular antigen (added to a pathogen) and produces antibodies to that particular antigen. The body remembers the exact antigen and has antibodies to defend itself against it the next time it invades. A person may gain immunity after exposure to an infection, which causes them to contract a disease. When a vaccine replicates a particular pathogen, it can also result in acquired immunity since the vaccinated person develops an immune response without becoming ill.

Various Antibodies And Their Functions

• IgM

This family of immunoglobulins is the first to be created in response to infection. It is either present on the B cell membranes or as a 5-subunit macromolecule released by plasma cells. In addition, it is the first immunoglobulin class that newborns produce. In its Fc region, surface IgM varies from secretory form. Instead of binding to the IgM Fc receptor, surface IgM binds as an integral membrane protein. Multiple immunoglobulins are connected with disulfide linkages to form the pentameric protein called secreted IgM. This structure offers several binding sites. There are two light chains and two heavy chains in each monomer. IgM is especially well-suited for generating agglutination and complement activation because of its pentameric structure. The half-life of IgM is around 5 days.

• IgG

With up to 80% of all serum antibodies in this class, blood contains most of them. It exists only as monomers. IgG1>IgG2>IgG3>IgG4 are the four subclasses of IgG, and the subclass created depends on the kind of cytokine present.

IgG2 and IgG4 have extremely low and intermediate affinities for the Fc receptors on phagocytes, whereas IgG1 and IgG3 have strong affinities. IgGs can leave the bloodstream and penetrate tissues. IgG1, IgG3, and IgG4 can pass the placental barrier to protect babies. IgGs are highly effective at opsonising phagocytes through their Fc receptors and activating the complement system.

• IgA

Low quantities of monomeric IgA are seen in the blood. They are found in the dimeric form at mucosal surfaces, where they are most active and serve as the main line of defence. Mucosal linings produce more IgA than any other kind of antibody put together. It primarily serves as a neutralising antibody. Saliva, tears, and breast milk all contain high quantities of IgA. There are two IgA subtypes known to occur in humans, however, there is only one kind known to exist in mice. Up to 85% of the total IgA in serum may be found in IgA1. Selective IgA deficiency is one of the most prevalent immunodeficiency conditions that makes people more susceptible to infections.

• IgD

Found on the surface of most B lymphocytes, it is a monomeric antibody with two epitope binding sites. Its exact role is still unclear. However, it may be an antigen receptor necessary for B cell activation. Additionally, it has been suggested that IgD binds to mast cells and basophils, activating them to generate antimicrobial substances. It is also thought to contribute to the eradication of self-reactive autoantibody-producing B cells. IgD is also synthesised in a secreted form with two heavy chains of the class and two light chains and is present in trace amounts in serum. The half-life of IgD is around 3 days.

• IgE

These antibodies work well on mucosal surfaces, in blood, and in tissues. It exists as a monomer comprising two light chains and two heavy chains. Four Ig-like constant domains are present in the chain. It makes up approximately 0.002% of all serum antibodies and is only seen in trace amounts. The Fc region of most IgE is strongly linked to its receptors on mast cells and basophils. It is a critical component of hypersensitive reactions, and cytokines tightly regulate its synthesis. The half-life of IgE is roughly two days.

Structure of an Antibody

• The antibody molecule comprises two identical light chains and two identical heavy chains, which create a flexible Y-shaped structure. Each of the four chains has a variable (V) region contributing to the amino terminus's antigen-binding site and a constant (C) region establishing the isotype.
• The heavy chain's isotype determines the functional characteristics of the antibody. Many noncovalent interactions and disulfide bonds attach the light chains to the heavy chains. The V sections of the heavy and light chains couple in each arm of the Y to create two identical antigen-binding sites located at the tips of the arms of the Y.
• Antibody molecules may cross-link antigens and attach them significantly more firmly when two antigen-binding sites are available. The carboxy-terminal domains of the heavy chains make up the trunk of the Y or Fc fragment.
• The movable hinge regions connect the Y's arms and trunk. Antibodies of various isotypes differ in their Fc fragment and hinge regions, determining their functional characteristics. However, all isotypes share a similar general structure for the domains.

Role Of Antibodies

• Defence from Pathogens: Antibodies are essential for the body's defence against bacteria, viruses, and parasites. They can identify and attach to specific pathogens, stopping them from infecting the body's cells.
• Stimulation of immune response: Antibodies act as messengers that signal the immune system to activate its response. When an antibody binds to a pathogen, it stimulates the immune system to produce more antibodies. Also, it activates other cells, like white blood cells, which help to destroy the pathogen.
• Neutralization of toxins: Some toxins produced by bacteria or other pathogens can be neutralised by antibodies. This helps to prevent damage to the body's cells and tissues.
• Disease diagnosis: Antibiotics can also be employed as a diagnostic tool to ascertain if a person has been exposed to a specific infection. Antibody tests can find antibodies in the blood, which show that a person has been exposed to a particular infection.
• Treatment of Autoimmune disorders: Antibodies can also be utilised to treat autoimmune illnesses, conditions where the immune system erroneously targets healthy body components. Antibodies can inhibit the activity of auto-reactive antibodies, thereby limiting the side effects.
• Prevention of infection: Antibodies can also be used as a prophylactic measure to prevent infection. For example, passive immunisation involves the administration of antibodies to a person to protect against a specific pathogen. This can be done through vaccination or the administration of immune serum.

The Use Of Antibodies In The Fight Against Infectious Diseases

Antibodies play a crucial role in the fight against infectious diseases. The ability of antibodies to recognise and neutralise specific pathogens makes them an essential tool in preventing and treating infections.

One use of antibodies in the fight against infectious diseases is vaccination. Vaccines contain antigens that stimulate the production of antibodies, allowing the immune system to recognise and respond more effectively to future infections. Vaccines can prevent the spread of infectious diseases by providing passive immunity and reducing their severity in those infected.

In addition to vaccination, antibodies can also be used as a form of treatment for infectious diseases. Antibody-based therapies, such as monoclonal antibodies, are designed to mimic the action of natural antibodies in the body. These therapies neutralise the pathogen and prevent it from infecting healthy cells.

Another use of antibodies in the fight against infectious diseases is through convalescent plasma. Convalescent plasma is the blood plasma of recovered individuals and contains high levels of antibodies specific to the pathogen that caused their illness. When administered to individuals with active infections, these antibodies can neutralise the pathogen and reduce the severity of the disease.

Antibodies FAQs

Q1. What purpose is served by an antibody?

Ans. A protein produced by plasma cells, a subset of white blood cells, in response to an antigen, a material that triggers a particular immunological reaction in the body. Only one particular antigen may be recognised by each antibody. This binding serves to assist in the destruction of the antigen.

Q2. What materials make up antibodies?

Ans. Heavy and Light Chains Comprise an Antibody Molecule. Four polypeptide chains comprise the fundamental structural component of an antibody molecule: two identical light (L) chains, which typically contain approximately 220 amino acids each, and two identical heavy (H) chains, which typically include about 440 amino acids each.

Q3. How are antibodies produced?

Ans. When foreign molecules enter the body, the immune system produces host proteins called antibodies. These foreign molecules are known as antigens, and the immune system's molecular identification of them causes the development of antibodies specifically designed to bind each antigen.

Q4. Which body part makes antibodies?

Ans. Spleen. Blood is filtered by the spleen, which also destroys old or damaged red blood cells and bacteria. It also generates immune system defences against disease, such as antibodies and lymphocytes.