Cells of the immune system have profound immunoregulatory influences on each other. This regulation is mediated in large part by potent bioactive molecules, called cytokines, which may have autocrine, paracrine, or systemic effects. These polypeptides and glycoproteins are produced by diverse types of cells and act on many different types of cells by binding to high affinity receptors on their surfaces. Their functions include 1) activating or attracting specific types of leukocytes, 2) regulating cell division, 3) modulating the production or actions of other cytokines, 4) promoting or abrogating inflammation, 5) directing certain cells to switch the types of proteins that they produce, and 6) influencing the production of cellular or humoral immunity. Those produced principally by lymphocytes have been termed lymphokines and those principally produced by monocytes and macrophages, monokines. Interleukin is also used to designate many of these agents.
A detailed description of the sources, target cells, and principal functions of these agents is beyond the scope of this presentation, but a synopsis of that information is found in Table 1-2 and the specific roles of certain cytokines are discussed in sections of this chapter that will follow.
Ligands, such as surface molecules, on certain cells of the immune system that bind to receptors on other types of cells may activate the cells bearing the receptors and thus modulate immune responses. Interactions between T cell receptors and the processed peptide in the context of the MHC molecule are examples of the importance of such ligand (peptide)-receptor (T cell receptor) interactions in the immune system.
A detailed description of the sources, target cells, and principal functions of these agents is beyond the scope of this presentation, but a synopsis of that information is found in Table 1-2 and the specific roles of certain cytokines are discussed in sections of this chapter that will follow.
Ligands, such as surface molecules, on certain cells of the immune system that bind to receptors on other types of cells may activate the cells bearing the receptors and thus modulate immune responses. Interactions between T cell receptors and the processed peptide in the context of the MHC molecule are examples of the importance of such ligand (peptide)-receptor (T cell receptor) interactions in the immune system.
