Regulated expression of germline antigen receptor genes in mast cell lines from the murine embryo.

Abelson murine leukemia virus-transformed cell lines derived from the earliest period of murine embryonic hematopoiesis express multiple characteristics of immature mast cells. We show here that both Ig and TCR-gamma genes are transcribed in some of these embryo-derived mast cell lines. Germline H chain V region transcripts are expressed constitutively, and germline Ig-mu and TCR-gamma constant region gene transcripts are induced in culture by the antiproliferative drug, BUdR. Coordinate with the up-regulation of the receptor gene transcripts, the B cell surface protein, B220, and IL-4 mRNA are also induced. The mechanism of action of BUdR was revealed by the observation that exogenous IL-4 alone induced both mu- and TCR transcripts in the transformed cells. Nontransformed mast cells cultured from embryonic liver and placenta also contain mu- and TCR-gamma transcripts. The expression of multiple Ag receptor genes in mast cells suggests that this cell type may be useful for our understanding of some of the early events of lymphoid development.