EXTREMELY LOW-BIRTH-WEIGHT INFANTS HAVE LOWER FC-GAMMA-RIII (CD16) PLASMA-LEVELS AND THEIR PMN PRODUCE LESS FC-GAMMA-RIII COMPARED TO ADULTS

The purpose of this study was to determine whether decreased Fc gamma RIII expression on the PMN of extremely low birth weight infants (ELBW ) is due to decreased receptor synthesis or increased receptor sheddin g from the PMN surface. 42 ELBW, 12 larger infants and 14 adults were enrolled. Plasma and total cellular Fc gamma RIII were measured by ELI SA, and PMN Fc gamma RIII expression was measured by flow cytometry. E LBW PMN plasma membrane expression of Fc gamma RIII as measured by log mean channel fluorescence (5.00 +/- 1.98 vs. 10.68 +/- 1.61, p < 0.05 0) and plasma Fc gamma RIII levels were both lower (7.5 +/- 6.1 vs. 82 .4 +/- 64.8 nM, p < 0.05) than in adult controls. In follow-up studies , 14 ELBW (age = 29 +/- 14 days, range = 14-56 days) increased PMN exp ression of Fc gamma RIII (p < 0.001) but not plasma Fc gamma RIII. ELB W had lower total PMN-associated Fc gamma RIII than adults (2.3 +/- 0. 9 vs. 6.8 +/- 2.2 ng/10(6) PMN, p = 0.006). ELBW's PMN produce less Fc gamma RIII than adults' PMN, and expression of this receptor is devel opmentally regulated.