Stamp the cells and track in real time what the memory cells do after vaccination?

The magic of vaccines is that they effectively create long-lived immune cells, often for decades
.
These immune cells create a protective barrier that prevents or reduces reinfection, as well as a memory that allows us to recognize old invaders like viruses and kill
them before it causes disease.
The antibodies in our blood that act as a barrier are produced by "long-lived plasma cells," and while the importance of these cells has long been known, how and when they are produced after vaccination remains a mystery
.

Until now, a research team led by Dr Marcus Robinson and Professor David Tarlinton from Monash University's Immune Memory Laboratory, published an article in the prestigious journal Science Immunology, showing in real time how immune memory cells are stored in the bone marrow at a rate of about one cell per hour in
the weeks following immunization.
The researchers used the mice's genetic system to map the gradual accumulation
of these cells.
This system, called timestamping, allows researchers to indelibly label all plasma cells for a specific period of time after vaccination and then return later to identify those that survived and therefore lived longer
.
By performing this test regularly after vaccination, the researchers revealed the history of accumulation of these long-lived cells, pinpointing exactly when and where
they were born.

After receiving the vaccination, we still have a great deal of immunity to the disease because our body continues to supply antibodies against this immune disease – basically making sure that the antibodies in our body remain adequate
.
While we already know where these long-lived plasma cells are produced in the body, including the lymph nodes, tonsils and intestines, it's not known
exactly what makes some vaccines keep these cells for decades and disappear after a few months.
Given the global interest in the long-term immunity provided by COVID vaccines, understanding this process becomes even more urgent
.
A mouse model
using fluorescent proteins (called TdTomato proteins) expressed only in cells that produce antibodies to a specific vaccine was used.
Because these cells fluoresce, it is possible to track where individual cells are produced and stored
.

The study used a range of tools to identify those plasma cells
produced by vaccines.
All the plasma cells in the mouse model expressed a fluorescent protein called the TdTomato protein, in which they identified the cells that recognized the vaccine, and finally, by timestamping, they knew when the cells were produced and thus their age
.

Studying the process by which these individual cells are born, matured, and stored to protect us from repeated invasions by specific viruses or bacteria "can help us understand how long-lived plasma cells recruit.
"
”

The complexity of this study allowed the researchers to identify other aspects of specific immune establishment:

• How these plasma cells enter the bone marrow

• When these plasma cells are stored in areas such as bone marrow, do they necessarily replace other cells?

• Or the cells "found" a niche vacated by the previous plasma cell death or migration elsewhere

Mapping of the cells shows that after a mouse was vaccinated with a specific vaccine, about 40,000 persistently present plasma cells
were produced in the bone marrow.
After the initial flourishing, these cells decay at a rate of about 0.
1% per day and have a half-life of about 700 days, which provides both an estimate of the duration of protection and an identification
for further study of the long-lived cells themselves.

Professor Tarlinton said understanding how these long-lived plasma cells are produced, survived and died "will help us regulate their recruitment through different vaccine combinations or delivery strategies, ultimately allowing us to extend the lifespan
of immunity.
" In fact, the journal Nature recently reported on an exciting work describing how changing the vaccination mechanism can significantly affect the characteristics of the immune response, and we will predict the production of these specialized cells, which has been the focus of
our work.
”

Long-lived plasma cells accumulate in the bone marrow at a constant rate from early in an immune response.