CD4 cells, also known as CD4 T cells, are a type of white blood cell that plays 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 macrophages, to attack pathogens. CD4 cells are essential for maintaining a healthy immune response. These cells are particularly important in the context of HIV/AIDS, as the virus specifically targets and destroys CD4 cells, leading to a weakened immune system. Monitoring CD4 cell counts is vital for assessing the health of individuals living with HIV and determining the effectiveness of treatment.