Divergent cell-specific effects of activin-A on thymocyte proliferation stimulated by phytohemagglutinin, and interleukin 1beta or interleukin 6 in vitro

Cytokine. 2000 Jun;12(6):595-602. doi: 10.1006/cyto.1999.0597.


Activin-A is a member of the transforming growth factor-beta (TGF-beta) cytokine family. Based on studies in several cell systems, activin-A has been postulated to be a specific inhibitor of the actions of the inflammatory cytokine, interleukin 6. In cultures of adult rat thymocytes, activin-A inhibited sub-optimal phytohemagglutinin-induced and interleukin 1beta-stimulated proliferation, as measured by [(3)H]-thymidine incorporation in vitro. In contrast with TGF-beta1, which exerted similar inhibitory effects on thymocyte proliferation, activin-A activity was reduced by increasing the concentration of phytohemagglutinin or addition of the reducing agent, beta-mercaptoethanol. Both activin-A and TGF-beta1 inhibited the in vitro production of interleukin 6 by thymocytes in the presence of phytohemagglutinin and interleukin 1beta. In the presence of exogenous interleukin 6, however, both activin-A and TGF-beta1 stimulated thymocyte proliferation. These data suggest that activin-A inhibits thymocyte growth and differentiation, at least in part, by inhibiting endogenous production of interleukin 6, but stimulates thymocyte growth when exogenous interleukin 6 is present in vitro. These data indicate that activin interacts with other cytokines to exert complex regulation of T cell development, and is not an inhibitor of interleukin 6 action in all cell systems.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activins
  • Animals
  • Cell Division / drug effects
  • Cell Line
  • Cells, Cultured
  • Growth Substances / pharmacology
  • Humans
  • Inhibins / pharmacology*
  • Interleukin-1 / pharmacology*
  • Interleukin-6 / pharmacology*
  • Interleukin-6 / physiology
  • Kinetics
  • Lymphocyte Activation / drug effects*
  • Male
  • Mercaptoethanol / pharmacology
  • Phytohemagglutinins / pharmacology*
  • Rats
  • Rats, Inbred Strains
  • Recombinant Proteins / pharmacology
  • T-Lymphocytes / cytology
  • T-Lymphocytes / drug effects
  • T-Lymphocytes / immunology*
  • Transforming Growth Factor beta / pharmacology*


  • Growth Substances
  • Interleukin-1
  • Interleukin-6
  • Phytohemagglutinins
  • Recombinant Proteins
  • Transforming Growth Factor beta
  • Activins
  • Inhibins
  • Mercaptoethanol