The cells and molecules of the immune system work together to provide a coordinated response against infectious agents and abnormal cells. Here are some of the key cells and molecules of the immune system:
- Leukocytes: Leukocytes, also known as white blood cells, are cells that circulate in the blood and lymphatic system and are essential for immune function. The major types of leukocytes include:
- Granulocytes: Granulocytes include neutrophils, eosinophils, and basophils, and are involved in the innate immune response.
- Monocytes: Monocytes circulate in the blood and can differentiate into macrophages and dendritic cells, which are involved in both innate and adaptive immunity.
- Lymphocytes: Lymphocytes include B cells and T cells, and are involved in the adaptive immune response. B cells produce antibodies, while T cells can differentiate into various subsets that have different functions, such as helper T cells, cytotoxic T cells, and regulatory T cells.
- Antibodies: Antibodies, also known as immunoglobulins, are proteins produced by B cells that can recognize and bind to specific antigens on the surface of pathogens. Antibodies can neutralize pathogens, activate complement, and facilitate phagocytosis by immune cells.
- Antigen-presenting cells (APCs): APCs, such as dendritic cells, macrophages, and B cells, are specialized cells that can capture, process, and present antigens to T cells to initiate an adaptive immune response.
- Cytokines: Cytokines are signaling molecules produced by immune cells that can modulate the immune response. Cytokines can promote inflammation, activate immune cells, and regulate cell growth and differentiation.
- Complement proteins: Complement proteins are a group of soluble proteins that can enhance the immune response by facilitating phagocytosis, promoting inflammation, and directly killing pathogens.
- Major histocompatibility complex (MHC) molecules: MHC molecules are cell surface proteins that can present antigens to T cells to initiate an adaptive immune response. There are two types of MHC molecules: MHC class I molecules, which present antigens to cytotoxic T cells, and MHC class II molecules, which present antigens to helper T cells.
These are just some of the key cells and molecules of the immune system. The immune system is a highly complex and dynamic system that involves many other cell types, molecules, and interactions.