Figure 3

Sagittal section of stage 21 chick embryo immunostained with an anti-trypsin antibody. The olfactory nerve (ON, arrow) was immunoreactive for trypsin as were regions of the developing telencephalon (TEL). As a control, typsin protein was incubated with the anti-trypsin antibody for pre-absorption. This antigen/antibody complex was then used to immunostain sagittal sections of stage 21 chicks. Panel B demonstrates that pre-absorption eliminated all immunoreactivity in the head demonstrating the specificity of trypsin immunolocalization in experimental sections.