CD4 T cells, also known as helper T cells, are a type of white blood cell that play a crucial role in the immune system. They help coordinate the body's response to infections by signaling other immune cells, such as B cells and CD8 T cells, to take action against pathogens. CD4 T cells recognize specific antigens presented by antigen-presenting cells and are essential for developing a strong immune response. These cells are characterized by the presence of the CD4 protein on their surface. A healthy population of CD4 T cells is vital for maintaining immune function, and their levels are often measured in individuals with HIV/AIDS to assess immune health. Low levels of CD4 T cells can lead to increased susceptibility to infections and diseases.