OBJECTIVE: To review the main aspects of fetal immune development focusing on the host defenses of extremely preterm infants against bacterial pathogens, and describing the possibilities of immunotherapeutic intervention for the prevention of neonatal nosocomial sepsis. SOURCES OF DATA: Electronic search of MEDLINE database for articles published in the last 15 years. Those with relevant information regarding the target issue were selected. SUMMARY OF THE FINDINGS: Immunity of extremely preterm infants is deficient due to skin fragility, insufficient complement system components, decreased bone marrow neutrophil storage pool, and lower chemotaxis, adherence, deformability, and neutrophil enzyme activities. Further limitations are found at NK cell-mediated cytotoxicity, T cell proliferation and cytokine production, B and T cell cooperation, and antibody synthesis by B lymphocytes. No definitive benefits of interventions for enhancing the immune function, such as the use of intravenous immunoglobulin or myeloid colony-stimulating factors, have been demonstrated. CONCLUSION: As a consequence of the immaturity of several immune components, extremely preterm infants are highly susceptible to nosocomial infections. The very limited possibilities for intervention in this system require the control of extrinsic factors for the prevention of nosocomial sepsis in these infants.
Premature infant; immunity; nosocomial infection; immunotherapy
