Now we should take a look at some of the specific cell labels.
Give a couple examples of these cell labels that
you might see in the extracellular matrix.
Extracellular matrix, just matrix means stuff in general.
So on the outside we will see lots of glycoprotein tags,
for example, when we are thinking about ABO blood typing.
Each of the A and B labels are glycoproteins
that exist on the outside of the red blood cells.
So our body will know that it's our type blood.
If we were to put type B blood into a type A person,
then that type B blood would be recognized as foreign
because the type A person doesn't have that label.
So glycoproteins are labels. Glyco means that it's got
protein component and it also has glucose component.
The other class that we see are glycolipids.
Again the sugar is directly attached to the glycolipids,
those are more involved in communication of the cells.
So finally we can look at major histocompatibility proteins.
These are other labels that there's a lot of
active research going on in it at the moment.
Major histocompatibility proteins
identify "self" from "non-self".
So an example would be the sorts of things we see
with the red blood cell and A and B labelling.
Or in the immune system, we may sometimes see there are
cancer cells or invading cells that are not displaying self labels.
These major histocompatibility proteins
are made by our immune system to identify invaders.
It's a very active area of research currently.
But simply they're cell labels, identifying "self" from "non-self".
We call them MHC proteins.
So some cells interact so closely
because they are part of the same tissue
and they need to actually physically be connected to each other.
So that's where the simplest form of connection
will be seen with these cadherin based junctions.
This is an example of where we have a single transmembrane domain
or two of them, one from each cell
and they connect with each other.
You can see that in the example here,
the lower cell membrane has a single pass protein
and it's attached to an actin molecule.
So one of the cytoskeletal elements.
That way, that protein is held stably in the membrane and
it can associate with a similar protein on its neighbouring cell.
And so these cadherin based junctions,
being anchored to the cytoskeleton
allow cells to connect to each other.
So very simple junctions but many of the other junctions that
we'll explore will be based on the same kind of concept.