Heat shock proteins (HSPs) are ubiquitously expressed in all organisms. The HSPs fall into five general families: HSP105, HSP90, HSP70, the low molecular weight HSPs, and the immunophilins. The HSP105 (also called HSP110) family is composed of HSP105, Apg-1 and Apg-2. The HSP90 family consists of HSP90α, HSP90β and GRP94. The HSP70 family is comprised of HSP70, HSC70, GRP78 and GRP75. The low molecular weight HSPs includes HSP10, HSP25, HSP27 and HSP32. HSP56 and FKBP12 are immunophilins and bind to immunosuppressive drμgs.