Translator Disclaimer
1 February 2011 50 Years Later: Remembering the Paper
Author Affiliations +

Sometimes a moment in your life is so important you remember it in startling detail—where you were, who was there, what happened. As a first-year medical student in my first months of research at Stanford, I was walking down the hall of the basement radiation biology labs at Stanford when Henry Kaplan, my mentor and benefactor, stepped out of his lab and motioned me over. In his right hand, for some of you memorable in itself, he held the new issue of Radiation Research. He pointed to the now famous paper (1) and said “You should read this; it will be important.” I spotted the bumps on the spleen and wondered if I would have been astute enough to follow it up rather than trashing the finding as some artifact or infection. Later, when I read the paper, I was struck at how precise the quantitative data on numbers of cells to make a day 10 spleen colony was from an in vivo assay and how precise the radiation sensitivity tests could be. Real in vivo biology could be quantitative. But the major finding came in just a few sentences—each colony had at least four blood cell types (monocytic, granulocytic, erythroid and megakaryocytic), and they proposed that each colony was derived from a single clonal progenitor. They mentioned that the spleen colony-forming cell was probably from an undifferentiated cell.

The term stem cells was not mentioned, but then we had no important definition of such a cell at that time. But the idea of a multilineage clonal progenitor was exciting, and little did I know then how their elegant subsequent papers would establish the concept and set most of the rules. The demonstration that day 10 CFU-s cells were clonal came from one of the most innovative experiments I have read in my lifetime in science—irradiate the donor cells and check for unique chromosomal aberrations in the survivors, and if all dividing cells in a colony had the same random and unique marker, which they did, the colonies were clonal (2). Then the demonstration that sometimes day 10 colonies had also produced many day 10 CFU-s clonal progenitors led to the idea of at least short-term self-renewal (3). Finally, the use of this technique to follow cells a little longer and to show lymphocytes could be part of the clone revealed that the bone marrow contained infrequent cells capable of multilineage myeloerythroid and sometimes lymphoid maturation, and at least some of these could self-renew for the time intervals studied (4). By then the term stem cells was being used, in fact pluripotent hematopoietic stem cells (a term changed to recognize the potency of ES cells). I knew from then that any cell isolated that could do less than self-renew as well as give rise in its clonal progeny to all known blood cells types would not make the grade as a stem cell.

When later I came back to the identification and prospective isolation of HSC following the lead of pursuing T- and B-lymphocyte progenitors (56789), we had established clonal assays for all progenitors. We started with a thymic colony assay that also measured clonogenic marrow cells (101112), a clonal assay for B-lymphocyte progenitors (13) on clonal stromal cells taken from Whitlock-Witte cultures (14), and myeloerythroid colony-forming cells at day 12–14 in the spleen; we followed the Iscove et al. correction of the time of separate progenitors to form day 8 or 10 or 12–14 splenic colonies (15). [We later showed that oligolineage progenitors gave rise to day 8 CFU-s, and mainly multipotent progenitors and HSC to day 12 CFU-s (16)]. And, like others, we found that long-term multilineage engraftment of all blood cell types in lethally irradiated hosts was another assay (13), as was retransplantation from purified cells of a particular phenotype. With the availability of the hybridoma techniques to get a constant reagent for a constant cell surface epitope (17), and the fluorescence-activated cell sorter (18), we could isolate marked marrow cells for simultaneous assay in all of the tests described above. We reported high enrichment of HSC (13), then even higher (19, 20), and over the next 20 years many HSC subsets and nearly all of the downstream progenitors in mice (2122232425) and in humans (262728). Much to our delight, both mouse and human HSC markers were so unique we could isolate T-cell-free HSC for allogeneic transplantation without GvH (2930) and cancer-free HSC from patients with widespread breast cancers or lymphomas, so that HSC rescue after myeloablative chemotherapy could be done without re-introducing cancer cells to the patients [(31, 32), Mueller et al., Long-term followup of patients with metastatic breast cancer treated with high-dose chemotherapy and transplantation of highly purified hematopoietic stem cells, manuscript in preparation]. So it was clear to me that the field initiated by Till and McCulloch in the 1960s could be the basis for many clinical therapies, including regenerative medicine for a number of tissues when the stem cell assays and isolation method was extended to these other tissues (333435).

