The proportion of lymphocytes bearing receptors for IgE (FcεR) markedly increased after infection of rats with Nippostrongylus brasiliensis (Nb). The FcεR-bearing lymphocytes from the infected animals bound more IgE-coated erythrocytes in rosette assay than FcεR-bearing cells from normal rats, suggesting that the number of FcεR per cell may also increase following the infection. In contrast, the number of IgE-receptors on peritoneal mast cells did not change after Nb infection. The increase in the proportion of FcεR-bearing lymphocytes in Nb-infected rats is probably due to an increased concentration of IgE in the environment. The proportion of FcεR-bearing cells in normal rat lymphocyte suspensions increased by culture of the cells with rat IgE of 1 µg/ml or higher concentration. Other immunoglobulins such as rat IgG, human IgE, or rabbit IgG failed to induce either FcεR-bearing cells or FcγR-bearing cells. It was also found that induction of Fc receptors by rat IgE is confined to FcεR. Kinetic studies on the induction of FcεR-bearing lymphocytes in vitro showed that the proportion of these cells in lymphocyte suspensions increased within 8 hr incubation with rat IgE but not within 4 hr. Evidence was obtained that both RNA synthesis and protein synthesis, but no DNA synthesis, are required for the induction of FcεR-bearing cells or the expression of the receptors on the cell surface.

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This work was supported by Research Grants AI-10060 from the United States Public Health Service, PCM78-10475 from the National Science Foundation, and the Lillia Babbitt Hyde Foundation. This paper is publication No. 343 from the O'Neill Laboratories at the Good Samaritan Hospital.

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