Types of immune responses: Innate and adaptive, humoral vs. cell-mediated | NCLEX-RN | Khan Academy

Summary

This video delves into the intricacies of the immune system, focusing on the nonspecific innate immunity and its two lines of defense: physical barriers and inflammatory responses involving phagocytes. It introduces lymphocytes as key players in the specific adaptive immunity, highlighting B lymphocytes and their role in the humoral response against pathogens in bodily fluids. The distinction between humoral and cell-mediated immunity is also briefly touched upon, setting the stage for further exploration in upcoming videos.

Takeaways

• 🛡️ The nonspecific immune system acts as the body's first line of defense, including physical barriers like skin and stomach acid.
• 🔍 The innate immune system includes a second line of defense that is nonspecific, responding to foreign substances without recognizing specific pathogens.
• 💊 Inflammatory responses are part of the nonspecific immune system, helping to direct resources to areas of infection.
• 🌀 Phagocytes, a type of white blood cell, play a crucial role in engulfing and destroying foreign particles.
• 🧬 Nonspecific immune responses are common across many species, suggesting an ancient evolutionary origin.
• 🌟 The specific immune system is thought to be a more recent evolutionary adaptation, providing targeted responses to specific pathogens.
• 🔬 Lymphocytes are a key component of the specific immune system, with B cells and T cells being the main types.
• 🦴 B cells develop in the bone marrow and are part of the humoral response, targeting pathogens in body fluids.
• 🔄 T cells mature in the thymus and are involved in the cell-mediated response, dealing with pathogens that have infiltrated body cells.
• 🏥 Helper T cells play a role in activating the humoral response by interacting with B cells.
• 🛑 The humoral response is the immune system's reaction to pathogens in the body's fluids, while the cell-mediated response deals with pathogens inside cells.

Q & A

What is the primary function of the nonspecific immune system?

The nonspecific immune system serves as the body's first line of defense against pathogens, providing immediate but non-targeted protection. It includes physical barriers like skin and stomach acid, as well as cellular responses like inflammation and phagocytosis by cells like dendritic cells, macrophages, and neutrophils.

What is the difference between the first and second line of defense in the nonspecific immune system?

The first line of defense consists of physical barriers like the skin and mucous membranes that prevent pathogens from entering the body. The second line of defense involves responses that occur after pathogens have breached the first line, such as inflammation and the action of phagocytes to engulf and destroy the invaders.

Why are phagocytes considered nonspecific in their immune response?

Phagocytes are considered nonspecific because they do not recognize and target specific types of pathogens. Instead, they have receptors that can recognize general signs of 'shadiness' or foreignness, such as the presence of double-stranded DNA found in viruses, and then engulf and destroy these pathogens.

How does the presence of double-stranded DNA relate to the nonspecific immune response?

In the nonspecific immune response, phagocytes have receptors that can detect double-stranded DNA, which is typically found in viruses. This allows them to target and engulf viruses without needing to identify the specific type of virus, demonstrating the nonspecific nature of this defense mechanism.

What is the role of the specific immune system in comparison to the nonspecific immune system?

The specific immune system, also known as the adaptive immune system, provides targeted defense against specific pathogens. It involves lymphocytes that can recognize, remember, and mount a more effective response upon subsequent exposures to the same pathogen, unlike the nonspecific immune system which provides immediate but generalized defense.

What are the two main types of lymphocytes and where do they develop?

The two main types of lymphocytes are B lymphocytes (B cells) and T lymphocytes (T cells). B cells develop in the bone marrow, while T cells mature in the thymus. The 'B' in B lymphocytes historically comes from the bursa of Fabricius in birds, but it also stands for bone marrow where they are produced in humans.

What is the humoral response and how does it relate to B lymphocytes?

The humoral response is a part of the specific immune system that involves B lymphocytes and takes place in the body's fluids. It is responsible for combating pathogens that are circulating freely in the body's fluids, such as viruses and bacteria that have not yet infiltrated cells.

