Precursor Cells in Density Fractions of Lymph Node Cells: Relation to Antibody-Producing Cells

Abstract

Abstract Spleen cells of mice were transferred intravenously into x-irradiated syngeneic recipients which were also injected with sheep red blood cells (SRBC). The dose of irradiation was sufficient to prevent active immunization by the SRBC injected. At intervals thereafter, spleens of recipients were teased and the cells plated in agar against SRBC, to determine relative numbers of precursor cells for this immunologic response which had been transferred. In normal mouse spleen cells fractionated by bovine plasma albumin (BPA) density gradient centrifugation, cells pooled from the higher or the lower density range of fractions yielded equal numbers of plaque-forming cells (PFC) in the recipients' spleens 6 to 8 days later. The same was found in cells obtained from spleens 30 days after primary injection of SRBC. In cells obtained 5 days after secondary injection of SRBC, however, the low density cells contained more precursor cells per million than cells in the high density fractions. In other portions of such spleen cell suspensions, which had been incubated for the production of anti-SRBC rosettes and then fractionated, the high density fraction again contained fewer precursor cells per million than the low density fraction. In this case, the high density fractions also contained the rosette-forming cells (RFC) because these were now included in rosettes. The latter, the high density, rosette-rich, fraction of the rosette preparation produced no more precursor cells than the similar fraction of the original suspension, indicating that the cells currently producing antibody were not a major source of precursor cells.