BMP-6 production in B cells
The fact that BMP-6 has been reported to act as an autocrine stimulator in chondrocytes [18] and ovarium [19], prompted us to investigate whether normal human B cells could produce BMP-6 upon stimulation. Ramos cells, which have been described to express BMP-6 mRNA endogenously [20], and the T cell line Jurkat, served as positive and negative controls, respectively. Endogenous BMP-6 mRNA levels in normal B cells were quantified by real-time RT-PCR after stimulation with anti-IgM for different time points. Interestingly, the up-regulation of BMP-6 mRNA was characteristic of an early-to intermediate inducible gene with maximal upregulation four hours after the addition of anti-IgM. The level of BMP-6 mRNA was back to baseline after 24 hours upon stimulation (Figure 10). Furthermore, both FCS and human AB-serum induced significant upregulation of BMP-6 mRNA (Figure 11). Interestingly, in a separate study we have found that normal human T cells do not express BMP-6 mRNA after activation (Sivertsen et al, manuscript in preparation). Next, we wanted to detect BMP-6 protein in normal B-cells and tested various commercially available antibodies. However, in our hands these anti-BMP-6 antibodies did only recognize the recombinant BMP-6 protein and not the native protein. 