How do B lymphocytes contribute to the humoral response?

B lymphocytes contribute to the humoral response by producing antibodies that can specifically recognize and bind to antigens on the surface of pathogens. This binding can neutralize the pathogens, mark them for destruction by other immune cells, or activate the complement system to destroy the pathogen.

What is the cell-mediated response and how does it differ from the humoral response?

The cell-mediated response is a part of the specific immune system that involves T lymphocytes and is primarily focused on combating pathogens that have infiltrated body cells. It differs from the humoral response, which operates in the body's fluids and targets pathogens that are not yet inside cells.

What are the different roles of T lymphocytes in the immune system?

T lymphocytes have various roles in the immune system, including helper T cells that assist in activating B cells and cytotoxic T cells that can kill infected cells. These roles are part of the cell-mediated response, which is distinct from the humoral response that involves B cells.

Outlines

00:00

🛡️ Nonspecific Immune System Defenses

This paragraph discusses the innate or nonspecific immune system, which includes the body's first line of defense such as skin, stomach acid, and skin oils. It explains that these barriers are nonspecific, meaning they do not target specific pathogens but rather act as a general deterrent to any foreign substance. The paragraph also introduces the second line of defense, which includes the inflammatory response and phagocytes such as dendritic cells, macrophages, and neutrophils. These cells are part of the leukocyte family and play a role in engulfing and destroying pathogens without specificity. The speaker emphasizes the nonspecific nature of these defenses, which is a common feature across many species, contrasting it with the specific or adaptive immune system that will be discussed in future videos.

05:02

🧬 B Lymphocytes and Humoral Immune Response

The second paragraph delves into the specific immune system, focusing on B lymphocytes, also known as B cells. These cells are part of the adaptive immune system and are produced in the bone marrow, historically named after the bursa of Fabricius in birds. The speaker plans to discuss T lymphocytes in a future video, but for now, concentrates on B cells' role in the humoral immune response. This response targets pathogens that are circulating in the body's fluids before they have infiltrated cells. The speaker contrasts the humoral response, which deals with extracellular pathogens, with the cell-mediated response, which will be the focus of the next video and involves T cells that target cells that have been infiltrated by pathogens. The paragraph provides a foundational understanding of how the immune system adapts to different types of threats.

Keywords

💡Innate immune system

The innate immune system is the body's first line of defense against pathogens. It is nonspecific, meaning it does not target specific pathogens but rather provides a general defense mechanism. In the video, the innate immune system is discussed as the first response to pathogens, including the body's physical barriers like skin and stomach acid, and cellular responses such as inflammation and phagocytosis by white blood cells.

💡Nonspecific immune response

A nonspecific immune response is a broad reaction to foreign substances without targeting specific pathogens. The video explains that this response includes actions like inflammation and the activity of phagocytes, which engulf and destroy foreign particles without recognizing their specific identity.

💡Phagocytes

Phagocytes are a type of white blood cell that engulfs and digests pathogens, cellular debris, and other foreign substances. In the context of the video, phagocytes such as dendritic cells, macrophages, and neutrophils are part of the nonspecific immune response, playing a crucial role in the body's defense mechanism by consuming and eliminating invaders.

💡Inflammatory response

The inflammatory response is part of the body's immune system and involves a series of protective steps to eliminate harmful stimuli and initiate tissue repair. The video mentions that this response is a part of the second line of defense in the nonspecific immune system, helping to recruit immune cells to the site of infection or injury.

💡Leukocytes

Leukocytes, also known as white blood cells, are a crucial component of the immune system. They are involved in defending the body against both infectious disease and foreign materials. The video clarifies that all phagocytes discussed are types of leukocytes, highlighting their role in the nonspecific immune response.

💡Specific immune system

The specific immune system, also known as the adaptive immune system, is a highly specialized subsystem of the immune system that provides a focused defense against specific pathogens. The video introduces this system as a more targeted and evolved response compared to the innate immune system, involving exposure and memory of past encounters with pathogens.

