T cells do not release antibodies. Some of them have surface receptors that recognize a specific antigen, but the antigen must be presented by another cell. The antigen-presenting cell is usually a phagocytic white blood cell called a macrophage. The T cell divides and differentiates into several types of cells: Helper T cells also known as T_H, T₄ or CD4 cells due to the presence of the CD4 glycoprotein on the cell surface; cytotoxic (T_C) and suppressor (T₃) cells or CD8 cells due to the CD8 glycoprotein and memory T cells.