Inhibitory effects of concurrently present 'normal' Nippostrongylus brasiliensis worms on expulsion of 'damaged' worms and associated goblet cell changes in rats.

Nippostrongylus brasiliensis worms obtained from the stable phase of a primary infection ('normal' worms) are able to establish and survive in naïve recipient rats into which they have been adoptively transferred, whereas those obtained at the time of expulsion ('damaged' worms) are rapidly expelled. Expulsion is associated with quantitative/qualitative goblet cell changes. Thus, N. brasiliensis adult worms seem to stimulate the expulsion process only after being 'damaged' by the host's immunity, whereas it is possible that 'normal' worms may inhibit the expulsion process. To see whether 'normal' worms have such inhibitory effects, the fate of concurrently implanted 'normal' and 'damaged' worms was examined with reference to goblet cell changes in the intestine. By using either male or female worms as 'normal' or 'damaged' populations, it was possible to determine the origin of worms remaining in the intestine. The results show that not only 'normal' worms but also 'damaged' worms, which would normally be expelled, remained in the intestines of the recipients on Day five. Goblet cell hyperplasia and alteration of terminal sugars of mucins, which was induced within five days after implantation of 'damaged' worms, were completely inhibited by the concurrent presence of 'normal' worms. The inhibitory effects of 'normal' worms were destroyed when they were killed by heating before implantation. Possible mechanisms leading to expulsion of N. brasiliensis are discussed.