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Cloning of cDNA coding for low-affinity Fc receptors for IgE on human T lymphocytes
M Nonaka1, D K Hsu, C M Hanson
1Division of Immunology, Medical Biology Institute, La Jolla, CA 92037.
Using a cDNA probe corresponding to the membrane-bound form of the B cell receptor for IgE, we have isolated, sequenced, and expressed a cDNA clone which codes for a human T lymphocyte Fc epsilon R from HUT-78 cells. This T cell Fc epsilon R cDNA codes for 320 amino acid residues, and shows high homology to the B cell Fc epsilon R sequence. The major differences between this T cell and the B cell Fc epsilon R cDNA sequences are (i) a limited stretch of nucleotides at the 5' segment of the coding region which encodes a putative cytoplasmic region of the Fc epsilon R molecule and the untranslated 5' end; and (ii) an additional 64 bp segment in the untranslated 3' end containing two repeats in tandem with three existing repeats in the same region. The expression of Fc epsilon R on T lymphocytes may reflect involvement of the Fc epsilon R in regulation of IgE-mediated responses. The cytoplasmic difference implies functional activity of the Fc epsilon R in T lymphocytes that is mechanistically different from the Fc epsilon R of B lymphocytes.
Using a cDNA probe corresponding to the membrane-bound form of the B cell receptor for IgE, we have isolated, sequenced, and expressed a cDNA clone which codes for a human T lymphocyte Fc epsilon R from HUT-78 cells. This T cell Fc epsilon R cDNA codes for 320 amino acid residues, and shows high homology to the B cell Fc epsilon R sequence. The major differences between this T cell and the B cell Fc epsilon R cDNA sequences are (i) a limited stretch of nucleotides at the 5' segment of the coding region which encodes a putative cytoplasmic region of the Fc epsilon R molecule and the untranslated 5' end; and (ii) an additional 64 bp segment in the untranslated 3' end containing two repeats in tandem with three existing repeats in the same region. The expression of Fc epsilon R on T lymphocytes may reflect involvement of the Fc epsilon R in regulation of IgE-mediated responses. The cytoplasmic difference implies functional activity of the Fc epsilon R in T lymphocytes that is mechanistically different from the Fc epsilon R of B lymphocytes.