The differentiation factor in the bone marrow and blood serum of healthy subjects and in acute leukemia

The factor of differentiation--i.e. systemic morphogen of connective tissue (SMCT)--have been discovered in bone marrow and blood serum of healthy humans. SMCT calls forth the differentiation of mesodermal cell types in early embryonic amphibian cells. These cell types are the following: notochords, muscles, mesothelium, blood cells, mesenchyme. Under the influence of the punctates of bone marrow the frequency of muscle and blood cell appearance is not constant, which might be the consequence of the individual variability of SMCT. Under the influence of bone marrow and blood serum in patients with acute lymphoblastic, monoblastic and myelomonoblastic leukemia the embryonic cells differentiate only into atypical epidermis, which proves the absence of the SMCT activity in the sources used. In some cases under the influence of bone marrow from patients having the same disease the early embryonic cells differentiate into mesodermal cell types, which normally appear under the low concentration of SMCT. This was observed however only in those cases when bone marrow or blood serum have been taken from patients in the state of remission. In patients with remission the correlation is observed between the activity of factor of differentiation in bone marrow and that of blood serum.     

Interactions between lymphocytes and hematopoietic progenitor cells in normal and leukemic human bone marrow (phase contrast observations)

Single cell observations of normal and of leukemic human bone marrow cells demonstrated cell-cell interactions of lymphocytes with hematopoietic progenitor cells. In all cases lymphocytes and target cells were from the same individual. Lymphocyte-target cell interactions occurred more frequently with normal committed progenitor cells and leukemic blast cells from acute myeloid leukemia than with precursor cells of the proliferative cell pool, including myeloblasts, promonocytes, erythroblasts and megakaryocytes. Both induction of mitosis and degeneration of the progenitor cells occurred after cell-cell interaction with almost the same frequency. Acute myeloid leukemic blast cells degenerated after contact with lymphocytes with the same frequency as normal progenitor cells (i. e. in 16% of cell contacts), but especially during mitosis. In contrast, normal and regenerating bone marrow progenitor cells from myeloproliferative diseases demonstrated no degeneration after cell-cell interaction with lymphocytes during mitosis. Otherwise the induction of mitoses by lymphocyte-target cell interactions was more frequently observed in normal progenitor cells than in leukemic blasts.     

Association between leukemic erythroid progenitors and bone marrow macrophages

Previous ultrastructural investigations have shown that the erythroblastic island is composed of erythroblasts at different stages of maturation which are intimately associated with a central macrophage. However, it is still unclear at which stage of erythroid differentiation this interaction occurs, mainly because of the lack of purified populations of normal erythroid progenitors [erythroid colony-forming units (CFU-E) and erythroid burst-forming units (BFU-E)] and early precursor cells (proerythroblasts) and because of our limited knowledge of their ultrastructural characteristics. In the present work we analyzed the ultrastructure of CFU-E enriched from normal human bone marrow by avidin-biotin immune rosetting and leukemic blasts of erythroid origin from two patients. Normal and leukemic CFU-Es were defined as glycophorin A (GPA)-negative blasts, devoid of rhopheocytosis, containing some ferritin molecules, either free in the cytoplasm or associated with theta-granules (theta-Gr) in the Golgi zone. Peroxidase activity was detected in the endoplasmic reticulum of these blasts. A preproerythroblast stage was identified, which corresponded to an intermediate phenotype with few GPA sites and rhopheocytosis. In contrast to hemoglobin synthesis, which was absolutely dependent on the presence of erythropoietin (Epo) during culture for 24 hours, ferritin molecules accumulated in the absence of Epo. Interestingly, leukemic CFU-E-like blasts were always in contact with bone marrow macrophages and adhesion between these cell types resisted mechanical dissociation. This result suggests that erythroid progenitors may be part of the erythroblastic island. The mechanisms involved in erythroblast-macrophage binding are still unknown, but the expression by macrophages and erythroid progenitors of receptors for fibronectin and thrombospondin (TSP), as well as their respective ligands in the case of macrophages, suggests that these molecules could be involved in the formation of the erythroblastic island.     

Effect of a sulfhydryl inhibitor on in vitro bone marrow colonies (CFU-c)

A dose-related increase in the number of in vitro colony-forming units. CFU-c, was observed in mouse bone marrow cell suspensions following the administration of the sulfhydryl inhibitor, sodium iodoacetate. No effect on CFU-s was observed at the dosages and the periods selected for examination. Direct exposure of marrow cells in vitro to various concentrations of iodoacetate did not influence colony formation.     

Immunoadsorption for removal of anti-A and anti-B blood group antibodies in ABO-incompatible bone marrow transplantation

About 10-15 percent of all patients undergoing allogeneic bone marrow transplantation have a major ABO-incompatibility with their donors. The risk of acute hemolytic reactions due to the infusion of an incompatible donor marrow into the recipient can basically be prevented by recipient antibody depletion or by donor marrow red cell depletion. Nine patients were treated by immunoadsorption using a cartridge with chemically synthesized human blood group A and B antigen as immunoadsorbent for antibody depletion. Within a four-hour-procedure about 2-4 times the patient plasma volume could be processed, thus lowering the anti-A and -B hemagglutinins by 2 to 3 tubes. There was a tendency of better IgG removal when titers initially were high, showing a high antibody clearing capacity. There was no significant correlation between starting titer or amount of plasma volume processed and titer reduction. No decrease in titers were observed in one case. We propose repeated immunoadsorption procedures over 2-3 consecutive days before BMT. The procedure is largely safe and without serious side effects. A major advantage is the avoidance of nonautologous human blood products compared to the conventional plasma exchange. All 8 patients surviving long enough had prompt and stable engraftment of all three cell lines post BMT. No late serological complications occurred when patients were regularly monitored and in vivo adsorption was used when titers increased.     

How do normal and leukemic white blood cells egress from the bone marrow? Morphological facts and biochemical riddles

Under normal circumstances only mature granulocytes and monocytes cross the bone marrow sinus wall, a trilaminar structure consisting of endothelial cells, a discontinuous basal membrane and an adventitial cell layer in order to get access to the blood circulation. In leukemia, however, immature white blood cells are able to traverse the barrier and to appear in the blood stream. Very little is known about the regulatory processes which govern the egress of white blood cells in healthy individuals and their malignant counterparts in patients with leukemia. The results of the few studies performed to address this question in animal and human leukemias all agree that the extent to which adventitial cells (fibroblasts) cover the endothelium in bone marrow is drastically reduced. This implies altered interactions between the leukemic and adventitial cells and their extracellular matrix. We propose here a model to explain the egress of normal cells and their leukemic counterparts. It is based upon our own experimental data and the general at present limited knowledge of the subject. It is hoped that this model will stimulate further research into this important aspect of leukemogenesis.