You've heard the word "immunity" more in the last three years than in the previous 30 years, haven't you?

The degree to which the body reacts to the virus, in addition to the amount of viral load that is inhaled, has a big impact on each person's own body's ability to fight the virus, which is often referred to as immunity.

The word "immunity" derives from the Latin word "immunitas," which means the body's ability to fight disease. The immune system can protect the body against foreign viruses, bacteria, fungi, parasites, allergens and other invasions to fight back, protect the body organs and maintain the normal operation of the body.

As a mother with a biological background, I am most concerned about how to improve the immunity of my children. Then I have to work from the ground up.

The first thing we need to know is, how does the virus get into our bodies? What exactly builds our body's immunity against viruses?

First, the process of virus invasion, that is a invisible "cell war"

If viruses were an invading enemy, every cell in our bodies would be equal to about a city. This is a cell war without smoke.

⭕️ First came the outer fortifications -- our skin barrier.

It mainly includes skin, mucous membranes and secretions. Before the virus enters the cell, it will first pass through the skin mucous membranes and other places. We sneeze to clear the respiratory tract of viruses; The viruses we eat in our stomachs are also killed by digestive enzymes, stomach acids, and so on.

But viruses don't stop there, and there are always viruses that get past the outer defenses.

⭕️ It's time for the teams of immunoglobulins and white blood cells that patrol the cells.

Before the virus actually reaches the cell membrane, patrolling immunoglobulins (antibodies) can spot an invading enemy and bind to special proteins on the virus's coat, denying it the chance to enter. In addition to neutralizing pathogens, immunoglobulins "lock" viruses together so that patrolling white blood cells can spot them more quickly and devour them.

But if there are too many invading viruses and not enough antibodies, some will elude the patrols and reach the cell membrane.

⭕️ Cell membranes, like the walls of a city, are not so easy to enter.

The virus has to have a key to bind to receptors on the cell membrane and trick the cell into thinking it is harmless. For example, the receptor of coronavirus is human angiotensin converting enzyme 2(ACE2)[1], and the expression level of this receptor is high in type II alveolar epithelial cells, esophageal epithelial cells, ileum and colon, so the upper respiratory tract and lungs are often the first to be attacked.

If there are enough antibodies, they bind to the virus's "keys," depriving them of the ability to bind to receptors on the cell surface. But if there aren't enough antibodies, some of them manage to bind to a receptor on the surface of the cell membrane, where the cell mistakes it for something useful and opens its gates.

⭕️ At this time, the cell city inside the close street fighting is about to start - the enemy (virus) has entered the cell!

The virus's ultimate goal is to reach the nucleus, the city's command center, and replicate.

But it's not that easy -- the virus gets wrapped up in the endosome, which secretes acid that breaks down proteins on the outside of the virus. If the virus is being held tightly by the immunoglobulin, it may be eliminated.

But if few antibodies bind to the virus, the virus releases a special protein that dissolves the membrane of the endosome and then makes its way to the nucleus with the help of the dynamin, using the cell's internal "highway" microtubule system.

⭕️ And the cell isn't sitting still.

A special protein looks for anything around the microtubule that marks the antibody and binds to it. The more they bind, the easier it is for the lysosome to find them and get rid of them.

If the virus hadn't been labeled by the antibody up front, it would have escaped the lysosome here. It reaches the nucleus. This is where the virus's protein coat breaks off and genetic material enters the nucleus through the nuclear pore, opening up massive replication.

At this point, there's nothing the invaded cell can do.

At this point, the cell "city" officially declared the city slope.

It usually takes about two hours for the virus to reach the surface of the skin and penetrate a cell city.

Of course the real picture is more complicated

⭕️ But that's not all -- the dying cell sends out special signals via fragments carrying viral antigens to the outside of the cell to warn surrounding cells that an invasion has occurred. If the fragment is recognized by patrolling white blood cells, they will destroy the dead cell city. One of the other things that white blood cells do is they call out to people, to various types of immune cells to come and kill the enemy.

⭕️ The massive copies of the virus begin to attack surrounding cells and take over the city. But our immune systems have also been activated.

