The third version is involved in regulating mast cell proliferation, while the fourth is thought to 
The third version is involved in regulating mast cell proliferation, while the fourth is thought to be a B-cell growth factor.  The most useful is probably number 2, which stimulates production of other cytokines, colony stimulating factor, and gamma interferon, and has been researched as an anticancer agent.  FTP, identify this class of cytokines which serve to interact with and mediate leukocyte behavior.
The third version is involved in regulating mast cell proliferation, while the fourth is thought to be a B-cell growth factor.  
interleukins