Antibody Responses

Antibody Responses

Subject – Science and Tech

Context – New study on antibody responses

Concept –

• A recent study looked at the neutralising antibody responses generated by breakthrough infections in individuals vaccinated against SARS-CoV2.
• The researchers learnt that the degree of antibody response depended on whether a person has had one, two, three, or four exposures to the spike protein through infection, vaccination, or a mixture of the two.
• Among their study subjects, those who had completed a three-vaccination protocol, and those who had been vaccinated after recovering from COVID-19, and those with a breakthrough infection after having been vaccinated launched almost comparable neutralising antibody responses.

Antibodies

They are proteins made by the immune system to fight antigens, such as bacteria, viruses, and toxins. The body makes different immunoglobulin to combat different antigens.

The five subclasses of antibodies are:

• Immunoglobulin A (IgA), which is found in high concentrations in the mucous membranes, particularly those lining the respiratory passages and gastrointestinal tract, as well as in saliva and tears.
• Immunoglobulin G (IgG), are involved in the secondary immune response (IgM is the main antibody involved in primary response). IgG can bind pathogens, like for example viruses, bacteria, and fungi, and thereby protects the body against infection and toxins. Comprising up to 80% of the antibodies found in the human body, IgG is the smallest, yet most abundant human antibody, and that of other mammals. IgG can be found in all bodily fluids, and is the only antibody that can protect a foetus by passing through the mother’s placenta.
• Immunoglobulin M (IgM),is the largest antibody, and it is the first antibody to appear in the response to initial exposure to an antigen. B-cells create IgM antibodies as a first line of defense. Their large size gives them excellent binding avidity, and can pick up trace amounts of infection to mark for recognition by phagocytes. IgM is primarily found in serum and due to its size, it cannot diffuse well, and is found in the interstitium only in very low quantities.
• Immunoglobulin E (IgE), which is associated mainly with allergic reactions (when the immune system overreacts to environmental antigens such as pollen or pet dander). It is found in the lungs, skin, and mucous membranes.
• Immunoglobulin D (IgD), which exists in small amounts in the blood, is the least understood antibody.