To determine the mechanism(s) of diminished, stimulated, and directed migration of neonatal (N) polymorphonuclear leukocytes (PMN), chemotactic factor (CF) sensory and PMN effector functions were studied in healthy N and adult or maternal controls (C). N PMN demonstrated high affinity binding for N-formyl-methionyl-leucyl-[3H]phenylalanine (fMLP), which was saturable between 40 and 100 nM as observed with C PMN. The kinetics of binding and the characteristics of dissociation of binding by N PMN were equivalent to control PMN. Both "threshold" and "peak" concentrations (1 and 10 nM, respectively) of fMLP effected comparable PMN chemiluminescence among neonates and controls. An equivalent threshold concentration (0.05 nM) of fMLP effected N and C PMN shape change in suspension, and a maximally effective concentration (5 nM) induced comparable bipolar configuration, although uropod formation was only 38 +/- 8% of N PMN, compared with 73 +/- 11% of C PMN (P less than 0.01). Striking abnormalities of N PMN adherence were identified: mean +/- SD base-line (unstimulated) N adherence values (39 +/- 8%) were equal to C (38 +/- 9%), but diminished increments in response to single CF stimuli were noted among N (fMLP: 42 +/- 7% (N), 70 +/- 11% (C); C5a: 41 +/- 6% (N), 68 +/- 6% (C); BCF: 41 +/- 6% (N), 63 +/- 9% (C), P less than 0.01 for each CF). On sequential exposure to increasing concentrations of CF N PMN failed to demonstrate expected decreased adherence values; sequential stimuli with fMLP (0.1 nM, 10 nM) or C5a (8 microgram protein/ml, 32 microgram protein/ml) effected mean +/- 1 SD values of 51 +/- 9% (N), 30 +/- 9% (C), and 34 +/- 10 (N), 48 +/- 14% (C), respectively. As demonstrated with a latex bead-binding technique, N PMN failed to redistribute adhesion sites to the cell's tail under the same experimental conditions; in 21 N samples studied, restricted unipolar binding occurred in 33 +/- 8% (fMLP) or 37 +/- 7% (C5a) of PMN in contrast to C values of 70% (fMLP), or 71% (C5a), P less than 0.001. Similar findings were observed when PMN were preincubated with colchicine (25 microgram/ml); expected diminished adherence scores (compared with base-line values) were demonstrated with C PMN but not with N cells, P less than 0.01. Additionally colchicine-induced redistribution of adhesion sites as was observed with C samples (72 +/- 14% unipolar binding) was significantly (P less than 0.001) less among N PMN (31 +/- 11% unipolar binding). These investigations indicate that CF sensory mechanisms of N PMN are normal, compared with healthy adult or maternal controls. Diminished stimulated locomotion of the N PMN may be functionally related to reduced modulation of cell adhesiveness by chemotactic stimulation.