A NEW IN-VITRO MODEL FOR STUDYING HUMAN T-CELL DIFFERENTIATION - T-H1T-H2 INDUCTION FOLLOWING ACTIVATION BY SUPERANTIGENS/

A new T-H1/T-H2 in vitro model for mechanistic studies and drug screen ing in human T cells was established working with ficoll-separated PBM Cs or elutriated lymphocytes cultured in serum-free medium. Human T ce lls could be kept viable and reactive in this medium for several month s. In this model, superantigens (SAs) were used to activate exclusivel y those T cell clones which were known to express specifically SA-bind ing V beta-chains of the T cell receptor. It was possible to identify the activated SA-specific T cells among the whole T cell population by using monoclonal antibodies against these V beta-chains and to follow responses involving receptor regulation and cytokine expression. The flow cytometric analysis revealed, that SA exposure caused an upregula tion of the IL-2 receptor selectively in the SA-specific subpopulation . Only the T cells of this subpopulation could be shifted towards T-H1 or T-H2 differentiation, which was determined by the distribution of IFN-gamma and IL-4 positive cells. Regulation of IFN-gamma could be de tected by now cytometry after 18 h and that of IL-4 on the third day o f cell culture. The differentiation status could be influenced by vari ous measures: TH1 shifts were achieved in the presence of IL-12 and an ti-IL-4, whereas, T-H2 shifts were induced more slowly with monocyte-r educed elutriated lymphocytes in the presence of IL-4, IL-6, anti-IL-1 2, 1 alpha,25-dihydroxy-vitamin-D-3 or combinations thereof. It was fo und that sialidase stimulated whereas TGF-beta and pentoxifylline supp ressed both kinds of T cell response. The T-H1/T-H2 differentiation pe rsisted for several weeks after primary activation if cells were expan ded in IL-2 containing serum-free culture medium. Therefore, this huma n T-H1/T-H2 in vitro model should be ideal for studying early and late events of infection, allergy, and autoimmunity as well as for investi gating the cellular interactions involved. In addition, the early dete ction of the response pattern makes this model potentially useful for drug screening. (C) 1998 Elsevier Science B.V. All rights reserved.