Inhibition of chicken adipocyte differentiation by in vitro exposure to monoclonal antibodies against embryonic chicken adipocyte plasma membranes

Specific monoclonal antibodies (MAb) against adipocyte precursor antigens w ere developed. These MAb identified adipocyte precursors and reduced their prominence in primary stromal-vascular (SV) cultures by complement-mediated cytotoxicity or by inhibition of differentiation. Binding of antibodies to chicken adipocyte precursors was confirmed by immunofluorescence visual ex amination following secondary exposure to fluorescein isothiocynanate-conju gated goat anti-mouse IgG. Cross-reaction of MAb with muscle, kidney, liver , fibroblasts, and other cell types not containing lipid droplets was not o bserved in primary cultures. Adipocyte precursors were obtained from 18-d c hick embryo adipose tissue by collagenase digestion to investigate compleme nt-mediated cytotoxicity of preadipocytes. Cultures were maintained in Medi um 199 with 5% fetal bovine serum (FBS) for 4 d. Subsequently, Medium 199 s upplemented with 10% chicken serum initiated adipocyte differentiation. At Day 5 postinoculation, individual or combinations of MAb were administered to preadipocyte cultures; rabbit complement was added 30 min later. After 1 d of incubation, four of the six individual MAb with complement significan tly (P < 0.05) reduced the number of fat cell clusters that developed by 40 to 60%. These MAb in the presence of complement also significantly (P < 0. 05) reduced mean cell width and apparent cell area or cell cluster area of lipid-containing cells. Neither MAb nor complement alone reduced fat cell c luster number, cell size, or cluster size. Treatment with pools of two and four MAb decreased the total amount of MAb protein required to reduce fat c ell cluster number. Four antibodies, alone or in combination, reduced fat c ell cluster development in a complement-dependent manner.