Hello. I'm Luis Graca.
I'm a Professor of Immunology at the University of Lisbon Medical School,
and I direct a research group at Instituto de Medicina Molecular, also in Lisbon.
We live surrounded by viruses and other microorganisms.
One of the challenges that we face is how to protect ourselves
against organisms that can adapt very quickly.
The life-cycle of a virus or a bacterium is very short compared with our own life-cycle,
and as a consequence,
with a body that cannot change very fast,
we need to adapt to new infections that may
happen next year or in a few years with agents
that have a chance to evolve to overcome an immune response
that was effective to clear that same pathogen today.
We know from experience,
that if we get flu this year,
we will be protected from another flu infection in the same season,
but we cannot be protected against a flu infection from next year,
because the flu virus from next year,
will be different from this year's viruses.
One way the immune system developed to tackle this problem,
is to have receptors that can anticipate
any molecular change that can happen in a virus in
order to be ready to respond to an infection,
no matter what are the mutations that were acquired by that virus.
Many years ago it was discovered by Karl Landsteiner,
the same scientist that discovered the blood groups,
that in fact there are antibodies that can recognize many different antigens.
When he immunized animals with different antigens,
he found that no matter what was the antigen used for the immunization,
it was always possible to get an immune response against that antigen.
Even when antigens were not normally present in nature,
the immune system had the ability to create
antibodies specific to that particular antigen.
This means that the immune system is complete,
and can anticipate any mutation that the flu virus from next year may acquire.