In this video we will be talking about acquired immunity. Acquired immunity includes both humoral immunity, as well as cell-mediated immunity. And based on the textbooks I've read, a lot of these texts just make a huge, complicated mess out of this topic. So I'm going to try to break it down Barney style and try to make it as easy as possible. So I will be bringing up an illustration from our Medical-Surgical Edition 2.0 deck. If you are following along with cards, this illustration is on card number four.
Okay. Let's go through the steps of humoral immunity using this illustration.
So first of all, we have an antigen that will bind to an antibody on a B cell. The B cell will engulf the antigen and present it on the surface of the cell by MHC II proteins.
Then this helper T cell here in green will bind to the complex and release cytokines, which are basically like chemical messengers. This will induce this B cell to rapidly divide into plasma cells, as well as memory cells.
These plasma cells will produce and release antibodies that will work against this specific antigen.
The memory cells will become sensitized. But they will not function until the next exposure to the antigen. At that time, when they are re-exposed, they will mount a large and rapid response to that antigen. So they're like, "Yeah. I'm waiting for you. You come around again and you're going to be in trouble." So they're ready to go next time the body encounters that same antigen.
So then we have these antibodies here, which will bind to the antigen. And with that binding, a reaction takes place. And that triggers neutralization and destruction of those antigens.
Now that we've gone through the steps of humoral immunity, let's talk about cellular immunity.
So when that naive T cell comes in contact with the MHC antigen complex, it becomes activated.
And it releases cytokines or those chemical messengers. And those messengers in turn allow for the proliferation and activation of a number of T cells. This includes other helper or inducer T cells, as well as regulatory T cells and cytotoxic T cells.
Let's go through each of those very briefly.
With helper or inducer T cells, these are CD4+ cells. And we'll definitely be talking more about CD4+ cells when we talk about HIV and AIDS. These cells recognize self versus non-self cells. And in response to non-self cells, these CD4+ cells will release cytokines that are basically a call to arms to other white blood cells to come and destroy this non-self cell.
Then we have regulatory T cells. These prevent hypersensitivity or overreaction of the immune system by releasing cytokines that suppress the immune response.
And then finally, we have cytotoxic T cells, which are CD8+ cells. These cells destroy infected, cancerous, or damaged cells.
Okay, now that you have a better understanding of humoral and cellular immunity, let's talk about the differences between active and passive immunity as well as natural and artificial immunity.
With active immunity, your body is actively producing antibodies. So with active natural immunity, your body produces antibodies in response to exposure to a live pathogen.
If you have active artificial immunity, this is where your body produces antibodies in response to exposure to a vaccine.
Then we have passive immunity. So with passive immunity, your body is not making these antibodies. These antibodies are given to you.
So we have passive natural immunity. This is where mom passes antibodies to her baby through the placenta or through the breast milk. So the baby didn't have to make these antibodies. They were a gift from mom.
Then we have passive artificial immunity. This is where a patient is administered immunoglobulins. So they are given antibodies to help them fight an infection. Because their body didn't create these antibodies, there will be no memory cells available if they are exposed to that infection again in the future. However, the antibodies they get through these immunoglobulins will help them fight the current infection.
So hopefully, that's a helpful explanation to help you differentiate these different types of immunity. In my next video, we will be going over immune system malfunction as well as infection. Thanks so much for watching!
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