EFFECTS OF GROWTH-FACTORS ON CYTOKINE PRODUCTION IN SERUM-FREE CULTURES OF HUMAN THYMIC EPITHELIAL-CELLS

Human thymic epithelial cells (TEC) of medullary phenotype were cultur ed for 14 days in a growth factor-defined serum-free medium. The effec ts of added growth factors on cell numbers and the production of cytok ines were investigated by separate exclusion of the various growth fac tors from the medium. We found that hydrocortisone stimulated cell pro liferation but inhibited the differentiation of TEC and significantly reduced the production of interleukin-1alpha, interleukin-6 and granul ocyte-macrophage colony stimulating factor. Insulin was found to enhan ce the differentiation of TEC and the production of the three cytokine s. Transferrin and choleratoxin were found to inhibit cell proliferati on, but they did not affect production of the cytokines. Exclusion of epidermal growth factor, however, leads to cell death. We conclude tha t it is essential to exclude hydrocortisone from the medium to optimiz e production of cytokines, and that transferrin and choleratoxin seem to be unnecessary constituents in serum-free cultures of human TEC.