Final answer:
CD4 cells are also known as T helper cells, which are vital for the immune response and are not to be confused with cytotoxic T cells, natural killer cells, macrophages, or neutrophils.
Step-by-step explanation:
CD4 cells are also known as T helper cells. These cells are crucial for the immune system, as they play a pivotal role in directing the immune response. Upon activation by antigen-presenting cells, CD4+ T cells can differentiate into several subtypes including TH1, TH2, TH17, or memory T cells, depending on the cytokines they are exposed to.
TH1 cells, for example, secrete cytokines that enhance the activities of other immune cells including cytotoxic T cells, macrophages, natural killer (NK) cells, and neutrophils. They are important for the immune system's fight against intracellular pathogens like viruses. In contrast, cytotoxic T cells (also known as CD8+ cells), natural killer (NK) cells, macrophages, and neutrophils have distinct functions and are not synonymous with CD4+ T helper cells.