Murine recombinant interleukin-3 induces recovery of T and B cells in irradiated mice

Injection of murine recombinant interleukin-3 (IL-3) into (C57BL/10 x DBA/2) F1 mice, sublethally irradiated with 300 cGy and killed 14 days later, induced in the thymus recovery of the cell number and mitotic responsiveness to concanavalin A (Con A), as well as an increase in number of double- negative CD4^-CD8^-, double-positive CD4⁺CD8⁺, and single-positive CD4⁺CD8^- and CD4^-CD8⁺ cells. Also in the spleen, the cell count and mitotic responsiveness to Con A and lipopolysaccharide were increased to normal levels by IL-3 treatment. If the assays were performed 21 or 28 days after irradiation, IL-3 treatment was able to restore thymus and spleen cell counts as well as T- and B-cell mitotic responsiveness, even when mice were exposed to 400 or 500 cGy, respectively. These results altogether indicate that IL-3 induces differentiation and growth of thymocytes and recovery of T- and B-cell functions in mice exposed to sublethal irradiation.