In Vivo and In Vitro Analysis of IL-10 in the NZB Leukemic Model.

BACKGROUND: The B-1 malignancy, CLL has been associated with a failure to undergo apoptosis and increased endogenous IL-10 production. This study was undertaken to identify IL-10 effects in the NZB murine model of CLL. MATERIALS AND METHODS: Antisense IL-10 was employed in vitro and in vivo to decrease IL-10 protein. Following treatment, cells were analyzed for alterations in cell cycle and RNA was studied for alterations in gene expression. Additional in vivo studies employed NZB mice in which the IL-10 gene was deleted. RESULTS: IL-10 (-/-) knockout NZB mice overwhelmingly failed to develop leukemia. In vitro antisense IL-10 treatment resulted in a G2/M block and apoptosis and in vivo treatment with antisense IL-10 increased the survival of mice. Microarray analysis indicated a significant role for IL-10 in cell cycle regulation via cdc25C up-regulation and decreased p47phox redox activity. CONCLUSION: In summary, IL-10 is a critical survival factor for malignant B cells via anti-apoptotic and cell cycle effects.

Mouse mammary tumor virus and the immune system.

Mouse mammary tumor virus (MMTV) is a nonacute transforming retrovirus that causes mammary tumors in susceptible strains of mice. Upon milk-borne transmission, B cells in the gut become infected and subsequently present a virus-encoded superantigen to cognate T cells. These T cells become activated and, in turn, stimulate neighboring lymphocytes, thereby establishing an infection-competent reservoir of lymphoid cells. During puberty and pregnancy, mammary epithelial cells actively divide, and viral transmission occurs from the lymphocytes that migrate to the mammary gland. Thus, MMTV utilizes the immune system to establish infection while simultaneously avoiding immune responses.

Neonatal infection with a milk-borne virus is independent of beta7 integrin- and L-selectin-expressing lymphocytes.

Mouse mammary tumor virus (MMTV) is acquired by neonates through milk and first infects lymphocytes in Peyer's patches. We show here that newborn mice lacking beta7 integrin or L-selectin were infected with MMTV at wild-type levels in both their lymphoid and mammary tissues. Superantigen-mediated activation and cognate T cell deletion were also unimpaired in both types of null mice. A large proportion of neonatal Peyer's patch lymphocytes in wild-type mice were beta7 and beta1 integrin low and both populations increased in response to MMTV infection. These results suggest that adhesion molecules other than beta7 integrin or L-selectin play a role in lymphocyte homing in the gut, peripheral lymph nodes and mammary gland in response to MMTV infection.