Introduction to the Immune System: Study with Video Lessons, Practice Problems & Examples

Immunity is the body's ability to eliminate disease-causing microbes, divided into innate (nonspecific) and adaptive (specific) immunity. Innate immunity provides routine protection from various 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 cells. Antigens, foreign substances that trigger immune responses, interact with antibodies, which are Y-shaped proteins that bind to these antigens, facilitating pathogen elimination. Understanding these mechanisms is crucial for comprehending how the immune system functions.

Introduction to Immunity

In this video, we're going to begin our introduction to immunity. And so when our bodies are attacked by foreign microbes, we actually 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 the fact that we are born with these innate protective immune responses. Now, the reason that it is also referred to as nonspecific 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. Now 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 cross-talk 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 will try to make connections between the 2 as we move forward in our course. And so 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 a lot more about the 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.

Factors that work generically against any foreign substance entering the host are described as:

• A. Innate immunity.
• B. Specific immunity.
• C. Irregular immunity.
• D. Immune metabolism.

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 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, triggering 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 cells and T cells, and antibodies that bind to antigens to facilitate pathogen elimination. While innate immunity offers immediate defense, adaptive immunity provides a more tailored response that 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 trigger various immune responses, such as marking the pathogen for destruction by immune cells. For example, an antibody can bind to an antigen on a pathogen's surface, signaling immune cells to attack and eliminate the pathogen. This process helps the body to effectively target and neutralize specific threats, enhancing the overall immune response.

What are the main components of innate immunity?

Innate immunity consists of several key components that provide immediate defense against a wide range of pathogens. These 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 invaders. Additionally, innate immunity involves various immune cells like macrophages, neutrophils, and natural killer cells, which can quickly respond to and eliminate pathogens. These components work together to offer a broad, nonspecific defense that is present from birth.

What role do B cells and T cells play in adaptive immunity?

B cells and T cells are essential components of adaptive immunity. B cells are responsible for producing antibodies that bind to specific antigens, marking pathogens for destruction. They can also differentiate into memory B cells, which provide long-term immunity by remembering past infections. T cells, on the other hand, come in two main types: helper T cells and cytotoxic T cells. Helper T cells assist in activating B cells and other immune cells, while cytotoxic T cells directly attack and destroy infected cells. Together, B cells and T cells provide a targeted and adaptable immune response.

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

Antigens are foreign substances, such as toxins or microbes, that can induce an immune response. When an antigen enters the body, it is recognized by antibodies, which are Y-shaped proteins that bind specifically to the antigen. This binding can trigger various immune responses, such as marking the pathogen for destruction by immune cells. For example, an antibody-antigen complex can signal macrophages to engulf and destroy the pathogen. This process helps the immune system to effectively target and eliminate specific threats, ensuring a precise and efficient defense.