You should use Fc block (anti-CD16/CD32) to inhbit the binding of the Fc region in the IL-10 antibody to the Fc receptors on the surface of B-cells. This is also important for any surface staining in any cell expressing Fc receptors.

Thanks. So do you need to use Fc blocking antibodies if you do experiments using monocytes? Also do you have to use Fc blocking antibodies for intracellular staining only? Wont other antibodies bind to it?

Yes, you need to use the Fc blocking antibodies with myeloid cells or B cells for both intracellular and surface stainings.