Suppression of mucosal mastocytosis by Nematospiroides dubius results from an adult worm-mediated effect upon host lymphocytes

Infections with the nematode Nematospiroides dubius fail to elicit mucosal mast cell (MMC) responses in the intestines of host mice, and suppress MMC responses generated by heterologous infection. Larval N. dubius have the capacity to prime for mastocytosis, and to elicit this response in primed mice during a challenge, but only if adult worms are prevented from developing, either by anthelmintic treatment or by irradiation of the larvae themselves. The suppressive effect of the adult stage was confirmed in experiments where such worms were implanted directly into the intestines of mice primed by exposure to irradiated N. dubius larvae or concurrently infected with Trichinella spiralis. Data on the mechanisms underlying this suppressive effect were obtained from experiments involving the adoptive transfer of mastocytosis by mesenteric lymph node cells (MLNC) from T. spiralis infected mice. When MLNC were taken from mice infected concurrently with both T. spiralis and N. dubius no enhanced mastocytosis was seen in recipients after challenge with T. spiralis. Exposure of MLNC from T. spiralis infected donors to the presence of adult N. dubius after transfer did not reduce the adoptively transferred response. The response was also unaffected when MLNC from adult N. dubius infected mice were simultaneously transferred with MLNC from T. spiralis donors. It is concluded that the suppressive effect of adult N. dubius upon the expression of mucosal mastocytosis acts upon the generation of lymphocytes capable of promoting the development of MMC from precursor cells.