CALI of purified L1 inhibits its neurite-promoting activity. CALI directed against L1 using intra-L1 or 8D9 resulted in marked inhibition of the percentage of cells with neurites.Lanes A–D show CALI of mouse L1 substrate using MG-labeled intra-L1: lane A, no treatment; lane B, laser irradiation without MG-labeled antibody; lane C, MG-labeled intra-L1 without laser irradiation; lane D, MG-labeled intra-L1 with laser irradiation. Lanes E–H show CALI of chick L1 substrate using MG-labeled 8D9:lane E, no treatment; lane F, laser irradiation without MG-labeled antibody; lane G, MG-labeled 8D9 without laser irradiation; lane H, MG-labeled 8D9 with laser irradiation. Lanes I–K show that laser irradiation using MG-8D9 did not affect neurite outgrowth-promoting activity of laminin. Lane I, No treatment; lane J, irradiation without MG-labeled 8D9;lane K, MG-labeled 8D9 with laser irradiation. The data are representative of three experiments with n > 100 neurons for each treatment.