Abilities of human oligodendroglial cells and mouse Schwann cells to phagocytose Mycobacterium leprae and other mycobacteria.

Human oligodendroglial KG-1-C cells derived from human cerebral mixed glioma and mouse Schwann cells derived from dorsal root ganglion were studied with respect to their abilities to phagocytose various mycobacteria, especially Mycobacterium leprae, and other microorganisms. KG-1-C cells phagocytosed M. leprae at a markedly higher rate than BALB/3T3, BHK 21, HeLa S3, mKS-A TU-7, XC, TSV-5, N-18, and Schwann cells but at a lower rate than peritoneal macrophages. Schwann cells also exhibited substantial phagocytic ability against M. leprae, and their phagocytic rate against M. leprae was much higher than that of N-18 cells, derived from neurons. KG-1-C and Schwann cells phagocytosed mycobacteria other than M. leprae, and their phagocytic patterns with various mycobacteria were similar, thereby suggesting that their abilities to phagocytose mycobacteria were based on the same cellular mechanism. The time course of phagocytosis of M. leprae by KG-1-C cells markedly differed from that by macrophages, indicating differences in the cellular mechanisms of M. leprae phagocytosis. KG-1-C cells also ingested microorganisms other than acid-fast bacilli, such as Staphylococcus aureus, Listeria monocytogenes, Bacillus subtilis, and Escherichia coli but not Candida albicans. They also phagocytosed latex beads (0.8-micron diameter) but not sheep erythrocytes. Microscopically, most mycobacterial cells were ingested in the perikaryon of KG-1-C cells and Schwann cells.

Mechanisms of phagocytosis of Mycobacterium leprae and other mycobacteria by human oligodendroglial cells.

The mechanisms by which human oligodendroglial cells, KG-1-C cells, phagocytose mycobacteria, especially Mycobacterium leprae, were studied. The ability of glial cells to phagocytose M. leprae was inhibited by azide, dinitrophenol (inhibitors of oxidative phosphorylation), and iodoacetamide but not fluoride (both are inhibitors of glycolysis). Thus, the energy metabolism dependency is somewhat different from that of peritoneal macrophages and polymorphonuclear leukocytes, the phagocytic capacities of which are mainly dependent on glycolysis. Phagocytosis of M. leprae by KG-1-C cells was markedly suppressed by a microfilament inhibitor (cytochalasin B) but not microtubule inhibitors (colchicine and vinblastine), as with macrophages. The phagocytosis of M. leprae by KG-1-C cells was dependent on the lipid and somewhat on the sugar ligands of the organism. Moreover, the phagocytosis of a given mycobacterium by KG-1-C cells correlated well with its hydrophobicity, thus revealing the importance of some lipid moieties on the surface of bacteria in the establishment of rigid binding interaction of bacteria with KG-1-C cells, before the onset of engulfment. Electric charge of a given microorganism did not correlate with its phagocytosis by KG-1-C cells.

Differentiation of pancreatic acinar carcinoma cells cultured on rat testicular seminiferous tubular basement membranes.

The use of rat testicular seminiferous tubular basement membrane (STBM) segments as a model substratum for the in vitro maintenance of tumor cells dissociated from a transplantable pancreatic acinar rat carcinoma (J. K. Reddy and M. S. Rao, Science (Wash. DC), 198: 78-80, 1977) is described. Ultrastructurally pure, hollow tubular segments of STBM were prepared by mechanical disaggregation, DNase digestion, and deoxycholate treatment. Dissociated pancreatic acinar carcinoma cells adhered readily to STBM segments within 1 to 6 hr, and these STBM-tumor cell aggregates were maintained for up to 7 days in serum-free chemically defined medium supplemented with hydrocortisone, insulin, vitamin C, and soybean trypsin inhibitor. The tumor cells formed acinar-like clusters and displayed intercellular junctions and polarization of secretory granules toward the center of these clusters. By 4 days, virtually all cells of this acinar carcinoma maintained on STBM in supplemented chemically defined medium contained numerous secretory granules. Cell replication, as determined by [3H]thymidine autoradiography, ceased within 18 hr of attachment of neoplastic cells to STBM; however, all cells incorporated [3H]leucine as evidenced by light and electron microscopic autoradiography. In addition, two-dimensional analysis and fluorography of newly synthesized secretory proteins discharged by these cells in response to carbamylcholine revealed the presence of Mr 24,000 protein and 19 other secretory proteins characteristic of this tumor (L. J. Hansen, M. K. Reddy, and J. K. Reddy, Proc. Natl. Acad. Sci. USA, 80: 4379-4383, 1983). The culture system utilizing STBM and supplemented chemically defined medium should allow investigation of the effects of a variety of factors on morphogenesis, cytodifferentiation, and gene expression in pancreatic acinar tumors.