T-LYMPHOCYTE CLONES INITIATED FROM LESIONAL PSORIATIC SKIN RELEASE GROWTH-FACTORS THAT INDUCE KERATINOCYTE PROLIFERATION

To investigate whether growth factors derived from T cells in psoriati c lesions are able to stimulate keratinocyte growth, T-cell lines were initiated from lesional psoriasis skin and cloned by limiting dilutio n. Eight clones with good proliferative capacity out of 40 clones from one patient were stimulated. After 24 h, the conditioned medium was h arvested and the growth modulatory effect of the conditioned medium on keratinocytes was assessed. Seven of the eight T-cell clones stimulat ed keratinocyte growth to an extent ranging from 22% +/- 19 to 64% +/- 9 (mean +/- SD of three experiments) of maximal inducible keratinocyt e growth, and one T-cell clone had no effect (-5% +/- 2) on keratinocy te growth. Keratinocyte growth was also induced by T-cell clones obtai ned from two other patients. Several cytokines were tested in this sys tem to determine which T-cell growth factor may induce the keratinocyt e growth. None of the cytokines interferon-g, transforming growth fact or-beta, interleukin (IL)-2, IL-3, IL-4, IL-6, IL-8, or granulocyte-ma crophage colony stimulating factor alone was found to possibly be resp onsible for the T-cell - induced keratinocyte growth. Thus the nature of the T-cell keratinocyte growth-promoting stimulus remains to be elu cidated.