Effect of eosinophil supernatants to promote neurite elongation is neutralized by anti-NGF antibody.

Eosinophils were suspended in RPMI 1640 medium supplemented with 10% DCS and incubated with medium alone or sIgA (20 μg/mL) + antihuman sIgA monoclonal antibody (1:10 000) + 25 ng/mL IL-5 (IL-5 + sIgA-IC) for 24 hours at 37°C. The replicate culture contained sIgA, antihuman sIgA monoclonal antibody, and IL-5 but no eosinophils. After culture, cell-free supernatants were collected. PC-12 cells were incubated with medium alone, 2 ng/mL NGF, supernatant of sIgA + anti-sIgA + IL-5 without eosinophils, supernatant of eosinophils cultured with medium alone, or supernatant of eosinophils cultured with sIgA + anti-sIgA + IL-5. Replicate eosinophil supernatants were treated with 100 ng/mL anti-NGF antibody or control goat IgG (cont). After 24 hours, the numbers of PC-12 cells with at least 2 neurites approximately 50 μm or longer were counted by using the dark field inverted microscope. Data show mean ± SEM from 5 experiments. * and ** denote significant difference from PC-12 cells incubated with medium alone (P < .05 andP < .01, respectively).