Antigens & Antibodies- The Immune System

The year 2020 was really one for the history books. It was an unprecedented year for human health due to the spread of the COVID-19 virus. As science progresses each day, we are making huge advancements in discovery and understanding. However, that’s not always well translated to the general public. We are bombarded with words like zoonotic, antigen, SARS-CoV-2 and antibodies in our daily media, but what are they and what do they mean for us?COVID-19 a brief history

Coronavirus is zoonotic disease; this means that the disease has been transmitted from an animal source to a human. The original animal species to transmit the disease is unknown. The genetic sequence of the virus has ecological origin in bat populations. However, because contact between bats and humans is minimal, it’s likely that the virus had transmitted to another animal before infecting humans.  It’s believed that the first human case of COVID-19 was reported in Wuhan City, China in December 2019. The full genetic sequence for SARS-CoV-2 was shared with the world on the 11th-12th January.

The first cases of novel coronavirus in the UK were confirmed on 31st January 2020 in two members of the same family. By the end of March, we had 19,784 confirmed cases within the UK. On the 7th February 2020 Public Health England (PHE) released a laboratory tested diagnostic test. Following this, the UK government announced a nationwide lockdown on 23rd March. Since, we have seen a series of local and national lockdowns to manage the spread of the disease. Remarkably, in less than a year the UK had created, released and begun rolling out the initial vaccination programme. In a landmark piece of scientific history, on the 8th December 2020, the first COVID vaccine was administered to 90-year-old Margaret Keenan.  

Symptoms of COVID-19

Although you are likely very aware of common symptoms of COVID here is a quick synopsis:

  • A high temperature
  • A dry and continuous cough
  • Loss or change in taste and smell

You do not have to have all these symptoms to have coronavirus, some people carry just 1, or none at all, this is called asymptomatic. How does the immune system work?

The immune system is a complex network of organs and cells working together to defend your body from invading pathogens. Pathogens can include viruses, microorganisms and bacteria. The main body of cells that govern the immune system are the white blood cells. The immune system branches into the innate and adaptive immune system.

The innate system is made up of our first line of defence and non-specific cells. The first line of defence includes our skin, eyelashes, sweat, gastric acid and mucous. Whereas, the nonspecific cells includes macrophages, phagocytes, neutrophils, basophils, eosinophils and mast cells. This branch of the immune response is activated between 0-96hours of infection.

Following this 96 hour window, the secondary branch of the immune system kicks in, this is called the adaptive or specific immune response. This is made up of T and B cells. B cells produce y-shaped proteins called antibodies which are specific to the antigens found on the surface of the invading pathogen. These antibodies get released from B-cells and lock onto the antigens of the invading cell. In this case, the virus. Consider the antibodies the key, and the antigens the lock. Whereas, there are a few types of T-cells, cytotoxic, helper and killer T-cells. The helper cells stimulate the B-cells to produce antibodies in order to tag the invading pathogen. Also, it stimulates killer cell production. These cells, as the name suggests, kill/destroys the invading pathogen by recognising foreign antigen. Whereas cytotoxic T cells destroy the tagged infected cells by trapping them in granule sacs with digestive enzymes. This slowly destroys the infected cells before they spread. Lastly, you have memory cells, these are essential for adaptive immune response. These are how our immune system learns to quickly recognise and act against invading pathogens upon secondary infection. These are often made of Helper and Cytotoxic T cells that convert to memory cells.Antigen and Antibody what’s the difference?

Yes, the names are very similar and can get very confusing but let’s break them down for our understanding. Which came first the chicken or the egg? In this case, which came first the antigen or the antibody, the answer is the antigen.

 

 

Image Source: https://www.cancer.ca/en/cancer-information/cancer-101/what-is-cancer/the-immune-system/?region=on

Antigens

Antigens are presented on the cell surface of the invading pathogen. They are mainly made up of protein but can be made from lipids, carbohydrates and nucleic acids too. They stimulate the human immune response.

Antibody

Antibodies are also known as Immunoglobulins. Antibodies are stimulated by the presence of the antigen of the invading cell. These antibodies are produced by the human’s own B-cells. Antibodies are made of protein, there are 5 basic types of Immunoglobulins (Ig) IgM, IgG, IgE, IgD and IgA. Each binding site (paratope) is specific to the binding site of the antigen (epitope). The role of the antibody is to render the pathogen immobile and unable to infect further. Or, the antibody may signal a complement reaction using over 30 proteins to burst or scavenge and ingest the pathogen.

The COVID testing kit.

