Lymphocytes: Definition, Functions & Types

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  • 0:00 Lymphocytes
  • 0:35 Types Of Lymphocytes
  • 1:35 Functions Of Lymphocytes
  • 3:30 Lesson Summary
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Lesson Transcript
Instructor: Derrick Arrington

Derrick has taught biology and chemistry at both the high school and college level. He has a master's degree in science education.

Our bodies contain numerous types of cells. In this lesson, you will learn about a type of cell known as a lymphocyte. You will also gain an understanding of the types of lymphocytes, as well as their functions in the body.


At some point in our lives, we all deal with sickness in one form or another. The manner in which we're able to deal with sickness normally depends on the strength of our immune system. One of the main tools in the arsenal of our immune system is a group of specialized cells known as lymphocytes.

Lymphocytes are a type of white blood cell that function as part of the immune system. Their various functions allow them to properly respond to foreign invaders in the body. Some lymphocytes work alone, while others are able to coordinate with other cells.

Types of Lymphocytes

There are three types of lymphocytes, known as T cells, B cells, and natural killer cells. T cells get their name because they are developed in the thymus gland. These cells are distinguished from other lymphocytes by the specialized T-cell receptor molecule that is located on the surface of the cell. This molecule is important in immunity because it recognizes antigens and is able to bind to them.

B cells are an important part of the immune system. B cells get their name because they mature in the bone marrow of humans, and in the bursa organ of birds. These cells are distinguished from other lymphocytes by a protein on their surface known as the B-cell receptor. This protein is specialized to recognize and attach to specific antigens.

Natural killer cells are lymphocytes that are known to be cytotoxic. This means that they have the ability to kill other cells. These cells are an important part of the immune system because they are able to recognize virally infected cells, as well as some types of tumor cells, and kill them before they cause a great amount of harm.

Functions of Lymphocytes

All lymphocytes function as a part of our immune defense. As we go about our daily activities, we come into contact with all types of foreign molecules that have the potential to make us sick. The immune system is crucial for recognizing foreign material in our bodies and either killing the material or removing it in some form. An antigen is a substance that evokes a response from our immune system. When antigens are found by lymphocytes, an immune response is triggered to defend our bodies.

Lymphocytes, such as T cells and B cells, have their specific binding sites that allow them to recognize and attach to antigens that have entered the body. T cells perform several vital functions in the immune system, including assisting other white blood cells during immune responses and maintaining immunological balance in the body.

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