This unit is going to deal with immunology.
Immunology is an up and coming science that
deals basically with antibodies and antigens
and how we can recognize them.
An antigen is any chemical that is recognized
as non-self and that triggers an immune response
in a mammalian system.
An antibody is a “Y” shaped proteins that
are created by an organism and that bind to
antigens.
These have a typical Y shape.
Its got 3 edges to it.
Two these edges are called antigen binding
sites, which is where the antigen will bind
to.
These have lock and key specificity, meaning
they will only bind on to one type of antigen.
And therefore, you have many different kinds
of these in your system.
They are all produce by B-cells.
And, when we deal with them, now a days we
deal with monoclonals, and we will get into
that in a minute.
When we deal with antibodies, we call these
serological tests,
because we normally used blood serum that
has antibodies or antigens in it.
We have direct tests which test for the presence
of antigens.
In a test like this we might be looking at
something like do you have the organism that
causes strep throat?
Or is Salmonella present in a specific food
supply.
And we are testing for the presence of antigens.
In indirect tests, that test for the presence
of antibodies.
Many times they ask you if you have had chickenpox,
and how strong is your reaction to it.
Because if you don’t have a strong enough
reaction you’re going to need to be revaccinated.
You would do an indirect test to test for
the presence of antibodies in your blood stream,
to find out how many antibodies you have.
We have qualitative tests.
Qualitative test says it tests for the presence
or absence.
This is like a pregnancy test.
It is a yes / no.
Either you are or you are not.
We also have quantitative tests.
Test for the amount.
Again we go back to the chicken pox example.
When you get tested you look for how much
do you have.
Now we start out over here with a four-legged
furry creature.
The amount of antibodies that you needed determined
the size of the four-legged furry creature.
In the past they used some rather large ones.
This got to be expensive because you had to
have the organism in a sterile environment.
Nowadays the procedure has changed.
What they do is they take the four-legged
furry creature, they inject it with antigen,
its immune system reacts to that, and then
they are able to do a splenectomy, and remove
the cells that produce the antibodies.
These then get fused with myeloma cells that
are grown in a cell culture, and what we get
is we get something called a hybridoma.
The hybridoma has the longevity of the myeloma
cells and is also able to secrete antibodies.
These are then plated out so that we can determine
exactly which one is producing the antibodies
that we want.
We can take that particular material, and
we can grow that particular material in a
cell culture.
And now, all day long, we have a constant
supply of new antibodies being created by
these perpetual cells.
So we get quality control and much higher
levels of production.
Another test method that we have is what we
call a diffusion test.
Now we start out with an agarose material
that is a very thin type agarose.
It is 0.1 to 0.2 %, which is much thinner
than what you find in culture media.
So it is kind of like a solidified water.
We place the material we are trying to test
in these little wells, that we have perforated
in the agar.
And what will happen is the material will
diffuse out.
When it comes in contact with a compatible
material, you will get a line of precipitation
forming, indicating the presence of the antigen
and antibody for that particular test.
When you look at this, you can see the two
lines of precipitation in here as we are able
to complete this test.
Another test we have is called the ELISA test
or the Enzyme-Linked ImmunoSorbent Assay.
The test is rather simple.
We start out with a microtiter plate.
We place into it our antibodies that are for
the specific antigen that we are looking for.
These hook on to the bottom of the plate.
We then rinse out any material that has not
attached in.
We add our sample.
If the sample has the antigen present in it,
the antigen will bind onto the antibodies.
Again we rinse.
Then we add another antibody, that is just
like the first one, but, in this case, it
has an enzyme liked onto the antibody.
If the antigen is present, these will bind
on to the antigen.
If the antigen is not present, these will
not bind on.
The amount of antigen present actually determines
how many of these get bound.
We then take that plate and we add a substrate
that will react with the enzyme and that will
cause the substrate to break apart into the
products.
The product will give us a color development.
The intensity of the color will depend on
how much enzyme we have present in this.
When we look at this particular plate, you
can see that this has various colors.
And this shows the development of colors at
different concentrations of antigen, so that
we can see color development.
Again, this is qualitative, because the darker
the color, and you can actually measure these
colors, the darker the color, the more antigen
is present.
This is a dip stick type test.
We can use this for a lot of different materials.
In this particular case it is plant material.
Our sample is placed on the inside.
The sample is macerated.
And that is going to release the content of
the cells.
You take your dip stick and insert it in.
The material is pulled up on the inside.
And what you get is a result like this.
The upper one has a single band.
Therefore, the answer is no.
The bottom one has a double band.
Therefore, the answer is yes.
This is the type of test that we have for
things like Strep pyogenes in the throat,
as well as, this particular one which is looking
for a pathogen in a plant sample.
A pregnancy test works in the same manner.
This is an agglutination test.
And in an agglutination test, what you are
trying to find is whether or not the material
is present.
And what it does is it forms large particles.
The large particles come together and they
clump and they fall out of solution.
This particular one is a blood test and we
do blood testing in order to determine different
antigens that are present on cells.
So when we look at immunological testing,
there are a lot of different possibilities
that we have.
And they are all made possible by antibodies
that are produced in mammalian systems that
we can use to test for specific antigens.
