Analysis of mannose receptor regulation by IL-4, IL-10, and proteolytic processing using novel monoclonal antibodies

The study of the murine macrophage mannose receptor (MR) has been hampered by the lack of specific reagents. We have generated and characterized novel anti-MR monoclonal antibodies and used them to analyze MR expression in primary mouse macrophages (MO). In BioGel- and thioglycollate-elicited MO, interleukin (IL)-4 up-regulated total cell-associated MR (cMR), correlating with enhanced surface expression. We investigated the influence of IL-10, a well-characterized deactivator of MO function, on MR levels and observed that it had a similar effect to IL-4. In both cases, enhanced cMR levels translated into increased production of the soluble form of the receptor (sMR). We have demonstrated the presence of sMR in cultures of stable non-MO transductants expressing full-length MR, indicating that the proteolytic activity responsible for cMR cleavage is not MO-restricted. These data support a role for the MR in T helper cell type 2 cytokine-driven, immune responses and suggest a non-MO contribution to sMR production in vivo.