The immune cells begin their counterattack -- the B-lymphocytes differentiate into plasma cells and produce large amounts of antibodies, and various phagocytes, such as macrophages, arrive on the battlefield and start eating the infected cells. Helper T cells (Th cells) stimulate B cells to produce more antibodies, attracting more T cells or phagocytes to come and devour pathogens and damaged cells. Killer T cells directly attack infected cells and fight the virus.

At this point, we may not even be aware that such a vicious cell war has taken place in the mucous membrane of the skin. Usually, the immune system succeeds in preventing the virus from spreading widely.

The immune cells are fighting back

⭕️ But it's also possible that the immune system can't fight the virus for a while. That's when the immune system lets the fever help!

Phagocytes release a lot of inflammatory factors and cellular thermogenic factors during combat, and tell the brain's thermoregulatory center through the blood circulation system: we have an enemy invasion here, quickly raise your temperature!

When the body temperature rises, viral activity and replication are temporarily suppressed, allowing immune cells to reach the battlefield more efficiently. Large amounts of antibodies are produced, and phagocytes rapidly engulf the virus and infected cells. In order to prevent the spread of the virus, the immune system goes "crazy" and will be willing to kill the wrong, and the surrounding normal cells will be attacked. Not only do we have a fever, but we also feel aches and pains all over.

This round of intense battle may be over in one go, or it may require repeated battles, so the fever often repeats.

But fortunately, most of the time, the immune system wins.

Then the body will cough, spit and other ways to expel the virus, dead cells, our bodies slowly return to normal.

The B and T lymphocytes also add the virus to the database, and the next time they encounter the same enemy, they can fight back more quickly.

Of course, the real process of pathogen infection and the immune system's response is much more complex, involving a large number of intracellular and intercellular signaling mechanisms, and the collaboration of various immune cells. Different pathogens, viruses, bacteria, fungi, etc., cause different infections.

Second, what role does immunoglobulin play in it?

Immunoglobulin is basically what we hear about antibodies. In the process of virus invasion and counterattack, it plays an important role in neutralizing the virus and laying "death mark" for the virus.

There are five common antibodies in our body [2], which are IgA, IgD, IgE, IgG and IgM, of which the front "Ig" represents Immunoglobulin.

They look something like this: the individual molecules are roughly Y shaped, and the two Y-shaped branches are areas that recognize and bind antigens (special proteins on the surface of the virus).

The picture is from my immunology courseware

Different antibodies play different roles:

Immunoglobulins are at almost every stage of the battle between cells and viruses.

As the frontline forces of the immune system, they are patrol teams outside the city that first spot an invading virus and quickly bind to it, partly to tag the virus so that immune cells can recognise the intruder more quickly; It also disables the virus's "key" by binding to a spike protein on the virus's surface, preventing it from getting inside the cell membrane.

Immunoglobulins are sentinels in the cell's street battles, marking viruses that lysosomes recognize, capture, and kill before they can enter the nucleus.

When the "war" enters the territory phase, the virus begins to replicate in large numbers in the body, the constantly working B lymphocytes also produce large quantities of antibodies. With the combination of antibodies, the virus can be neutralized and lose the ability to bind cells. With the combination of antibodies, the virus is easier to be recognized and phagocytic by various immune cells.

In summary, antibodies play three main roles in each link of immunity war:

It binds to a virus (pathogen) and loses its ability to infect cells

Labeling pathogens stimulates immune cells, such as macrophages, to recognize and eliminate them

Stimulating other immune processes, such as the complement pathway (which you can think of as a chain of enzyme reactions), causes the pathogen to rupture and die. While the antibody cannot kill the virus directly, it can, through specific binding, give the pathogen a "death notice."

If there are enough antibodies in the body, the virus can be identified and cleared away early in the infection, and you won't even notice that a virus-cell battle has just taken place in the mucous membrane of your nose.