💡Lymphocytes

Lymphocytes are a type of white blood cell that plays a central role in the specific immune response. They are divided into B lymphocytes and T lymphocytes, each with different functions. The video emphasizes that lymphocytes are a key part of the adaptive immune system, with B cells being the focus of the video's discussion.

💡B lymphocytes (B cells)

B lymphocytes, or B cells, are a type of lymphocyte that matures in the bone marrow. They are part of the humoral immune response and are responsible for producing antibodies to neutralize pathogens. The video discusses B cells as a significant component of the specific immune system, highlighting their role in the humoral response.

💡Humoral response

The humoral response is a part of the specific immune system that involves the production of antibodies by B cells to neutralize pathogens in the body's fluids. The video explains that this response is particularly effective against pathogens that are circulating in the bloodstream or lymphatic system before they have a chance to invade cells.

💡Cell-mediated response

The cell-mediated response is a part of the specific immune system that involves T cells and is primarily responsible for targeting and destroying infected cells. The video mentions that this response is crucial when pathogens have already infiltrated cells, and it will be discussed in more detail in a future video.

Highlights

Introduction to the nonspecific or innate immune system.

Explanation of first line barriers such as skin and stomach acid.

Description of the second line of defense in the nonspecific immune system.

Discussion on the nonspecific immune system's response to unidentified threats.

Mention of inflammatory response and phagocytes in the immune system.

Clarification that all discussed phagocytes are types of white blood cells or leukocytes.

Differentiation between nonspecific and specific immune responses.

Evolutionary perspective on the specific immune system as a newer adaptation.

Introduction to the adaptive immune system and its reliance on exposure to pathogens.

Role of antigen-presenting molecules in the specific immune system.

Definition and importance of lymphocytes in the immune response.

Distinction between B lymphocytes (B cells) and T lymphocytes.

Historical background of the naming of B lymphocytes.

Explanation of where T lymphocytes mature and the origin of their name.

Focus on B lymphocytes and their role in the humoral response.

Definition and importance of the humoral response in the immune system.

Comparison between the humoral response and the cell-mediated response.

Discussion on the immune system's approach to dealing with cells infected by viruses or bacteria.

Transcripts

In the last video, we talked a little bit

about the immune system.

In that video, we focused on the nonspecific or the innate

immune system.

So let me write that.

And even in the nonspecific immune system, we subdivided

that into kind of the first line barriers.

And those were things like the skin, or the stomach acid, or

the acidity of the oils on the outside of your skin.

These are just natural barriers to not allowing

things inside of your body, but then once they get in-- so

you can almost imagine these were the

first line of defense.

And then you had your second line of defense, but these are

still nonspecific-- and when we say nonspecific, it means

that they don't necessarily know what type of virus, what

type of protein, what type of bacteria.

They just know that this thing looks shady.

Let me eat it up.

Let me kill it.

Let me have an inflammatory response.

So in there, we said, well, there's an inflammatory

response, which I'm actually going to talk about after we

do videos on the specific immune system.

You have your inflammatory response, which really just

gets things to where the action is at and then you also

have your phagocytes, which are these cells that are

engulfing things.

And just so you know, all the phagocytes that we talked

about in the last video, these are all instances of white

blood cells or leukocytes.

These phagocytes right here, these are all-- I talk about

dendritic cells and macrophages and neutrophils.

These were all white blood cells.

These weren't all the kinds of white blood cells.

We're about to talk about more-- and the other word for

white blood cell is also leukocyte.

So that is nonspecific.

Well, one, it just doesn't let you in, but then when you're

in, it says, hey, you're just shady.

I'm going to eat you up.

I have receptors.

You have some double stranded DNA floating around.

Only viruses have double strand DNA.

I'm going to eat you up.

I don't know what type of virus you are.

I don't know if I've seen you before or not.

That's why it's nonspecific.

Now the really interesting thing about our immune

system-- and this nonspecific, this exists across many, many,

many species and types of organisms. But the specific is

kind of a-- it's thought to be a newer adaptation.

