Introduction to Immunity - Online Tutor, Practice Problems & Exam Prep

Immunity is the body's ability to eliminate disease-causing microbes, categorized into innate (nonspecific) and adaptive (specific) immunity. Innate immunity provides routine protection from a broad range of pathogens at birth, utilizing physical barriers like skin and chemical defenses. Adaptive immunity evolves over time, targeting specific pathogens through antibodies and specialized cells like B and T lymphocytes. Antigens, foreign substances that induce immune responses, interact with antibodies, triggering various immune reactions to eliminate pathogens effectively.

Innate vs. Adaptive Immunity

In this video, we're going to begin our introduction to immunity. And so when our bodies are attacked by foreign microbes, we have various defense mechanisms to help protect us from those attacking microbes. And so we collectively refer to these defense mechanisms as our immunity. And so immunity can be defined as our ability to eliminate disease-causing microbes from our bodies and to help protect our bodies against environmental agents such as pollen, for example. Now, susceptibility, on the other hand, refers to the lack of immunity towards some kind of agent. Now our immune systems are really broken up into 2 major groups, and so really there are 2 general types of immunity. The first is going to be innate immunity, and the second is going to be adaptive immunity. Now, innate immunity is also sometimes referred to as nonspecific immunity. And so innate implies that this is going to provide routine protection that is present at birth, and that's really what this innate term refers to. That fact that we are born with these innate protective immune responses. Now, the reason that it is also referred to as non-specific immunity is because this type of immunity protects us against a very broad range of many different types of pathogens. Now, the second major group of our immune system is going to be adaptive immunity. And adaptive immunity is also sometimes referred to as specific immunity. And so the adaptive part of adaptive immunity implies that it includes components that are capable of adapting or changing over time, and that means that as we expose ourselves to new environments and different types of environmental agents, our adaptive immune responses are capable of changing and adapting and evolving to become better at protecting us over time. And, it is also referred to as specific immunity because this type of immunity will provide us with protection against very specific types of pathogens.

As we move forward in our course, we're going to talk a lot more details about both innate or nonspecific immunity first, and then we'll talk a lot more details about adaptive or specific immunity much later. However, it is important to know that although generally innate and adaptive immunity are taught separately, that some parts of innate immunity will complement some parts of adaptive immunity and vice versa. And so there is a little bit of crosstalk between innate immune responses and adaptive immune responses. And as we move forward in our course, that's important to keep in mind, and it is also going to be something that we'll try to make connections between the two as we move forward in our course.

If we take a look at our image down below, notice that the left-hand side over here is focused specifically on innate immunity, which once again recall is also referred to as nonspecific immunity that provides routine protection that is present at birth against the broad range of many different types of pathogens. And innate immunity includes things such as physical barriers, such as our skin and mucus membranes. It also includes chemical defenses such as antimicrobials, acids, bases, and things of that nature, and we'll get to talk a lot more about these chemical defenses as we move forward in our course. And it also includes a collection of several different innate immune cells, which once again we'll get to talk a lot more details about them as we move forward in our course.

Now over here, the right side of the image is focused specifically on adaptive immunity. And once again, adaptive immunity is also referred to as specific immunity, and it includes components that adapt or change over time in response to changing environments and also exposure to different types of pathogens. And adaptive or specific immunity provides protection against very specific types of pathogens. And adaptive immunity includes antibodies, which are these Y-shaped proteins that are capable of binding to foreign molecules and generating some kind of immune response, and we'll get to talk a lot more about antibodies as we move forward in our course. And adaptive immunity also includes adaptive immune cells, such as for example, B cells and T cells. And again, we'll get to talk about adaptive immune cells as we move forward in our course as well. But for now, this here concludes our brief introduction to immunity and how our immune systems are broken up into 2 major categories, innate immunity and adaptive immunity. And again, there is sometimes going to be some parts of each type of immunity that are going to complement each other, and they work together in some cases. And so, we will get to learn a lot more as we move forward, so I'll see you all in our next video.

