If this antigen entered the body, the body
would generate humoral immune response (antibodies)
or cell mediated immune response (cellular
response).
The antigen must have large molecular weight,
foreign to the body and preferably complex.
Sometimes, pay attention to this
a foreign organism enters your body without
a large molecular weight nor complexity, so
it cannot stimulate immune response, because
it has low molecular weight.
This body can bind to a protein in my body
resulting in a large molecular weight = antigen.
This generates an immune response.
It has gained molecular weight, became complex
and it is originally foreign.
This immune response will be against the foreign
substance and the body protein it is attached
to, such protein is called a carrier.
This carrier holds the foreign substance.
This foreign substance is called Hapten.
So, again, what does hapten mean?
It is an incomplete antigen (no large molecular
weight, no complexity, only foreign).
It cannot stimulate immune response when introduced to the body as it
is not antigen, it is a hapten, but it can bind to a protein
carrier in your body and become an antigen.
The body will then form an antibody against
it and against its own protein.
Understood?
What is the importance of hapten?
This hapten could be a drug.
When you take any medicine for acidity, blood
glucose or blood pressure, if this drug stimulated
an immune response, then it won't work.
So, it is not an antigen.
But this drug is considered hapten, it can
bind to a protein in your body.
For example, if penicillin was treated as
a hapten, it will bind to albumin forming
an antigen.
This will stimulate an immune response leading
to allergy.
So we are done with the hapten.
Imagine that we have a rat here.
A low molecular weight substance was injected
to it (hapten), it won't move.
But if a protein was added to the hapten,
the hapten would gain a large molecular weight,
an immune response
will be stimulated against the foreign substance.
The point is some drugs can enter our bodies
as haptens but never act.
They can attach to red blood cells, they increase
in size (RBCs are carriers now), so the body
releases antibodies against this drug and
RBCs.
The RBCs will be destroyed, and you will be
infected by Hemolytic anemia.
The red blood cells will be destroyed.
Since the RBCs were destroyed after the drug
attachment, we call it autoimmune.
It means that the body generates an immune
response against itself, its own RBCs, because
the hapten was attached to it, so the body
treated them as an antigen.
The RBCs structure has changed so the body
released antibodies against it.
The RBCs are destroyed, anemia occurs (Hemolytic
anemia).
When the body attacks its own protein, we
call it an autoimmune disease.
What are the antigen types?
