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 were 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 examination following secondary exposure to fluorescein isothiocyanate-conjugated goat antimouse IgG. Cross-reaction of MAb with muscle, kidney, liver, fibroblasts, and other cell types not containing lipid droplets was not observed in primary cultures. Adipocyte precursors were obtained from 18-d chick embryo adipose tissue by collagenase digestion to investigate complement-mediated cytotoxicity of preadipocytes. Cultures were maintained in Medium 199 with 5% fetal bovine serum (FBS) for 4 d. Subsequently, Medium 199 supplemented 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 significantly (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 cluster 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 cell cluster number. Four antibodies, alone or in combination, reduced fat cell cluster development in a complement-dependent manner.