Appearance of F4/80-positive cells in fetal and neonatal liver. Tissues were stained for F4/80, a macrophage-specific marker, as described in the Materials and Methods and positive cells were quantified. Results are expressed as the mean ± SEM for+/csfm^op (•) andcsfm^op/csfm^op (▴) offspring after matings of (A) +/csfm^op female ×csfm^op/csfm^op male and (B)csfm^op/csfm^op female ×+/csfm^op male mice, respectively. Where indicated,+/csfm^op differed fromcsfm^op/csfm^op at *P < .001. Results of multiple comparisons over time, where indicated, showed^aP < .01 and ^bP < .001 versus day13; ^cP < .05, ^dP< .025, ^eP < .01, and ^fP< .001 versus day 14; ^gP < .01 and^hP < .001 versus day 15; ⁱP< .005 and ^jP < .001 versus day 18; and ^kP < .005 and ^lP < .001 versus postnatal day 1, respectively.