What I'm going to talk about is the specific immune system

that's particular to humans.

That's our other classification.

Let me do it like that.

So then you have your specific-- or you can imagine

it's an adaptive immune system.

You've probably heard of things like that.

I have resistance to that bacteria or that virus.

So this is adaptive.

And it's really all based on having exposure to things.

And within the specific immune system, we talked a little--

when we talked about the antigen presenting molecules

that phagocytes do-- that plays a role in this.

We're going to go into more detail, but I don't want to

confuse you.

But the main actors here are called lymphocytes, not to be

confused with leukocytes-- because they still are

leukocytes.

So let me write this down.

These are specific.

Phagocytes, for the most part, are nonspecific, but both of

these are white blood cells.

Lymphocytes are another type of white

blood cell or leukocyte.

Don't want to confuse you with this convoluted diagram, but I

just want to make the terminology clear.

When someone talks about a white blood cell, they're

really just talking about a set of cells that when people

first tried to separate the components of blood-- you'd

have your red blood cells that would kind of settle in the

bottom, then you'd have this layer of white frothy stuff in

the middle that was really made of white blood cells, and

then on the top, you had the fluid, the plasma from your

blood, kind of the watery part.

So that's where the name came from, but they have different

roles, but they interact with each other.

Now lymphocytes can be divided into B lymphocytes, usually

referred to as B cells-- and T lymphocytes.

And the B and T just come from where they're developed.

B lymphocytes were first recognized in

the bursa of Fabricius.

That's why it's called B.

That's actually a part of birds that participate in the

immune system.

And so the B came from bursa, but B also applies to the

human immune system because it's produced in bone marrow.

So that might be an easier way to remember.

It's produced in bone marrow.

It's developed in bone marrow, but historically, the B came

from the bursa of Fabricius, just in case you want to know.

But it's easy to remember.

The B could also stand for bone marrow because that's

where it's produced.

T lymphocytes actually do start off in the bone marrow,

but they mature and become what they are in the thymus.

So that's where the T comes from.

Now in this video, I'm going to focus just on the B

lymphocytes-- because frankly, if I focused on everything, it

would be an hour-long video.

But the B lymphocytes frankly on some level-- well, I don't

want to pick and choose favorites, but something in my

brain-- I just really like the B lymphocytes.

So the B lymphocytes participate in what's called

the humoral response.

And I'll tell you what humoral means in a second.

You'll see that T lymphocytes participate in what's called

the cell mediated response and we're going to do that in a

future video.

They actually do certain classes of T lymphocytes.

We'll see that there are helper T cells and there are

cytotoxic T cells.

I know it's all very confusing the first time you see it, but

that's why I just want to focus on just

this part right here.

We're going to see in the future that the helper T cells

play a role in amplifying and really activating

this humoral response.

But a simple way to think about the difference between

the humoral response and the cell mediated response is,

when I get infected-- let's say I get

infected by a virus, right?

At first, when a virus comes into my system, it's just

floating around in the fluids in my system.

The fluids of our system-- that's really what humoral

responds to, into the humoral fluids of your body.

So you have your viruses.

These are little viruses floating around.

So while they're floating around and they're not sitting

inside of cells, that's where the humoral response

can come into play.

Same thing if we have little bacteria floating around and

they haven't infiltrated cells yet.

They're just floating around in the fluid, then the humoral

response can be useful for that.

Now if all of a sudden, these guys have infiltrated cells--

so if the cells are now infected with the virus and

they're producing the viruses using the mechanisms of the

cell to produce more, then all of a sudden we have to be a

little bit more sophisticated in how we deal with these

cells and how we deal with the viruses because they're not

just going to be floating around anymore.

We probably want to just kill this cell even though it was

one of our own, but now it's helping to make viruses.

Or maybe it's been colonized by bacteria.

So in either case, you want to kill this.

And we'll talk more about that in the cell mediating.