Expression of Fcϵ receptors on activated human T lymphocytes

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Abstract
Our results clearly demonstrate that the low‐affinity receptor for IgE (FcϵR) is an activation antigen transiently expressed on a subpopulation of human T lymphocytes. It can be selectively induced by stimulation with certain antigens or lectins, but it is not found on resting T cells. The increased numbers of activated FcϵR+ T cells observed after stimulation of peripheral blood mononuclear cells (PBMC) from bee venom allergic patients with the specific allergen phospholipase A2 (PLA2) suggest that FcϵR+ T cells might very well be involved in the regulation of the human IgE response against the respective antigen. These results were obtained by the use of two monoclonal antibodies, M‐L25 and M‐L47, which were raised against the human low‐affinity FcϵR in our laboratory. After stimulation of PBMC with phytohemagglutinin a peak of 7,6 ± 6% FcϵR+ T cells was observed on day 3, with pokeweed mitogen of 0.8 ± 0.8% on days 2 and 3, and with concanavalin A of 0.6 ± 0.7% FcϵR+ T cells on day 2. Stimulation of PBMC with tetanus toxoid (TT) induced FcϵR on maximally 0.6 ± 0.8% of the total T cells (day 4), stimulation with purified protein derivative from tuberculin (PPD) on 0.2 ± 0.6% of the T cells (day 2). In contrast to these antigens, stimulation of PBMC from bee venom allergic patients with PLA2 induced as a peak 2.5 ± 2.5% of the total T cells to express FcϵR (day 5), although the stimulated T cell population was much smaller than with TT or PPD, as was shown by their stimulation indices. The allergen‐stimulated FcϵR+ T cells were exclusively T4+. The FcϵR‐expression index was determined, which for a specific antigen or lectin correlates the percentage of FcϵR+ T cells to the stimulated T cell population, respectively.