Investigation of the Blastogenic and Cytotoxic Capabilities of Human Bone Marrow: Differences Between Aspirate and Rib Marrow

Abstract

The use of marrow aspirates in bone marrow transplantation, clinical evaluation, and experimental studies has prompted the present study of the functional characteristics of mononuclear cells from aspirated (iliac crest) and curettaged (rib) marrow. In this manner, the relative contribution of peripheral blood contamination of aspirated bone marrow cells in investigating and understanding marrow function can be assessed. Human bone marrow specimens were collected using 3-5 ml aspirates from the iliac crest in 17 individuals and using curettage of ribs obtained from 13 individuals undergoing thoracotomy. The marrow samples were separated over discontinuous Ficoll-Hypaque gradients. Mononuclear cells from aspirated marrow had a high background stimulation and therefore no significant response to lectins (Con-A, E-PHA, PWM) or responsiveness in mixed lymphocyte culture (MLC), whereas mononuclear cells from rib marrow had a low unstimulated background activity and could be stimulated by E-PHA and allogeneic cells in MLC. Bone marrow cells obtained from aspirates and ribs were also studied as to their ability to mediate in vitro cellular cytotoxicity. Antibody-dependent cellular cytotoxicity (ADCC) and lectin-induced cytotoxicity (LICC) were observed using marrow mononuclear cells from both sources when red cells were employed as targets. In contrast, when cell line target cells were employed, rib mononuclear cells were not observed to mediate lysis, whereas mononuclear cells from aspirates did lyse these targets. The cytotoxicity observed with aspirates was therefore most likely due to peripheral blood contamination. In cell-mediated lympholysis (CML), rib mononuclear cells were not stimulated to kill allogeneic lymphocytes, while aspirated cells lysed allogeneic lymphocytes about 50% as well as did peripheral blood mononuclear cells (PBC), again, a reflection of peripheral blood contamination. We therefore conclude that pure bone marrow from humans, as assessed by studies using curettaged marrow from ribs, contains mononuclear cells capable of responding blastogenically to E-PHA and to cell surface alloantigens, as well as cells able to mediate LICC and ADCC against RBC, but does not include a population of cells able to lyse cell line targets in ADCC, spontaneous cell-mediated cytotoxicity (SCMC), or CML. These results indicate that the clinical evaluation, experimental study, and therapeutic use of bone marrow must be undertaken with the understanding that significant contamination with peripheral blood can occur when aspirates are used and that curettaged or biopsy material be used when true bone marrow is desired or needed.