Search

In mice a macromolecular insoluble cold globulin (MICG) is present on the surface of resting and stimulated peripheral T lymphocytes, thymocytes, fetal prothymocytes and hemopoietic stem cells forming spleen colonies, colony-forming unit-spleen (CFU-S). Here we demonstrate that removal of MICG positive cells from bone marrow by treatment with antibody and complement does not affect the number of erythroid, burst-forming unit-erythroid (BFU-E) and granulocyte-macrophage, colony-forming unit-granulocyte macrophage (CFU-GM) progenitors developing in vitro. Thus, commitment of stem cells to lineage specific differentiation is associated with the loss of the MICG marker. Furthermore, the removal of MICG positive T lymphocytes from bone marrow does not affect the growth of BFU-E or CFU-GM.

Circulating CFU-GM, BFU-E and CFU-MIX were assayed in 21 infants aged between 1 day and 44 weeks. Compared to 15 adults, progenitor cells of all types were increased until 10 weeks following birth and approached the respective ranges of adults thereafter. The mean increases of progenitor cells in infants aged between 1 day and 10 weeks were 26-fold for CFU-GM, 7-fold for BFU-E and 5-fold for CFU-MIX. Our results demonstrate that not only committed progenitor cells (CFU-GM, BFU-E), but also early progenitor cells with the capacity for self-renewal (CFU-MIX), are increased in early infancy. These data further support the hypothesis that high levels of blood progenitor cells in very early stages of life reflect the colonization process of developing bone marrow by circulating progenitor cells and demonstrate the terminal phase of this process during the first 10 weeks after birth.

Differential screening of a CML-derived cDNA library was used to isolate a cDNA clone representing an abundant mRNA in leukocytes of chronic phase, chronic myelogenous leukemia (CML) patients. This myeloid-related sequence (mrs) comprises approximately 2% of the chronic phase, CML mRNA. Hybridization of the radiolabeled cDNA to the cellular RNAs of intact, morphologically distinguishable, primary hematopoietic cells indicates that the primary cells producing mrs RNA are eosinophils (Eo), basophils (Baso), promyelocytes (Pro) and myelocytes (Mye). In the neutrophilic series, the abundance of mrs RNA decreases as the cells mature. The mrs RNA potentially encodes a 93 amino acid protein that has not been previously described. It has been localized to chromosome 8, region 8q21.1-23.

Bone marrow cells from a patient with pancytopenia and a lymphoproliferative disorder of large granular lymphocytes (LGL) were cultured and tested for their hemopoietic colony-forming potential. Neither erythroid nor granulocyte-macrophage colony formation could be obtained from unfractionated, or LGL-depleted bone marrow cell preparations. However, a spontaneous growth of lymphoid colonies was observed after culturing LGL-depleted (T3-) bone marrow cell suspensions for 25 days. Pooled colonies expanded with recombinant interleukin-2 yielded a population composed predominantly of mature T cells (T3+, Leu 6-). These findings suggest that some (T3-) T cell precursors may mature in the bone marrow and that, in our patient, LGL may have exerted a suppressor effect on this maturational process.

It has been found possible to test ferritin concentrations in the reticulum and hemopoietic cells from human bone marrow by an immunoradiometric assay. Ferritin concentration in healthy test persons amounts to 0.92 +/- 0.38 ng/microgram protein in the reticulum and 0.084 +/- 0.031 ng/microgram protein in hemopoietic cells. In healthy test persons about 90% of the ferritin is localized in the reticulum and about 10% in the hemopoietic cells. The ferritin concentration in the reticulum is decreased in patients having iron deficiency anemia. In these patients only 50-70% of the bone marrow ferritin is localized in the reticulum. Bone marrow ferritin was characterized by a combination of anion-exchange chromatography using Sephadex A-50 and an immunoradiometric assay. Marrow ferritin from healthy persons is eluted at chloride concentrations between 200 and 300 mM. The anion-exchange chromatographic properties of ferritin in the reticulum and hemopoietic cells are identical.