Influence of prolactin on the differentiation of mouse B-lymphoid precursors

Development and activation of immune cells are submitted to hormonal influe nces, as illustrated by the roles of corticosteroids in thymus, pregnancy-r elated estrogens in B-cell development, or prolactin (PRL) on T-cell genera tion and function. We have analyzed the putative role of PRL in B lymphopoi esis and differentiation. We chose as an experimental model the interleukin (IL)-3 dependent BaF-3 pro-B cell line, which was transfected with the rat long form of the PRL receptor (PRL-R) and transferred from IL-3- to PRL-en riched media, When stimulated with PRL, the PRL-R transfectants underwent s ome changes characteristic of B-cell differentiation: (a) IL-2R alpha chain became positively controlled by PRL; (b) antiapoptotic Bcl-2 protein was i nduced by PRL in a dose-dependent manner; and (c) transcription of the pre- B cell receptor encoding the lambda 5 gene was strongly up-regulated. We at tempted to evaluate the differentiation-promoting activity of PRL in more p hysiological conditions, and the presence of PRL-R in bone marrow B-cell pr ecursors was revealed, Furthermore, PRL promoted significant expansions of defined B-lineage cell populations in short-term bone marrow cell cultures. These findings suggest that PRL, in collaboration with other cytokines and hormonal influences, modulates B-cell development.