The majority of "natural" immunoglobulin-secreting cells are short-lived and the progeny of cycling lymphocytes.

Treatment of mice with hydroxyurea to selectively kill all cycling cells has been used to study population dynamics and life expectancy of "natural" immunoglobulin-secreting cells in the bone marrow and spleen of nonimmunized animals. The results show that 50 to 90% of those cells are eliminated 2 to 3 days after one cycle of hydroxyurea administration, demonstrating their recent origin from cycling precursors. Using a protocol of long-term hydroxyurea treatment which abrogates cell production from the cycling precursors compartments, it was shown that "natural" immunoglobulin-secreting cells have a very short half renewal time, in the range of 15-60 h.