That is the field established by a biophysicist and hematologist-oncologist wishing to develop an assay of normal tissue radiosensitivity to compare with cancer radiosensitivity by injecting bone marrow cells into mice and seeing bumps. They were wise enough to recognize far more than pathology to explain the bumps and had the vision and the experimental innovation to show that HSC exist, and they and their school of stem cell biology and medicine in Toronto have provided the world with the most remarkable field.



J. E. Till and E. A. McCulloch . A direct measurement of the radiation sensitivity of normal mouse bone marrow cells. Radiat. Res 14:213–222. 1961.  Google Scholar


A. J. Becker, E. A. McCulloch, and J. E. Till . Cytological demonstration of the clonal nature of spleen colonies derived from transplanted mouse marrow cells. Nature 197:452–454. 1963.  Google Scholar


L. Siminovitch, E. A. McCulloch, and J. E. Till . The distribution of colony-forming cells among spleen colonies. J. Cell Physiol 62:327–336. 1963.  Google Scholar


A. M. Wu, J. E. Till, L. Siminovitch, and E. A. McCulloch . A cytological study of the capacity for differentiation of normal hemopoietic colony-forming cells. J. Cell Physiol 69:177–184. 1967.  Google Scholar


G. A. Gutman and I. L. Weissman . Lymphoid tissue architecture. Experimental analysis of the origin and distribution of T-cells and B-cells. Immunology 23:465–479. 1972.  Google Scholar


R. L. Coffman and I. L. Weissman . Immunoglobulin gene rearrangement during pre-B cell differentiation. J. Mol. Cell. Immunol 1:31–41. 1983.  Google Scholar


I. Weissman, V. Papaioannou, and R. Gardner . Fetal hematopoietic origins of the adult hemato lymphoid system. In Differentiation of Normal and Neoplastic Hematopoietic Cells (Cold Spring Harbor Conferences on Cell Proliferation 5). B. Clarkson, P. A. Marks, and J. E. Till . Eds. pp. 33–47. Cold Spring Harbor Laboratory Press. Cold Spring Harbor, NY. 1978.  Google Scholar


R. Scollay, M. Kochen, E. Butcher, and I. Weissman . Lyt markers on thymus cell migrants. Nature 276:79–80. 1978.  Google Scholar


C. G. Fathman, M. Small, L. A. Herzenberg, and I. L. Weissman . Thymus cell maturation. II. Differentiation of three “mature” subclasses in vivo. Cell Immunol 15:109–128. 1975.  Google Scholar


F. Lepault and I. L. Weissman . An in vivo assay for thymus-homing bone marrow cells. Nature 293:151–154. 1981.  Google Scholar


F. Lepault, R. L. Coffman, and I. L. Weissman . Characteristics of thymus-homing bone marrow cells. J. Immunol 131:64–69. 1983.  Google Scholar


S. Ezine, I. L. Weissman, and R. V. Rouse . Bone marrow cells give rise to distinct cell clones within the thymus. Nature 309:629–631. 1984.  Google Scholar


C. E. Muller-Sieburg, C. A. Whitlock, and I. L. Weissman . Isolation of two early B lymphocyte progenitors from mouse marrow: a committed pre-pre-B cell and a clonogenic Thy-1-lo hematopoietic stem cell. Cell 44:653–662. 1986.  Google Scholar


C. A. Whitlock, G. F. Tidmarsh, C. Muller-Sieburg, and I. L. Weissman . Bone marrow stromal cell lines with lymphopoietic activity express high levels of a pre-B neoplasia-associated molecule. Cell 48:1009–1021. 1987.  Google Scholar


M. C. Magli, N. N. Iscove, and N. Odartchenko . Transient nature of early haematopoietic spleen colonies. Nature 295:527–529. 1982.  Google Scholar


T. Na Nakorn, D. Traver, I. L. Weissman, and K. Akashi . Myeloerythroid-restricted progenitors are sufficient to confer radioprotection and provide the majority of day 8 CFU-S. J. Clin. Invest 109:1579–1585. 2002.  Google Scholar


G. Kohler and C. Milstein . Continuous cultures of fused cells secreting antibody of predefined specificity. Nature 256:495–497. 1975.  Google Scholar


H. R. Hulett, W. A. Bonner, J. Barrett, and L. A. Herzenberg . Cell sorting: automated separation of mammalian cells as a function of intracellular fluorescence. Science 166:747–749. 1969.  Google Scholar


G. J. Spangrude, S. Heimfeld, and I. L. Weissman . Purification and characterization of mouse hematopoietic stem cells. Science 241:58–62. 1988.  Google Scholar


