Depletion of T lymphocytes from human bone marrow by the use of counterflow elutriation centrifugation

Abstract
Normal donor bone marrow buffy coat (BMBC) cells were fractionated into three subsets by counterflow elutriation centrifugation. Fraction 1 (Fr-1) was lymphocyteenriched, fraction 2 (Fr-2) was a mixture of lymphocytes and myelomonocytic cells, and fraction 3 (Fr-3) was enriched for myelomonocytic cells. The extent of T cell depletion was determined by limiting dilution analysis of the growth of T cells. The cells in each group were stimulated with phytohemagglutinin and cultured in the presence of interleukin-2. These conditions allowed clonogenic growth of one of three T cells purified from peripheral blood. After a 3-week culture period, replicate wells were scored for growth and precursor frequency was determined. The frequency of T cells in BMBC was 1/22 (n = 4), 1/16 in FR-1 (n = 4), and 1/246 in Fr-2 (n = 2), and in Fr-3 it ranged from 1/3,000 to 1/10,000 (n = 4). For comparison, depletion of T cells from bone marrow by cytofluorographic sorting with OKT-11 and twice E-rosetting yielded 98.1% and 97.4% removal of T cells, respectively. Thus, the clonogenic assay assured that more than 99.3% of the original T cells were depleted by elutriation; however, hematopoietic progenitor assay (CFU-GM, CFU-GEMM, and BFU-E) showed no enrichment in any particular fraction, implying that the progenitors measured in this assay are of diverse sizes. Elutriation represents a useful method for depletion of T cells from human bone marrow. Limiting dilution assay of T cell growth is a sensitive measure to monitor T cell depletion.

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