OBESITY MINIMIZES THE IMMUNOPOTENTIATION OF FOOD RESTRICTION IN OB OBMICE/

The objective of this study was to investigate food restriction-relate d changes in several indices of immune competence in young (11 wk old) and adult (33 wk old) female lean (+/?) and obese (ob/ob) C57BL/6J mi ce. Body weight accumulation, tail length accretion and organ weights were more severely curtailed by food restriction in obese mice than in lean mice. Tail collagen denaturation time increased with age, althou gh the magnitude was greater in obese mice, and this change was minimi zed by food restriction. Splenocyte mitogen responses were generally n ot altered with age in lean or obese mice, whereas food restriction au gmented these responses in lean mice while having no effect or reducin g them in obese mice. The concanavalin A and phytohemagglutinin respon ses of splenocytes from young and adult obese mice were greater than t hose for lean mice, whereas the bacterial lipopolysaccharide response was elevated only in adult obese vs. lean mice. Flow cytometric analys is of splenocytes revealed an increase in Thy-1(+) cells with food res triction vs, freely fed obese and lean mice, with a proportional decre ase in Ig(+) cells. Percentages of CD4(+) and CD8(+) cells increased w ith food restriction in both lean and obese mice. These results sugges t that genetic obesity largely eliminates the immunopotentiating effec ts of food restriction, although the rate of ''aging'' may be reduced by food restriction.