3D medical animation still showing secretion of<unk> s<unk> s are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling.<unk> s are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm.<unk> s have been shown to be involved in autocrine, paracrine and endocrine signaling as immunomodulating agents. Their definite distinction from hormones is still part of ongoing research.<unk> s include chemokines, interferons, interleukins, lymphokines, and tumour necrosis factors, but generally not hormones or growth factors (despite some overlap in the terminology).<unk> s are produced by a broad range of cells, including immune cells like macrophages, B lymphocytes, T lymphocytes and mast cells, as well as endothelial cells, fibroblasts, and various stromal cells; a given<unk>  may be produced by more than one type of cell. They act through cell surface receptors and are especially important in the immune system;<unk> s modulate the balance between humoral and cell-based immune responses, and they regulate the maturation, growth, and responsiveness of particular cell populations. Some<unk> s enhance or inhibit the action of other<unk> s in complex ways. They are different from hormones, which are also important cell signaling molecules. Hormones circulate in higher concentrations, and tend to be made by specific kinds of cells.<unk> s are important in health and disease, specifically in host immune responses to infection, inflammation, trauma, sepsis, cancer, and reproduction. The word comes from the ancient Greek language: cyto, from Greek κύτος, kytos, 'cavity, cell' + kines, from Greek κίνησις, kinēsis, 'movement'.
Cytokine
Lymphokine
Hormone
Inflammatory cytokine
Gastrointestinal hormone
Neurohormone
Xenohormone
Antibody