ABSTRACT
Administration of high dose cyclophosphamide (CY, 200 mg/kg body weight) to adult mice induces transient, nonspecific suppressor activity in the spleen of treated animals. Characterization of the CY-induced natural suppressor (NS) cells which inhibit mixed lymphocyte reactions revealed a heterogeneous population of lymphocytes expressing the CD8 T cell marker and the B220 B cell marker, as well as cells bearing the granulocyte-monocyte marker CD11b. On a cell per cell basis the most potent of these suppressors were found to be positive for CD11b. Inhibitory activity was also detected in the CD8-, CD11b-, B220- compartment of CY-spleen, suggesting the presence of null NS cells. The fact that several phenotypically distinct cell populations contribute to the overall inhibitory effect of CY-spleen cells indicates that natural suppression defines an activity rather than a specific cell type. Interestingly, NS activity was observed to reside solely within the fraction of CY-spleen that is agglutinable with soybean agglutinin or wheat germ agglutinin, suggesting that expression of receptors for these plant lectins is a universal characteristic of CY-induced NS cells, regardless of their lineage. CY-spleen cell-mediated suppression of lymphoproliferative responses was found to be partially dependent on DNA synthesis and totally dependent on protein synthesis, but did not require cell-cell contact, indicating the production of soluble suppressor factor(s).
Subject(s)
Cyclophosphamide/pharmacology , Spleen/cytology , T-Lymphocytes, Regulatory/drug effects , Animals , Cells, Cultured , Flow Cytometry , Immunophenotyping , Lymphocyte Activation/drug effects , Lymphocyte Culture Test, Mixed , Mice , Mice, Inbred CBA , Mice, Inbred DBA , Mitomycin/pharmacology , Puromycin/pharmacology , Spleen/drug effectsABSTRACT
We report epidermal growth factor (EGF)-like and epidermal growth factor receptor (EGFR)-like immunoreactivity in the buccopharyngeal mucous glands of Xenopus laevis larvae. EGF-like immunostaining was heaviest at the apices of the secretory cells of these glands. Immunostaining for EGFR-like protein was also observed in the mucosal lining of the alimentary tract. This staining was heaviest in cells lining the foregut but was almost absent in cells from the hindgut. A potential role for an orally secreted EGF homologue in anuran amphibians is discussed. Wassersug (1986) hypothesized the existence of a metamorphic inhibitory agent, produced by larval buccopharyngeal mucous glands, which could indirectly link food ingestion to the endocrine control of metamorphosis. The presence of EGF-like immunoreactivity in the oral mucous glands of X. laevis larvae, as well as the presence of EGFR-like immunoreactivity in the gut wall of this tadpole, satisfies many of the criteria for Wassersug's regulatory agent. It remains to be shown that EGF (or an anuran EGF homologue) has a direct inhibitory effect on anuran metamorphosis when administered via an orogastric route.
