DEVELOPMENT OF BASOPHILS IN MONGOLIAN GERBILS - FORMATION OF BASOPHILIC CELL CLUSTERS IN THE BONE-MARROW AFTER NIPPOSTRONGYLUS-BRASILIENSISINFECTION

Development of basophilic leukocytes was studied in the Mongolian gerb il, Meriones unguiculatus, after infection with the nematode Nippostro ngylus brasiliensis. After infection, peripheral blood basophilia deve loped and peaked at 2 weeks. In bone marrow sections, numbers of alcia n blue(+)/safranine(-) basophilic cells were increased. These cells di d not bind berberine sulfate and were clearly distinguishable from the bone marrow-resident mast cells, safranine(+) and berberine sulfate(). Alcian blue(+)/safranine(-) cells were identified by electron micro scopy as basophilic myelocytes in various stages of maturation. In the early period of infection, these cells had round-to-oval granules wit h a homogenous electron-dense matrix, a well-developed Golgi apparatus and rough endoplasmic reticulum, and a nonsegmented nucleus. By enzym e cytochemical analysis, intense peroxidase activity was demonstrated in all of the specific granules as well as in the rough endoplasmic re ticulum and Golgi apparatus. Two weeks after infection, the number of bone marrow basophilic cells further increased, forming distinct clust ers or islands composed of up to 100 cells each. On electron micrograp hs, the basophilic cells in these clusters appeared to be late-stage b asophilic myelocytes, ie, having an increased number of granules, a le ss-conspicuous Golgi apparatus and rough endoplasmic reticulum, a hors eshoe-shaped-to-lobulated nucleus, and reduced peroxidase activity. Eo sinophils and mast cells were rarely found in the basophilic cell clus ters. Four weeks after infection, the clusters had disappeared. These results show that gerbil basophilic myelocytes tend to form cell clust ers in the bone marrow during their active proliferation. The comparat ive paucity of other cell lineages in basophilic cell clusters suggest s that basophilia is generated from differentiation/proliferation of p recommitted basophil progenitors independently from cells of other lin eages.