In more recent times, we have used our understanding of antibodies and antigens to create COVID testing kits which is believed to help us manage the movement of the disease much better. The SARS-Cov-2 virus carries specific antigens on its cellular surface. When infected the body produces specific antibodies to this strain of the virus. Hence, antibody and antigen diagnostic tests.

Antibody Test

The antibody test reveals if a person has previously been exposed to the virus. They are not used to diagnose current infection. This test is done by testing the person’s blood or serum. This may be helpful within the UK right now to identify those who may be vulnerable to infection and might be prioritised for vaccination.

Our Antibody Test:

Our test will deliver a result to you within 15 minutes. Each test has an accuracy value of 97.8% (IgM) and 99.6% (IgG). Each pack will contain the following:

  • 1 x Wipe
  • 1 x Lancet
  • 1 x Pipette
  • 1 x Cassette
  • 1 x Solution
  • 1 x Test kit wallet

The IgM-IgG Combined Antibody Test for COVID-19 is a lateral flow immunoassay used to detect IgG and IgM antibodies of the novel coronavirus in human serum, plasma or whole blood. A lateral flow test is similar to a pregnancy test.

The test strip contains two detection lines (G and M lines) and one quality control line (C). The M-line is fixed with monoclonal anti-human IgM antibody for detecting the novel coronavirus IgM antibody. Wheras the G-line contains a monoclonal anti-human IgG antibody for detecting the novel coronavirus IgG antibody. The quality control antibody is fixed on the C line, the control line confirms the test has worked, this line should show once the test is complete.

A total of three detection lines are possible, with the control (C) line appearing when the sample has flowed through the cassette.

  • Negative Result for novel coronavirus: If only the quality control line (C) appears, and the detection lines G and M are not visible.
  • Positive Result, M only: If both the quality control line (C) and the detection line M appears, then the novel coronavirus IgM antibody has been detected and the result is positive for the IgM antibody.
  • Positive Result G only: If both the quality control line (C) and the detection line G appears, then the novel coronavirus IgG antibody has been detected and the result is positive for the IgG antibody.
  • Positive Result, G and M: If the quality control line (C) and both detection lines G and M appear, then the novel coronavirus IgG and IgM antibodies have been detected and the result is positive for both the IgG and IgM antibodies

Antigen Test

The antigen test reveals if a person has a current infection of the COVID-19 virus. Once the infection has gone, the antigen too will disappear. Be mindful that a negative test result may occur if the test is taken too early.

Our Antigen Test:

Our test will deliver a result to you within 15 minutes. Each test has an accuracy value of 98%. Each pack will contain the following:

  • 1 Test cassette
  • 1 Sterile swab
  • 1 Sample extraction tube
  • 1 Dropper tip
  • 1 Package insert

To start, the swab is inserted into the nostril and mouth to take samples from the nasal cavity or tonsils. The collected sample is then placed into an extraction tube that contains approximately 0.5ml of the preservation solution. After 2 minutes, place the specimen on a testing cassette and the result will reveal within 15 minutes. The accuracy ratings for the antigen test kit are up to 98% accurate and it can be used by medical professionals to confirm current infection.

Glossary

  • Zoonotic- a disease that can be transmitted from animals to people or, more specifically, a disease that normally exists in animals but that can infect humans.
  • SARS-CoV-2- SARS stands for Severe Acute Respiratory Syndrome. COVID-19 was renamed as SARS-CoV-2.
  • Vaccine- A vaccine is a substance that helps protect against certain diseases. Vaccines contain a dead or weakened version of a microbe. It helps your immune system recognize and destroy the living microbe during a future infection.
  • Asymptomatic - Asymptomatic means there are no symptoms. You are considered asymptomatic if you: Have recovered from an illness or condition and no longer have symptoms. Have an illness or condition but do not have symptoms of it.
  • Pathogens- any small organism, such as a virus or a bacterium that can cause disease
  • Antigen- Antigen, substance that is capable of stimulating an immune response, specifically activating lymphocytes, which are the body’s infection-fighting white blood cells.
  • Antibody- Antibody, also called immunoglobulin, a protective protein produced by the immune system in response to the presence of a foreign substance, called an antigen.
  • Innate Immune Response- Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen's appearance in the body.
  • Adaptive Immune Response- Adaptive immunity refers to antigen-specific immune response.
  • Immunoglobulins- Immunoglobulin: A protein produced by plasma cells and lymphocytes and characteristic of these types of cells. Immunoglobulins play an essential role in the body's immune system.
  • Complement- Complement, in immunology, a complex system of more than 30 proteins that act in concert to help eliminate infectious microorganisms.

Panodyne COVID-19 Antibody Rapid Test Kit

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Panodyne COVID-19 Antigen Rapid Test Kit

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