Since SARS-CoV-2/COVID was declared a pandemic many have been reviewing basic immunology or biology…
Trying to make sense of the recommendations put in place:

• ✓ Washing your hands…
• ✓ Coughing in your elbow…
• ✓ Mask or no mask…
• ✓ Social distancing…
• ✓ Quarantine…

You may also have gone into your mathematics and tried to understand the science of epidemics, exponential growth, and the infection rate…

All to flatten the curve.

I am convinced that we will get through this pandemic by working together.

To do so, we need to understand WHY we are collectively making the efforts asked by our respective authorities…

The different governments have attempted at educating the population and our work force but you can’t explain something you don’t understand. They as we are, are learning as we go.

Given that the authorities were quite reactive and unprepared the resources were low and the need for education, high.  At first most measures were to protect our health care system, to flatten the curve and make sure that all would get access to decent care if needed.

It is not to protect our own families, really. The measures put in place are to protect our societies as a whole. The confinement measures act similarly to a vaccine, while we develop one. The measures are put into place to protect our vulnerable population and ensure our health care system capacity is not maxed out.

To appreciate the measures taken by some governments at the expense of their economy and to understand the time these measures need to buy…

Let’s take a step back and review some immunology!

Basic immunology or human biochemistry for that matter start with the understanding of ligands and receptors.

LIGANDS AND RECEPTORS

Receptors and ligands come in many forms and play a role in various functions but have one thing in common, they are specific to one another.

Together, they form the basis of the signaling or messaging that occurs in our entire body.

They are matched pairs, with a receptor recognizing specific ligands and a ligand binding to just a few target receptors. Their binding has been compare to the lock and the key.  One lock goes usually with one key but sometimes a master key is also capable of opening multiple doors! Tricky combos.

Receptors are made of proteins. Ligands have more diverse forms… depending on the signaling they convey and the distance they travel to convey that signal. Hormones for instance act as ligands in endocrine signaling and travel large distances in the bloodstream to signal the receptor.

Most are endogenous (internal) signaling molecules, meaning that they are made by our human organisms. Some exogenous (external) molecules, like medication or drugs, “fit” in key receptors and can block or stimulate a signal.

Allergens and antigens are external proteins that act like ligands as they signal some cells to take some action.

THEN THERE IS the immune system.

Our first line of defense to invader pathogens that may cause disease is our skin and our gut. But should invaders pass that first line of defense then we have the adaptive and innate immune system.

The innate system kicks in first and deals with small trouble in a matter of minutes. For instance, when you break your skin to prevent infections, the innate system will send macrophages to destroy rapidly a few invaders.

The innate system with its receptors is great at recognizing common pathogens that have common patterns. As an example, Bacteria can be recognized by a component of their cell wall, common to all bacterial cells.

The innate system, however, is not great at dealing with viruses. To deal with sophisticated pathogens, such as clever viruses, our adaptive immune system is called in.

In the recent weeks, we have picked up much discussion around white blood cells, plasma serum, antigens and antibodies, B and T cells, clones. Perhaps even about major histocompatibility complex (MHC) and memory T and B cells.  They all compose the adaptive immune system.

It is called adaptive as it adapts to what it is exposed. Once it has built a response and developed an immunity to an invader the adaptive immune system will remember that invader.  Overtime, it builds a “database” of the invaders it has been exposed to and can quickly respond to second attempts at invasion.

The adaptive immune system also uses receptors that specific to antigens. Once a new antigen is presented to the immune system…It signals the invader through the bloodstream. The first response to a new antigen may take days to fully build. The response the body builds is the ability to produce massive amounts of antibodies. These antibodies connect as receptors to the antigen-part of a virus (the ligand) and “tags” those copies of the virus for destruction.

Antibodies are very specific to an antigen. Once it has been exposed to an antigen and developed an immunity, the adaptive immune system is able to produce the specific antibodies that will flag the antigens very rapidly for destruction.

It can do that with many different types of antigens but needs days to build a sufficient response when it is first exposed to a new antigen. That is what vaccines do. They expose the adaptive immune system to a safer version of a new antigen so it can build an immunity to it.

Stay tuned for our next post around vaccines development!

Best

IMMUNOLOGY: the science of the immune system. The main function of the immune system is to protect us from infection by potential invader pathogens like viruses.  Should it not be functioning properly, allergy and other immunology conditions can be triggered.
RECEPTORS:  molecules made of proteins associated with our cell metabolism. Located at the cell surface or inside the cell.
LIGANDS: can also be made of proteins but can take many other forms and they travel throughout the body. Examples are:  calcium ions, nitric oxide gas, small peptides, and steroid hormones.  Depending on their form they will signal at the cell surface if they can’t pass through the cell or inside the cell if they can.
ANTIGEN: a toxin or other foreign substance which triggers an immune response in the body, particularly the production of antibodies. A type of ligand.
ANTIBODY: Antibodies are made of proteins that are produced in reaction to a specific antigen (eg. virus). They mark the invaders and signal the immune system for destruction. Antibodies are a type of IMMUNOGLOBULINS. When we talk of antibody we mean immunoglobulin type G (IgG).
VIRUS:  type of microbe that depends on living cells such as animal, plant or bacteria cells, in order to multiply. Although called a microorganism it is not considered a living organisms as it doesn’t have the internal machinery to reproduce.
A VIRUS is a very small ineffective microorganisms that is made of nucleic or ribonucleic acid and a protein coat, sometimes also protected by an envelope (that envelop is made amongst other things of proteins) with a protein section recognized as foreign (the antigen).