title: Studies on thymocyte subpopulations in guinea pigs. Differences in cell volume and proliferative ability in vitro of two populations separated by density gradient centrifugation with Percoll.
abstract: Thymus cells from guinea pigs were separated according to buoyant density by centrifugation with PVP-coated colloidal silica particles (Percoll). By creating an S-shaped density gradient, two populations (referred to as peak-I and peak-II cells) were obtained which differed in size as well as ability to spontaneous proliferation in vitro. Peak I contained low density cells of large size and was highly enriched with DNA-synthesizing cells. These continued to proliferate in culture for at least 30 h as demonstrated by mitotic studies in the intervals 0-10 and 20-30 h. In order to grow in vitro, however, the cycling cells of peak I depended on the medium (RPMI 1640) being supplemented with L-alanine. The high density cells of peak II constituted 70% of the thymocytes and had a small and uniform volume. This population was depleted of proliferating cells. The simple and rapid separation of these two major populations is considered a useful first step for the further characterization of thymocyte subpopulations. We suggest that peak I primarily includes proliferating precursor cells from the cortex as well as mature, immunocompetent cells. Peak II consists largely of small cortical cells.
mesh_terms: D000818:Animals; D002452:Cell Count; D002455:Cell Division; D002469:Cell Separation / Q000379:methods; D002499:Centrifugation, Density Gradient / Q000379:methods; D003102:Colloids; D006168:Guinea Pigs; D008297:Male; D011205:Povidone; D012822:Silicon Dioxide; D013601:T-Lymphocytes / Q000145:classification* / Q000166:cytology
chemical_list: D003102:Colloids; C016039:Percoll; D012822:Silicon Dioxide; D011205:Povidone