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Infection and Immunity, January 2008, p. 380-390, Vol. 76, No. 1
0019-9567/08/$08.00+0     doi:10.1128/IAI.01043-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Surfactant-Associated Protein A Provides Critical Immunoprotection in Neonatal Mice

Departments of Pediatrics,¹ Anatomy and Cell Biology,² Pathology, University of Iowa, Carver College of Medicine, Iowa City, Iowa 52242³

Received 27 July 2007/ Returned for modification 4 September 2007/ Accepted 19 October 2007

The collectins surfactant-associated protein A (SP-A) and SP-D are components of innate immunity that are present before birth. Both proteins bind pathogens and assist in clearing infection. The significance of SP-A and SP-D as components of the neonatal immune system has not been investigated. To determine the role of SP-A and SP-D in neonatal immunity, wild-type, SP-A null, and SP-D null mice were bred in a bacterium-laden environment (corn dust bedding) or in a semisterile environment (cellulose fiber bedding). When reared in the corn dust bedding, SP-A null pups had significant mortality (P < 0.001) compared to both wild-type and SP-D null pups exposed to the same environment. The mortality of the SP-A null pups was associated with significant gastrointestinal tract pathology but little lung pathology. Moribund SP-A null newborn mice exhibited Bacillus sp. and Enterococcus sp. peritonitis. When the mother or newborn produced SP-A, newborn survival was significantly improved (P < 0.05) compared to the results when there was a complete absence of SP-A in both the mother and the pup. Significant sources of SP-A likely to protect a newborn include the neonatal lung and gastrointestinal tract but not the lactating mammary tissue of the mother. Furthermore, exogenous SP-A delivered by mouth to newborn SP-A null pups with SP-A null mothers improved newborn survival in the corn dust environment. Therefore, a lack of SP-D did not affect newborn survival, while SP-A produced by either the mother or the pup or oral exogenous SP-A significantly reduced newborn mortality associated with environmentally induced infection in SP-A null newborns.

Published ahead of print on 29 October 2007.

Editor: A. J. Bäumler