Antigens & Antibodies

This video, we're going to briefly discuss antigens and antibodies. And so antigens and antibodies, but specifically antibodies, play a significant role in adaptive immunity or specific immunity. Now the term antigen really is a broad term that refers to any toxin or foreign substance, such as a foreign microbe, that induces an antibody immune response. And so antibodies are going to be Y-shaped proteins that recognize and bind to specific antigens. And so if we take a look at our image over here on the left-hand side, notice that we're showing you this Y-shaped protein right here. And this Y-shaped protein is indeed going to be our antibody. And notice that the antibody has these 2 antigen-binding sites here that are in green, allowing the antibody to bind to an antigen. And notice here in red, we have our antigen. Now antigens and antibodies are capable of triggering an immune response, and the immune response can be different. And we'll get to talk about many of the different types of immune responses that antibodies are capable of generating as we move forward in our course, later in our course in a different video. But for now, just so that you can get an understanding, notice that in this image, we're showing you a pathogen, which is down below, some kind of disease-causing agent, a microbe, for example. And this microbe on its surface has these specific antigens on its surface. And, our bodies are capable of when the antibody binds to the antigen, it's able to trigger some kind of immune response. For example, it can allow a host immune cell, such as this one right here, to target the pathogen and eliminate the pathogen. And so notice that we're showing you the immune cell is attacking the pathogen through the release of specific chemicals here, and that will kill the pathogen and eliminate the pathogen. And so you can see here how antibodies can play a very important role in immunity, and we'll get to talk a lot more about antibodies later in our course when we talk a lot more about adaptive immunity. But for now, this here concludes our brief introduction to antigens and antibodies, and we'll be able to talk a lot more about immunity as we move forward in our course. So I'll see you all in our next video.

Here’s what students ask on this topic:

What is the difference between innate and adaptive immunity?

Innate immunity, also known as nonspecific immunity, provides routine protection from a broad range of pathogens and is present at birth. It includes physical barriers like skin and mucous membranes, as well as chemical defenses such as antimicrobials and acids. Adaptive immunity, or specific immunity, evolves over time and targets specific pathogens. It involves specialized cells like B and T lymphocytes and the production of antibodies. While innate immunity offers immediate defense, adaptive immunity provides a more tailored response and improves with exposure to different pathogens.

How do antibodies function in the immune system?

Antibodies are Y-shaped proteins that play a crucial role in adaptive immunity. They recognize and bind to specific antigens, which are foreign substances like toxins or microbes. Once bound, antibodies can neutralize the pathogen directly or mark it for destruction by other immune cells. For example, an antibody can bind to a pathogen's surface antigen, triggering an immune response that allows host immune cells to target and eliminate the pathogen. This process is essential for the body's ability to adapt and respond to specific threats over time.

What are antigens and how do they trigger an immune response?

Antigens are foreign substances, such as toxins or microbes, that induce an immune response. When an antigen enters the body, it is recognized by antibodies, which are Y-shaped proteins. The binding of an antibody to an antigen triggers various immune responses, such as the activation of immune cells that can target and eliminate the pathogen. This interaction is a key component of adaptive immunity, allowing the body to specifically target and remember pathogens for more effective responses in the future.

What are the main components of innate immunity?

Innate immunity includes several key components that provide immediate, nonspecific defense against pathogens. These components include physical barriers like the skin and mucous membranes, which prevent pathogen entry. Chemical defenses such as antimicrobial peptides, acids, and enzymes also play a role in neutralizing pathogens. Additionally, innate immunity involves various immune cells, such as macrophages, neutrophils, and natural killer cells, which can quickly respond to and eliminate invading microbes. These components work together to provide a broad, first line of defense against infections.

How do B cells and T cells contribute to adaptive immunity?

B cells and T cells are essential components of adaptive immunity. B cells are responsible for producing antibodies that specifically target antigens. When a B cell encounters its specific antigen, it can differentiate into plasma cells that secrete large amounts of antibodies. T cells, on the other hand, have various roles. Helper T cells activate other immune cells, including B cells and cytotoxic T cells, which directly kill infected cells. Both B and T cells have memory cells that provide long-lasting immunity by remembering past infections and responding more rapidly upon re-exposure.