Antibodies against the spondin domain inhibit sensory neurite outgrowth on axotomized sciatic nerve. A, B, E14 DRG ganglia were cultured on cryosections of lesioned adult rat sciatic nerve (3 weeks after axotomy) for 48 hr with either preimmune serum (A) or 100 μg/ml R5 immunoglobulin (B). Note that the addition of R5 immunoglobulin results in the tighter grouping of neurites and reduces the extent of neurite outgrowth from the explant. C, D, E14 DRG ganglia were cultured in a three-dimensional collagen gel for 24 hr. The extent of neurite outgrowth with 100 μg/ml R5 IgG (D) or with preimmune Ab (C) is similar. E, Summary plot of the effect of R5 immunoglobulin on neurite outgrowth on cryosections of axotomized sciatic nerve. Each dot represents the area occupied by the neurites emerging from one DRG. Theboxes enclose 50% of the results; the horizontal lines above and under the box enclose 90% of the results; the horizontal line within thebox is the median. The difference among the groups was assessed via the Kruskal–Wallis test (Siegal, 1956), which was statistically significant (p value<0.001).