<prompt> CytokinesIncludes interleukinsProduced only insepsisAre polypeptide sHave highly specific action  <response>: Ref ananthanarayana 7e p143; Harrison 16e p 1915; Robbins 7e p202 Cytokines are a broad and loose category of small proteins 5-20 kDa that are impoant in cell signaling. Cytokines are peptides, and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrine signaling, paracrine signaling and endocrine s as immunomodulating agents The four-a-helix bundle family: member cytokines have three-dimensional structures with four bundles of a-helices. This family, in turn, is divided into three sub-families: the IL-2 subfamily the interferon IFN subfamily the IL-10 subfamily. 