This transgene consists of the full length, 990-bp mouse interleukin 3 cDNA, in reverse (antisense) orientation, under control of the B19 parvovirus promoter and a T-cell dominant control region from the 3' end of the human CD2 gene. A human beta-globin gene segment including the 3' end of exon 2, all of intron 2 and exon 3, the polyadenylation signal and some 3' flanking DNA is present just downstream of the Il3 sequence. Interleukin 3 antisense RNA is detected by RT-PCR analysis in mature CD3+ T lymphocytes of transgenic animals both with lymphoproliferation and with no disease phenotype, in transgenic B220+IgM- pre-B cells, and in brains of both asymptomatic and neurologically affected transgenic mice. Il3 antisense transcripts are present in cultured splenocytes from asymptomatic transgenic mice following in vitro concanavalin A (ConA) stimulation, and ELISA of supernatants from these cultures demonstrates a 5-fold reduction in interleukin 3 secretion compared to similar cultures of control splenocytes. (J:107618)