hi let's talk about lymphocytes lymphocytes or the cells of the lymphatic system are derivatives of
lymphoid stem cells these lymphoid stem cells go through their various stages of progenitor and
precursor cells into their mature formed elements and they fall into three categories T lymphocytes
B lymphocytes and natural killer cells which often behave like cytotoxic T lymphocytes as we'll see
now there are two types of acquired immunity there's cellular or cell mediated immunity and
then there's humoral or antibody mediated immunity cellular mediated immunity is a function of your
T cells and your natural killer cells whereas your humoral mediated immunity is a function of
your B cells which give rise to plasma cells and these plasma cells shed antibodies and let's see
how that might work so there are three types of T lymphocytes or T cells there are T helper cells
cytotoxic T cells and regulatory T cells or T reg or T suppressor cells now what happens is
an antigen presenting cell such as a dendritic cell or a macrophage is going to phagocytose a
pathogen break it down into its constituent parts and then put pieces of it on surface
membrane receptors so major histocompatibility complex proteins these proteins are then going
to present that antigen to other specialized receptors on helper T cells and you can see that
this is all a function of the three-dimensional shape of the antigen these T helper cells are
then able to share that antigen with cytotoxic T cells and what happens is then the cytotoxic
T cell becomes activated and then it can go out and destroy that particular pathogen based on
its antigen signature and typically how this is done is in terms of a complementary action
and with a complementary action whenever that cytotoxic T cell comes into contact with the
antigen out in the body complement or specialized proteins are brought in to the vicinity and these
proteins are very adept at punching holes through the plasma membrane of bacteria and
any surrounding cell so it basically destroys anything in the vicinity T regulatory cells or
T regs are important cells for helping to prevent autoimmunity or helping to prevent the body's own
T lymphocytes from attacking itself B lymphocytes can also be activated by T helper cells but
they're not all necessarily activated by T helper cells it's a very common pathway for them to
become activated and what happens is the T helper cell shares the antigen that it received from the
antigen presenting cell the B cell has a surface membrane receptor they can interact with that
antigen and then it matures into a plasma cell and plasma cells are the cells which shed antibodies
these antibodies or immunoglobulins can then go out and whenever they find that antibody signature
of a pathogen they're able to then destroy it through various means we've talked a little bit
about acquired immunity and about the cells that modulate acquired immunity thank you for your time