Possible Clues:

• Biological substance producible by eating nuts primarily
• Immunity stimulant
• It stimulates immune responses — tag nine (anag)
• Biological substance extractable from gentian
• Dope found on colonist, one that's given immunity
• From plant I generate toxin
• Get in a fantastic new biological substance
• … turn finally on eating? It'll help to get antibodies
• Opposing dope that could help towards fighting infection
• Immune response cause