K. Ikuta and I. L. Weissman . Evidence that hematopoietic stem cells express mouse c-kit but do not depend on steel factor for their generation. Proc. Natl. Acad. Sci. USA 89:1502–1506. 1992.  Google Scholar


S. J. Morrison and I. L. Weissman . The long-term repopulating subset of hematopoietic stem cells is deterministic and isolatable by phenotype. Immunity 1:661–673. 1994.  Google Scholar


M. Kondo, I. L. Weissman, and K. Akashi . Identification of clonogenic common lymphoid progenitors in mouse bone marrow. Cell 91:661–672. 1997.  Google Scholar


K. Akashi, D. Traver, T. Miyamoto, and I. L. Weissman . A clonogenic common myeloid progenitor that gives rise to all myeloid lineages. Nature 404:93–97. 2000.  Google Scholar


K. Akashi and I. L. Weissman . The c-kit+ maturation pathway in mouse thymic T cell development: lineages and selection. Immunity 5:147–161. 1996.  Google Scholar


D. Traver, K. Akashi, M. Manz, M. Merad, T. Miyamoto, E. G. Engleman, and I. L. Weissman . Development of CD8alpha-positive dendritic cells from a common myeloid progenitor. Science 290:2152–2154. 2000.  Google Scholar


C. M. Baum, I. L. Weissman, A. S. Tsukamoto, A. M. Buckle, and B. Peault . Isolation of a candidate human hematopoietic stem-cell population. Proc. Natl. Acad. Sci. USA 89:2804–2808. 1992.  Google Scholar


M. G. Manz, T. Miyamoto, K. Akashi, and I. L. Weissman . Prospective isolation of human clonogenic common myeloid progenitors. Proc. Natl. Acad. Sci. USA 99:11872–11877. 2002.  Google Scholar


R. Majeti, C. Y. Park, and I. L. Weissman . Identification of a hierarchy of multipotent hematopoietic progenitors in human cord blood. Cell Stem Cell 1:635–645. 2007.  Google Scholar


J. A. Shizuru, L. Jerabek, C. T. Edwards, and I. L. Weissman . Transplantation of purified hematopoietic stem cells: requirements for overcoming the barriers of allogeneic engraftment. Biol. Blood Marrow Transplant 2:3–14. 1996.  Google Scholar


K. L. Gandy and I. L. Weissman . Tolerance of allogeneic heart grafts in mice simultaneously reconstituted with purified allogeneic hematopoietic stem cells. Transplantation 65:295–304. 1998.  Google Scholar


R. S. Negrin, K. Atkinson, T. Leemhuis, E. Hanania, C. Juttner, K. Tierney, W. W. Hu, L. J. Johnston, J. A. Shizuru, and J. Klein . Transplantation of highly purified CD34+Thy-1+ hematopoietic stem cells in patients with metastatic breast cancer. Biol. Blood Marrow Transplant 6:262–271. 2000.  Google Scholar


J. M. Vose, P. J. Bierman, J. C. Lynch, K. Atkinson, C. Juttner, C. E. Hanania, G. Bociek, and J. O. Armitage . Transplantation of highly purified CD34+Thy-1+ hematopoietic stem cells in patients with recurrent indolent non-Hodgkin's lymphoma. Biol. Blood Marrow Transplant 7:680–687. 2001.  Google Scholar


N. Uchida, D. W. Buck, D. He, M. J. Reitsma, M. Masek, T. V. Phan, A. S. Tsukamoto, F. H. Gage, and I. L. Weissman . Direct isolation of human central nervous system stem cells. Proc. Natl. Acad. Sci. USA 97:14720–14725. 2000.  Google Scholar


R. I. Sherwood, J. L. Christensen, I. M. Conboy, M. J. Conboy, T. A. Rando, I. L. Weissman, and A. J. Wagers . Isolation of adult mouse myogenic progenitors; functional heterogeneity of cells within and engrafting skeletal muscle. Cell 119:543–554. 2004.  Google Scholar


C. K. Chan, C. C. Chen, C. A. Luppen, J. B. Kim, A. T. Deboer, K. Wei, J. A. Helms, C. J. Kuo, D. L. Kraft, and I. L. Weissman . Endochondral ossification is required for haematopoietic stem-cell niche formation. Nature 457:490–494. 2009.  Google Scholar
Irving L. Weissman "50 Years Later: Remembering the Paper," Radiation Research 175(2), 143-144, (1 February 2011).
Published: 1 February 2011

Back to Top