Interleukin-4 (B-cell stimulatory factor-1) can enhance or antagonize the factor dependent growth of hematopoietic progenitor cells - Rennick, D; Yang, G; Muller-Sieburg, C; Smith, C; Arai, N; Takebe, T; Gemmel, T (Proc Natl Acad Sci USA, 1987)