Immune cells, also known as immune system cells, are an important component of an organism’s immune system. They play a crucial role in the defense against diseases and infections. There are different types of immune cells, each of which performs specialized functions. The best known are the lymphocytes, which are divided into two main categories: T lymphocytes and B lymphocytes. T lymphocytes recognize and destroy infected cells, while B lymphocytes produce antibodies to fight pathogens. Another important type of immune cell is the phagocyte, which includes macrophages and neutrophil granulocytes. These cells specialize in the ingestion and digestion of pathogens such as bacteria and viruses. They recognize and destroy these pathogens by phagocytosis. In addition, there are other types of immune cells such as natural killer cells, which can attack and destroy infected cells and cancer cells, and dendritic cells, which play a key role in activating other immune cells. The immune system is a highly complex network of closely communicating immune cells. Together, these cells work to protect the body from pathogens and maintain balance in the body. In the event of an infection, immune cells first recognize the pathogen through specific receptors on their surface. They then activate an immune response in which they either attack the pathogen directly or produce specific proteins (antibodies) to kill the pathogen or render it harmless. The interaction of the various immune cells is crucial for an effective immune response. If the immune system is weakened or does not function properly, this can lead to various diseases and infections. Conversely, an overactive immune system can lead to allergies, autoimmune diseases or inflammation. Research into immune cells and their interaction has led to important advances in medicine, such as the development of vaccines and immunotherapies. This research allows us to better understand the immune system and develop more targeted treatments for various diseases. In summary, immune cells are crucial for the functioning of the immune system and the protection of the body against diseases and infections. Research into these cells has increased our understanding of the immune system and opens up new possibilities for the development of therapies to treat various diseases.