B memory cells in the thymus: part of the pool of potentially circulating memory cells.

Immunization of mice with sheep red blood cells (SRBC) or Escherichia coli lipopolysaccharide (LPS) induces the appearance of B memory cells in the thymus. In this paper the origin of these B memory cells was investigated. Therefore, mice primed with either SRBC or LPS 6 months previously and nonprimed mice were joined for parabiosis. Four weeks later the parabiotic mice were separated from each other. Another 3 weeks later thymus cells from the primed and nonprimed mice were transferred separately into lethally irradiated mice in order to determine the adoptive PFC response. It was found that the 4-week period of parabiosis could account for the appearance of a distinct population of B memory cells in the thymus of the nonprimed mice. This result suggest that the B memory cells which appear in the thymus belong to the pool of potentially circulating memory cells.