But if there aren't enough specific antibodies at the beginning, and the virus gets inside the cell nucleus and starts replicating, and the battle lines are drawn, the immune system has to wage a much larger war against the virus. We may feel nasal congestion, body pain, fever and other uncomfortable symptoms, and even appear repeated high fever, serious inflammatory reactions.

In general, the more antibodies you have, the easier it is to keep the disease at a milder stage in the war against the virus.

3. Where does immunoglobulin come from?

Immunoglobulins are so important. How are they produced?

Our body acquires immunity, including innate immunity and acquired immunity.

Innate immunity is something that we are born with, and it's kind of like our defenses outside the city -- our skin, mucous membranes, cilia, and so on, and some non-specific immune cells. Even babies are born with innate immunity.

Acquired immunity, as its name suggests, is learned and acquired. Every time our bodies encounter a pathogen or have an immune response stimulated by a vaccine, our bodies produce antibodies against that antigen. Some antibodies can persist in the body for a long time, such as hepatitis B surface antibodies, which can last eight to 10 years. Some antibodies slowly decrease in titer over time, such as flu vaccines, which are usually readministered annually.

In addition to producing antibodies, immune cells build up a "database" of the pathogen. In their fight against pathogens, activated B cells produce a type of "memory B cell" that can survive in the body for a long time. The next time you encounter the same pathogen, the memory B cells activate quickly, allowing the immune system to respond faster and earlier and clear the pathogen out of the body.

If you accumulate antibodies during actual combat when you get sick, vaccination is equivalent to producing antibodies during actual combat exercises.

But we have the impression that the newborn baby has not encountered any pathogens, so theoretically there is no antibody ah, why in the first few months are rarely sick?

This is the magic of the human body, although the newborn is not exposed to any pathogens, but will get the corresponding antibodies from the mother's body through the placenta, which is a kind of passive immunity. In addition to getting it from the placenta, breast milk, especially colostrum, also gives the baby a lot of active antibodies. Studies have shown that SIgA content in colostrum produced by mothers on the first, second and third days after delivery is up to more than 10mg/ml, more than 10 times that of mature milk [3][4].

Babies receive valuable IgG and IgA antibodies from their mothers through breast feeding. These antibodies form the baby's initial immunity.

Not only that, previous studies believed that antibodies mainly recognize and neutralize pathogens in the extracellular environment, and the intracellular infection can only rely on T lymphocytes. However, a recent study from nature in 2022 showed that specially modified antibodies produced by mothers during pregnancy can protect infants from intracellular pathogens through vertical transmission or breast milk [5].

Four, How else can we get more immunoglobulin? Is oral supplementary immunoglobulin an IQ tax?

The production of antibodies is either acquired passively through initial breast milk or, over time, through repeated infection with pathogens and various active vaccinations.

And different people, the difference in immunity is often antibody type and titer difference.

Timely and scheduled vaccination is the best way for us to get antibodies.

I still remember when I was a child, there was a little boy of my age in my village. When everyone was vaccinated against meningitis as arranged by the school, the family of that little boy did not let him get vaccinated for whatever reason. Did not expect that the next year he was infected with encephalopathy, due to treatment is not timely, resulting in permanent mental deficiency.

After my own baby was born, I arranged for him the full set of national immunization vaccines, including the self-paid vaccines, and timely vaccination was almost as important as the physical examination two years before his birth and every three months to six months.

Besides getting vaccinated, how can we get more antibodies to boost our immunity?

I have to mention that there's been a lot of discussion about injecting protein.

But! This method is not useful or necessary for people with normal immunity. Second, it is intravenous injection, daily use of it to improve immunity is unrealistic! This is equivalent to taking antibodies from someone else's plasma. There is no single component of the antibodies, and they are injected directly into the patient's blood, only working in certain circumstances. It's metabolized after two weeks.

Therefore, do not grab it, it can not help you improve your daily immunity, but its production cycle is very long, blind buying will let patients who really need to buy this life-saving medicine.

So, is oral immunoglobulin feasible? Does it help with immunity?

This brings us to another substance that's been discussed a lot -- bovine colostrum (BC).

Like human colostrum, bovine colostrum contains a lot of immunity and biogenesis