Accumulation of bromodeoxyuridine‐labeled cells in central and peripheral lymphoid organs: minimal estimates of prodution and turnover rates of mature lymphocytes

Abstract

Daily lymphocyte production in both central and peripheral lymphoid organs was evaluated by associating in vivo incorporation of bromodeoxyuridine (BrdUrd) with cell surface labeling and multi-parameter flow analysis. At least 10% of mature T and B lymphocytes are generated every 24 h. The kinetic behavior of these cell populations differs, however, in that mature B cells are generated predominantly in the precursor compartments of the bone marrow, while most mature T cell generation occurs at the periphery. Therefore, peripheral expansion is the major mechanism of mature T cell production in the adult mouse. By following the accumulation of BrdUrd-labeled cells in peripheral lymphoid organs we found that the progeny of the daily lymphocyte production was sufficient to renew 30%-40% of all peripheral T and B cells every 48 h, demonstrating a high turnover rate of mature lymphocytes. We also examined the conditions of BrdUrd labeling of cycling cells in vivo. We found that while greater than 90% of bone marrow and thymus cells in S phase were labeled with a single injection of BrdUrd, in peripheral lymphoid compartments 70% of T and B cells in S failed to incorporate BrdUrd. Particular schedules of BrdUrd administration were required to overcome the low labeling efficiency of mature cells in vivo. Prolonged BrdUrd administration, however, had toxic effects on resident cells. The low labeling efficiency of BrdUrd incorporation by mature cells, as well as its potential toxicity during prolonged administration, may explain controversial results obtained by the different strategies used to study lymphocyte population dynamics.

Relatively Normal Human Lymphopoiesis but Rapid Turnover of Newly Formed B Cells in Transplanted Nonobese Diabetic/SCID Mice

“…This accords with the immaturity of human B cells with respect to CD24 density, presence of CD38, and display of CD10. Such newly formed lymphocytes normally represent a small fraction of rodent spleens, and a majority of the B cells are long-lived (21,23,32,71). There is little information about the normal fate and life span of CD5 ϩ B cells in humans and most of the lymphocytes in chimeric mice expressed this marker.…”

“…This dose was based on previous studies (21). The water bottle containing the BrdU solution was protected from light and changed every 2-3 days throughout the time course of the experiment.…”

Measurement in vivo of proliferation rates of slow turnover cells by 2 H 2 O labeling of the deoxyribose moiety of DNA

“…This approach has several important limitations, however. In particular, these reagents cannot be used safely in humans because of toxicities (4,5), are difficult to interpret during the die-away or de-labeling phase for assessment of cell death (6) and are particularly problematic for measurement of kinetics of cell populations that turn over slowly in vivo.…”

“…Toxicities of 3 HdT and BrdUrd include mutagenicity, impairment of cell division (e.g., myelosuppressive effects), and killing of susceptible cells (4,5). Biochemical complications, such as reutilization of labeled pyrimidine nucleosides released from dying cells (7,8) and unpredictable uptake efficiency of administered label by dividing cells (5)(6)(7)(8), constrain measurement of slow turnover (longlived) tissues.…”

“…Biochemical complications, such as reutilization of labeled pyrimidine nucleosides released from dying cells (7,8) and unpredictable uptake efficiency of administered label by dividing cells (5)(6)(7)(8), constrain measurement of slow turnover (longlived) tissues.…”