Senescent jejunal mast cells and eosinophils in the mouse preferentially translocate to the spleen and draining lymph node, respectively, during the recovery phase of helminth infection

Because mice infected with Trichinella spiralis experience a pronounced, bu t transient, mastocytosis and eosinophilia in their intestine, this disease model was used to follow the fate of senescent T cell-dependent mast cells (MCs) and eosinophils. Very few MCs or eosinophils undergoing apoptosis we re found in the jejunum during the resolution phase of the infection, even though apoptotic MCs were common in the large intestine. Although the mesen teric draining lymph nodes contained large numbers of apoptotic eosinophils , MCs were rarely found at this location. During the recovery phase, large numbers of MCs were present in the spleen, and many of these cells possesse d segmented nuclei. These splenic MCs were not proliferating. Although MCs from the jejunum and spleen of noninfected mice failed to express mouse MC protease (mMCP) 9, essentially all of the MCs in the jejunal submucosa and spleen of T, spiralis-infected mice expressed this serine protease during t he recovery phase. The MCs in the jejunum expressed mMCP-9 before any mMCP- 9-containing cells could be detected in the spleen. The fact that mMCP-9-co ntaining MCs were detected in splenic blood vessels as these cells began to disappear from the jejunum supports the view that many jejunal MCs translo cate to the spleen during the recovery phase of the infection. During this translocation process, some senescent jejunal MCs undergo nuclear segmentat ion. These studies reveal for the first time different exit and disposal pa thways for T cell-dependent eosinophils and MCs after their expansion in th e jejunum during a helminth infection.