Decreased fat content and increased lean in pigs treated with antibodies to adipocyte plasma membranes.

: Antibodies were prepared in sheep against purified plasma membranes from pig adipocytes. Western (immuno) blotting revealed reactions of the antisera with a large number of proteins in adipocyte plasma membranes but remarkably few in plasma membranes from muscle, kidney, liver, lung, brain, spleen, and erythrocytes. This illustrated the high degree of specificity the serum had for adipose tissue. When injected into localized subcutaneous sites such antisera were able to cause considerable adipocyte destruction, which resulted in complete loss of adipose tissue from the site for > or = 14 wk. This cell destruction was probably mediated in part by lymphocytic infiltration. Subcutaneous injections were of limited use because of the localized nature of the effects, but, when treatment was administered intraperitoneally, systemic effects were produced that resulted in a 30% reduction in backfat thickness in the region of the last rib and a 25% reduction in fat content of fore- and hind-loin joints that resulted in a significant increase in the percentage of lean tissue. Total feed intake, live weight gain, hot carcass weights, and dressing percentage were unaffected. These results demonstrate the potential for producing long-term reductions in body fat in pigs by an immunization technique that may also provide the unexpected, potential benefit of increased lean deposition. This suggests that fat deposition per se exerts a restrictive influence on lean carcass development.