Table 1. Injection of SP-A into all amniotic sacs of one uterine horn of 15 dpc pregnant mice causes preterm labor whereas injection of antibody to SP-A delays labor
No. of mice
Injection Preterm parturition Term parturition Delayed parturition
SP-A (3 μg per sac) 14/17 (3.0 ± 0.5 days preterm) 3/17
SP-A-depleted eluate 4/4
LPS (9 fg per sac) 4/4
SP-A antibody 6/6 (27.5 ± 9.7 h postterm)
Nonimmune rabbit IgG 3/3
  • SP-A (3 μg per sac) i.a. injected into 15 dpc mice caused preterm parturition in 14 of 17 mice. To control for unknown contaminants in the SP-A preparation, 15 dpc mice were i.a. injected with an SP-A-depleted preparation (n = 4). These mice delivered at term. To control for levels of LPS remaining in the SP-A preparation, 15 dpc mice were i.a. injected with LPS (9 fg of LPS per sac) (n = 4); these mice delivered at term. Endogenous AF levels of SP-A were immunodepleted by i.a. injection of 15 dpc mice with SP-A antibody (150 ng per sac) (n = 6). These mice delivered at least 24 h late. To control for nonspecific effects of rabbit IgG, 15 dpc mice were i.a. injected with 150 ng of rabbit nonimmune IgG (Sigma) per sac (n = 3); these mice delivered at term.