In the fight against coronavirus, a key component of the human immune system has come under the spotlight: antibodies.
These Y-shaped proteins have made top news recently because Covid-19 shoots do not produce as many of them that work against the highly mutated Omicron variant compared to previous strains – at least not without a booster.
Trained by both vaccines and infection, antibodies seize the tip protein, which bounces off the surface of the coronavirus, preventing it from entering cells and making the host ill.
But even though antibodies are rightly celebrated, they are not the only game in town.
In fact, “there is a complex and coordinated response that is truly beautiful from an evolutionary point of view,” explains Harvard immunologist Roger Shapiro.
Here are some key points:
‘Carpet bombers’ of the innate immune system
In the minutes and hours after the virus first rings, signaling proteins send out alarms to recruit the hard but weak animals into the “innate” immune system.
The first to the scene are “neutrophils”, which make up 50 to 70 percent of all white blood cells and are quick to fight but also to perish.
Others include hungry “macrophages” who snatch pathogens down and spit out key points to help train their wiser counterparts, threateningly called “Natural Killer” cells and “dendritic” cells that pass on their intelligence to more elite warriors.
“It’s a bit like carpet bombing of the whole area, and hopefully you harm the attacker as much as possible … while calling into headquarters to get your SEAL units ready to go,” said John Wherry, an immunologist at University of Pennsylvania.
B and T cells: Intelligence officers and trained assassins
If the invaders are not driven away, the “adaptive” immune system comes into play.
A few days inside an initial infection, “B cells” go up to the threat and start pumping out antibodies.
Vaccination also trains B cells – mainly inside the lymph nodes in our armpits, near the injection site – to become primed and clear.
Shapiro compared them to intelligence personnel who had vital information about threats.
The most potent kind of antibodies, known as “neutralizing”, are like chewing gum that sticks to the end of a key and prevents it from unlocking a door.
There are other, lesser-known antibodies that are not as sticky as the neutralizing kind – but which still help to catch the virus, pull it against immune cells or call for help and escalate the overall reaction.
B-cell key partners are “T-cells”, which can be broadly divided into “helpers” and “killers”.
“Killers are like assassins, and they go on to attack the cells that have been infected,” Shapiro said – but these assassins also inflict secondary damage for the greater good.
The Auxiliary T cells “are like generals,” added Shapiro, who gathers troops, encourages B cells to increase their production and directs their deadly counterparts against the enemy.
Stop serious illness
Due to its highly mutated tip protein, the Omicron variant can slide more easily by neutralizing antibodies conferred by previous infection or vaccination.
The bad news is that this makes people more prone to symptomatic infection. But the good news is that T cells are not nearly as easy to fool.
T cells have a “periscope” into infected cells where they can look for the virus’s constituents during its replication cycle, Wherry said.
They are much better at recognizing revealing signs of enemies they have encountered before, even if their clever disguises get them past antibodies.
They kill T cells, perform search-and-destroy missions, puncture holes in infected cells, blow them up, and trigger reactions to bring inflammatory proteins known as “cytokines” into the fight.
Depending on the speed of the reaction, a vaccinated person with a breakthrough infection may have mild, cold-like symptoms or moderate, flu-like symptoms – but the chances of serious illness are drastically reduced.
None of this worsens the case for boosters, which skyrocket the production of all types of antibodies and which also appear to train B and T cells further.
“Omicron is worrying, but the glass is still half full – it will not completely avoid our response,” Wherry said.
(With the exception of the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)