MOUSE MAMMARY-TUMOR VIRUS AND ITS INTERACTION WITH THE IMMUNE-SYSTEM

Mouse mammary tumor virus (MMTV) is a retrovirus that is transmitted t hrough milk to offspring. Gut-associated B cells are the first cells t o be infected during virus transmission, and these cells present a vir us-encoded superantigen to cognate T cells. This allows MMTV to replic ate and amplify in activated lymphocytes and ultimately results in vir us transmission to the mammary epithelial cells. Because the superanti gen has profound effects on the T cell repertoire and because MMTV rep licates in lymphoid cells, loss of immune response to the virus may al so play a role in its ability to persist within its host. Transcriptio nal control of MMTV expression also plays an important part in this pa thway and DNA recognition sequences for transcription factors that all ow its expression in lymphoid organs and mammary epithelia are encoded within the virus. Thus, this virus has evolved to take maximum advant age of its host's biology.