Appearance of F4/80-positive cells in fetal and neonatal lung. Tissues were stained, positive cells were quantified, and results are expressed for +/csfm^op (•) andcsfm^op/csfm^op (▴) after following matings of (A) +/csfm^op female ×csfm^op/csfm^op male and (B)csfm^op/csfm^op female ×+/csfm^op male mice as in Fig 2. Because of technical difficulties, Fig 6b includes only data through postnatal day 1. Where indicated, +/csfm^op differed fromcsfm^op/csfm^op at *P< .001. Results of multiple comparisons over time, where indicated, showed ^aP = .07 and^bP < .001 versus day13;^cP < .025 versus day 14; ^dP< .005 and ^eP < .001 versus day 15;^fP < .05 and ^gP < .001 verus day 18; and ^hP < .025 versus postnatal day 4, respectively.