Results have shown that 35% of a 68-population sample of healthy adults who took part in the research study had SARS-CoV-2, the Covid-19 causative agent, reactive T cells in their blood.
What are T-cells?
T cells or T-lymphocytes are one type of white blood cell that is responsible for the body’s immune response. These types of cells induce a form of reaction that lets the immune system think that it has already surpassed a previous infection, so if the actual infection sets in, the body is able to fight with pre-existing antibodies.
Cross-reactivity could be the probable cause of this. It is a phenomenon where a particular antibody binds with a different one and is able to fight a new form of infection. This works well for preventing a severe reaction to a foreign body invader but does not bode well for antibody testing as it could cause false positive results.
A disclaimer states that the cross-reactivity, while it protects the non-infected, does not necessarily suggest the end result of a Covid-19 infection.
There are still many loose ends to the study. There are some studies that suggest children below 18 years old do not experience the extreme health dangers of a Coronavirus infection, and the existing hypothesis is the larger amount of T cells present in a younger body. It is also evident that a lot of severely affected patients already have underlying diseases, which implies fewer T cells left to fight a new oncoming infection.
With the measures taken to manage the virus outbreak, antibodies are the ones given the most attention in terms of vaccines and tests. But the role of T cells should not be left unnoticed.
It apparently didn’t come as a surprise that the human body would develop some form of immunity against Covid-19 since the causative virus is a new hybrid strain of some already existing coronaviruses that humans are commonly exposed to.
"SARS-CoV-2 is the seventh human coronavirus that has been discovered, and four of the human coronaviruses are what we call community-acquired coronaviruses, and together those four are responsible for 25% of our common colds," says Dr. Amesh Adalja of Johns Hopkins University Center for Health Security.
Another study testing blood samples from donors taken in the span of 2015 and 2018, also proved the existence of “preexisting immunity.” Alessandro Sette and Shane Crotty, from the University of California, San Diego say, "it is now established that SARS-CoV-2 pre-existing immune reactivity exists to some degree in the general population. It is hypothesized, but not yet proven.”