Identification of thymocyte progenitors in hemopoietic tissues of the rat. II. Enrichment of functional prothymocytes on the fluorescence-activated cell sorter.

Abstract

A quantitative thymocyte regeneration assay was used to monitor the isolation of functional prothymocytes from rat bone marrow in the FACS [fluorescence-activated cell sorter]. Two prothymocyte subpopulations were tentatively identified on the basis of their relative resistance to dexamethasone. Both populations were comprised of undifferentiated, medium-size cells that displayed large amounts of Thy[thymus]-1 antigen. Simultaneous sorting of bone marrow cells according to relative low angle light scatter (size) and relative fluorescence intensity for Thy-1 resulted in enrichments of 112- and 260-fold, respectively, in prothymocyte activity in untreated and dexamethasone-treated bone marrow. These prothymocyte-enriched cell fractions contained .apprx. 75% of total functional prothymocyte activity in bone marrow, and represented 1.1 and 0.35% of total untreated and dexamethasone-treated bone marrow cells. Using these enriched cell fractions, significant thymocyte regeneration is possible with as few as 2 .times. 104 and 1 .times. 104 bone marrow cells, respectively. The possible relationship of these functional prothymocyte subpopulations with CFU-S [spleen colony forming unit] and with TdT[terminal deoxynucleotidyl transferase]-positive cells is discussed.