If you’re wondering, what has
immunology ever done for me?
Well the answer’s quite simple -vaccination; a really easy
procedure that protects all of us from infectious disease.
Vaccination is providing protection by utilizing
either pre-existing components of the immune
response or more commonly, by inducing the
generation of antigen-specific memory cells.
We can divide immunization into
active or passive immunization.
The most common form is active immunization
where there is injection of antigen.
This often requires additional
components, for example an adjuvant.
The immune response
is generated in vivo.
It takes time to develop but it provides
long term protection because there is
generation of memory T-cells and memory
B-cells in response to the vaccination.
There is the potential to develop both
a cell-mediated and a humoral response.
In contrast, passive immunization is
the injection of pre-formed antibodies.
This provides immediate protection,
but the protection is short term.
Antibody has a half life of about
three weeks in the circulation.
So the protection provided by these injected
antibodies doesn’t last for a very long time.
It only provides humoral immunity.
The pathogen needs to be susceptible
to antibody mediated destruction.
If cytotoxic T-cells are required, then
passive immunization will not be helpful.
And there is the risk of
adventitious pathogen transfer.
Let’s have a look at some
examples of passive immunization.
Horse antisera against snake venom,
botulism toxin and diphtheria toxin
can be administered to individuals
exposed to these toxic agents.
Pooled human immunoglobulin against Hepatitis A or B,
measles, rabies, tetanus, varicella zoster, and humanized
monoclonal antibody against respiratory syncytial virus can
all be given to patients that are exposed to these agents.
With regard to active immunization,
vaccines can induce neutralizing antibodies.
Viruses need to bind to cell surface
receptors on cells in order to infect cells.
Antibodies can block the binding of
viruses to their cell surface receptors.
Bacteria can produce toxins,
these can poison our cells.
Antibodies can block the toxic
activity of bacterial toxins.
Finally, in order to establish an infection, many
microorganisms need to colonize surfaces in the body.
Antibodies, particularly dimeric
secretory IgA can prevent colonization.
Let’s have a look at the immunological
basis of active vaccination.
Here we have a diagram showing you the magnitude of the immune
response following the first encounter
with antigens from a pathogen.
This will be a natural infection
that we would be exposed to.
The primary immune response is
fairly weak and short lived.
However, if instead of encountering the natural
infection, that is potentially pathogenic, we give
a modified version of the pathogen; in other words
the antigens are seen in a non-pathogenic form.
Then we elicit this
primary immune response.
And importantly, memory T-cells
and B-cells are generated.
Looking at the secondary immune response, if the subsequent
encounter is with the actual
pathogen itself, the individual goes
straight into making a secondary immune response because the
primary immune response was elicited by the non-pathogenic form.
And now there is a secondary immune
response which is strong and long lasting.
And this occurs in response to the
actual pathogen upon the first encounter.
So because memory cells are already
present as a result of the vaccination,
a secondary immune response occurs on
the first encounter with the pathogen.
This is here really just
for your information.
I’m not going to read through this.
You can read through
it at your leisure.
But it provides you with the current
vaccination schedule for the USA.