CHAPTER 35, FIG URE 24 Secondary structural features of cytokines. (A) IFN-a2A (shown with both end and
side views of the 5 a helices). (B) IL-4, showing the a helices from both end and side views. This group of cytokines
is characterized by the 4-6 distinct
helices that form the protein “backbone.” (C) IL-1
showing the fS-sheet structure
that is characteristic of this group of cytokines.