PANCREATIC HORMONE EXPRESSION IN THE MURINE THYMUS - LOCALIZATION IN DENDRITIC CELLS AND MACROPHAGES

The expression of preproinsulin (ppIns), proglucagon, prosomatostatin, and propancreatic polypeptide was investigated in thymic extracts, th ymic cells, and thymic cell lines from C57BL/6 mice by PT-POP. The exp ression of pancreatic hormones was similar in thymic extracts taken fr om neonatal and 2-, 4-, and 8-week-old animals, but was decreased in 2 0-week-old animals. Pancreatic hormone expression was not observed in mouse liver, salivary gland, or spleen. Analysis of thymic cell popula tions revealed a 10- to 20-fold enrichment in expression of all hormon es in low buoyant density cells. No expression was detected in high bu oyant density cells (predominantly thymocytes) or in thymic epithelial cell lines, primary cultures of epithelial cells, or peripheral macro phages. In addition, immunoreactive insulin, measured by specific RIA, was detectable in the low buoyant density population, but not in high buoyant density cells. The enriched cell population was depleted of c ontaminating lymphocytes and sorted based on reactivity to the cell, s urface markers F4/80 (macrophage) or N418 (dendritic cells). Cells gat ed for N418 demonstrated expression for ppIns, but not the other pancr eatic hormones. Conversely, expression for proglucagon, prosomatostati n, and pro-pancreatic polypeptide, but not ppIns, was detected in F4/8 0-gated cells. Our data indicate that pancreatic endocrine hormones ar e differentially expressed by dendritic cells and macrophages in a nor mal mice.