Immunoglobulin subclass concentration in preterm infants treated prophylactically with different intravenous immunoglobins.

The most immature infants have critically low concentrations of all immunoglobulin G (IgG) subclasses, associated with a higher risk for pyogenic, respiratory, and meningeal infection. Selective IgG subclass deficiency is an established indication for intravenous immunoglobulin (IVIG) substitution. However, considering that therapeutic efficacy of IVIG is dependent on its pharmacokinetics, we studied peak and trough IgG subclass serum levels during the neonatal period (28 days) in a group of 34 healthy preterm babies (30.2 +/- 2 weeks gestational age (GA) and 1065 +/- 210 g birthweight (BW) treated prophylactically with three daily standard doses of two different IVIG preparations: Sandoglobulin (SG) (0.5 g/kg/day) and Pentaglobin (PG) (5 mL/kg/day). IgG subclass levels were assayed by radioimmundiffusion (RID) before treatment (day 1) and at days 3, 5, 7, 14, and 28 of life. Statistical analysis was performed by paired t test. In the first week of life only (days 3, 5, 7), for both IVIG preparations, subclass levels were higher than pretreatment values: IgG1, 4.6 +/- 1.7 versus 5.6 +/- 1.6 g/L; IgG2, 1.6 +/- 0.8 versus 2.1 +/- 0.6 g/L; IgG3, 0.2 +/- 0.7 versus 0.3 +/- 0.1 g/L; IgG4, 0.3 +/- 0.1 versus 0.9 +/- 0.1 g/L (p < 0.05). During this time (7 days) IgG2 levels were higher in the SG group and IgG4 was higher in the PG group (p < 0.05). This study shows pretreatment IgG subclass levels 14 days after treatment and different patterns, depending on the used preparation. We conclude that prospective clinical trials should include the study of target serum levels and timing of IVIG administration not only for IgG but also for IgG subclasses.