General Article Heena CHANGE

What are T cells (T lymphocytes)?

T cells are a type of white blood cell called lymphocytes. They’re also called T lymphocytes. Lymphocytes play an essential role in your immune system. Your immune system fights infection-causing pathogens (viruses, bacteria, fungi and parasites) and harmful cells, like cancer cells.

Your lymphocytes include T cells and B cells. Both types are part of your body’s defense. B cells make proteins called antibodies to fight pathogens. T cells protect you by destroying harmful pathogens and by sending signals that help control your immune system’s response to threats.

What are the different types of T cells?

There are two main types of T cells:

• Cytotoxic T cells: Cytotoxic T cells are also called CD8+ cells because they have a CD8 receptor on their membranes. These cells get their name from “cyto,” which means cell, and “toxic,” which means poisonous or harmful. Cytotoxic T cells kill cells infected with viruses and bacteria, and they also destroy tumor cells.
• Helper T cells: Helper T cells are also called CD4+ cells because they have a CD4 receptor on their membranes. Unlike cytotoxic T cells, helper T cells don’t kill cells directly. Instead, they send signals that tell other cells in your immune system how to coordinate an attack against invaders. Helper T cells signal cytotoxic T cells, B cells and another type of white blood cell called a macrophage.

Although they’re not considered one of the main T cell types, regulatory T cells (suppressor cells) play an essential role in your immune system. These cells reduce the activity of other T cells when necessary. They can prevent T cells from attacking your body’s healthy cells.

Additional Common Questions

What is the difference between T cells and antibodies?

Both T cells and antibodies protect you from pathogens, but they play different roles in your immune system. B cells are the other type of white blood cell (lymphocytes). It’s B cells (not T cells) that make antibodies, a specific type of protein that kills harmful invaders. While B cells send antibodies to kill harmful cells, cytotoxic T cells kill harmful cells directly.