Suppression of IgE responses in CD23-transgenic animals is due to expression of CD23 on nonlymphoid cells

Serum IgE is suppressed in CD23-transgenic (Tg) mice where B cells and some T cells express high levels of CD23, suggesting that CD23 on B and T cells may cause this suppression. However, when Tg B lymphocytes were compared w ith controls in B cell proliferation and IgE synthesis assays, the two were indistinguishable. Similarly, studies of lymphokine production suggested t hat T cell function in the Tg animals was normal. However, adoptive transfe r studies indicated that suppression was seen when normal lymphocytes were used to reconstitute Tg mice, whereas reconstitution of controls with Tg ly mphocytes resulted in normal IgE responses, suggesting that critical CD23-b earing cells are irradiation-resistant, nonlymphoid cells. Follicular dendr itic cells (FDC) are irradiation resistant, express surface CD23, and deliv er iccosomal Ag to B cells, prompting us to reason that Tg FDC may be a cri tical cell. High levels of transgene expression were observed in germinal c enters rich in FDC and B cells, and IgE production was inhibited when Tg FD Cs were cultured with normal B cells. In short, suppressed TgE production i n CD23-Tg mice appears to be associated with a population of radioresistant nonlymphoid cells. FDCs that interface with B cells in the germinal center are a candidate for explaining this CD23-mediated IgE suppression.