Hypothesis: neonatal necrotizing enterocolitis is caused by the acquisition of a pathogenic organism by a susceptible host infant.

The following hypothesis is offered for the etiology of neonatal necrotizing enterocolitis (NEC): that NEC is caused by the acquisition of a potentially pathogenic organism by a susceptible host infant. To test this hypothesis, serum IgM, IgG, IgA, C3, and C4, were measured in 11 neonates with NEC and 11 control infants matched for age and birth weight. Mean initial serum IgA was found to be significantly greater (p less than 0.05) in patients with NEC (8.4 mg/dl) than in control subjects (0.6 mg/dl). This difference persisted during a subsequent period of observation. There were no significant differences in initial concentrations of the other immunoglobulins or complement components. Serum IgM was noted to increase and serum IgG to decrease in both study groups during the period of observation. C3 rose minimally and C4 fell in patients with NEC. An explanation for this alteration in serum IgA concentration in infants with NEC is, at this time, speculative. However, this association, suggests that further evaluation of host susceptibility in this patient group may lead to a better understanding of this disorder.