Bioactivity of PRL of culture supernatants of THP-1 monocytes activated with LPS. A, Western blot analysis of PRL with supernatants of THP-1 monocytes activated with LPS 1 μg/ml and harvested at different times after treatment. B, proliferation bioactivity in concentrated supernatants (24X) was assayed in Nb2 cell cultures after addition of different volumes: 5, 10, 20 and 45 μl; and C, including anti-PRL mAb E-9 (dashed line) for inmunoinhibition. Proliferation expressed as OD550nm (left Y axis) or extrapolated and expressed in picograms (right Y axis) are shown. All experiments were performed in triplicate and data are expressed as mean ± SD (n = 3). Significance is defined as p<0.05*, p<0.001**, p<0.0001*** versus control.