T-helper cells, also known as CD4+ 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 cytotoxic T cells, to take action against pathogens. These cells are activated when they recognize specific antigens presented by antigen-presenting cells. Once activated, T-helper cells release cytokines, which are signaling molecules that enhance the immune response, helping the body to effectively fight off infections and diseases.