ANTIGEN-PRESENTING HUMAN T-CELLS AND ANTIGEN-PRESENTING B-CELLS INDUCE A SIMILAR CYTOKINE PROFILE IN SPECIFIC T-CELL CLONES

One of the factors that may influence the cytokine secretion profile o f a T cell is the antigen-presenting cell (APC). Since activated human T cells have been described to express major histocompatibility compl ex (MHC) class II molecules as well as costimulatory molecules for T c ell activation, like e.g. ICAM-1, LFA-3 and B7, they might play a role as APC and be involved in the regulation of T-T cell interactions. To define further the role of T cells as APC we tested their capacity to induce proliferation and cytokine production in peptide- or allospeci fic T cell clones and compared it with conventional APC, like B lympho blasts (B-LCL) or HTLV-1-transformed T cells, or with non-classical AP C, like activated keratinocytes or eosinophils. CD4+, DP-restricted T cell clones specific for a tetanus toxin peptide (amino acids 947-967) and CD4+, DR-restricted allospecific T cell clones produced interleuk in (IL)-2, IL-4, tumor necrosis factor-alpha and interferon-gamma (IFN -gamma) after phorbol 12-myristate 13-acetate and ionomycin stimulatio n and a more restricted cytokine pattern after antigen stimulation. Do se-response curves revealed that the antigen-presenting capacity of ac tivated, MHC class II+, B7+ T cells was comparable to the one of B-LCL . Both APC induced the same cytokine profile in the T cell clones desp ite a weaker proliferative response with T cells as APC. Suboptimal st imulations resulted in a lower IFN-gamma/IL-4 ratio. Cytokine-treated, MHC class II+ keratinocytes and eosinophils differed in the expressio n of adhesion molecules and their capacity to restimulate T cell clone s. The strongly ICAM-1-positive keratinocytes induced rather high cyto kine levels. In contrast, eosinophils, which express only low densitie s of MHC class II and no or only low levels of adhesion molecules (B7, ICAM-1 and LFA3), provided a reduced signal resulting in a diminished IFN-gamma/IL-4 ratio. We conclude that non-classical APC differ in th eir capacity to restimulate T cell clones, whereby the intensity of MH C class II and adhesion molecules (B7, ICAM-1) expressed seems to dete rmine the efficacy of this presentation.