Experiment K-6-23. Effect of spaceflight on levels and function of immune cells

Two different immunology experiments were performed on samples received from rats flown on Cosmos 1887. In the first experiment, rat bone marrow cells were examined in Moscow for their response to colony stimulating factor-M. In the second experiment, rat spleen and bone marrow cells were stained in Moscow with a variety of antibodies directed against cell surface antigenic markers. These cells were preserved and shipped to the United States where they were subjected to analysis on a flow cytometer. The results of the studies indicate that bone marrow cells from flown rats showed a decreased response to colony stimulating factor than did bone marrow cells from control rats. There was a higher percentage of spleen cells from flown rats staining positively for pan-T-cell, suppressor-T-cell and innate interleukin-2 receptor antigens than from control animals. In addition, a higher percentage of cells that appeared to be part of the myelogenous population of bone marrow cells from flown rats stained positively for surface immunoglobulin than did equivalent cells from control rats

A quantitative assay for transformation of bone marrow cells by Abelson murine leukemia virus

A quantitative Abelson murine leukemia virus (A-MuLV) lymphoid cell transformation assay has been developed using a semisolid agarose culture system. Under these conditions lymphoid cell transformation was shown to vary linearly with the dose of A-MuLV used. The susceptibility of bone marrow cells from different strains of mice to A-MuLV-induced transformation can be estimated using the agarose assay. Strains with bone marrow cells of high, medium, and low susceptibility to A-MuLV can be identified. The assay has been used to study the susceptibility of cells from lymphoid organs of fetal and adult mice to A-MuLV. Cell suspensions from fetal liver, adult bone marrow, and adult spleen are susceptible to A-MuLV, while thymocytes are resistant to A-MuLV-induced transformation. Bovine serum albumin gradient fractionation of bone marrow cells before infection with A-MuLV demonstrates that the majority of A-MuLV-sensitive cells are recovered in a broad band partially overlapping the majority of the nucleated cells. The agarose assay system allows study of A-MuLV-lymphoid cell interaction at the level of single cell-single virus particle interaction

EFFECT OF LOW DOSE RADIATION ON DIFFERENTIATION OF BONE MARROW CELLS INTO DENDRITIC CELLS

Low dose radiation has been shown to be beneficial to living organisms using several biological systems, including immune and hematopoietic systems. Chronic low dose radiation was shown to stimulate immune systems, resulting in controlling the proliferation of cancer cells, maintain immune balance and induce hematopoietic hormesis. Since dendritic cells are differentiated from bone marrow cells and are key players in maintaining the balance between immune activation and tolerance, it may be important to further characterize whether low dose radiation can influence the capacity of bone marrow cells to differentiate into dendritic cells. We have shown that bone marrow cells from low dose- irradiated (γ-radiation, 0.2Gy, 15.44mGy/h) mice can differentiate into dendritic cells that have several different characteristics, such as expression of surface molecules, cytokine secretion and antigen uptake capacity, when compared to dentritic cells differentiated from the control bone marrow cells. These differences observed in the low dose radiation group can be beneficial to living organisms either by activation of immune responses to foreign antigens or tumors, or maintenance of self-tolerance. To the best of our knowledge, this is the first report showing that total-body low dose radiation can modulate the capacity of bone marrow cells to differentiate into dendritic cells

The Effect of Parental Bone Marrow & Spleen Cells in the Induction of the Graft-Versus-Host Reaction

Variously aged (C57BL X C3H)F1 hybrid mice were used as recipients in experiments to determine if spleen or bone marrow cells from normal C57BL or C3H donors, spleen or bone marrow cells from C57BL donors previously treated with cortisone, or C57BL bone marrow cells previously incubated with serum from X-irradiated C57BL mice could induce a graft-versus-host reaction (GVHR). The mice were assayed for GVHR by mortality or splenomegaly as detected by the discriminant spleen assay developed by Simonsen. Results show that spleen cells from normal C57BL, normal C3H, or cortisone-treated C57BL mice are capable of inducing a GVHR in F1 hybrids, resulting in death or splenomegaly, whereas bone marrow cells from normal C3H, normal C57BL, or cortisone-treated C57BL mice were unable to induce a GVHR in F1 hybrids. It was also found that sera from lethally irradiated C57BL mice did not cause C57BL bone marrow to induce a GVHR in F1 hybrids

CONTRIBUTION OF A THYMIC HUMORAL FACTOR TO THE DEVELOPMENT OF AN IMMUNOLOGICALLY COMPETENT POPULATION FROM CELLS OF MOUSE BONE MARROW

The hypothesis that cells located in mouse bone marrow can acquire immunological competence by a process that involves interaction with a noncellular component of the thymus was tested using an in vitro assay of graft-versus-host reactivity as a criterion of cell competence. When suspensions of C57BL bone marrow cells were incubated in thymus extract and injected into mice incapable of inducing a response in the graft-versus-host assay as a result of neonatal thymectomy, or adult thymectomy plus irradiation, or because of genetic similarity with the (C3H x C57BL)F1 tissue used for challenge in the assay, competent cells were recovered from the spleens of the injected mice. The reactive cells were shown to be of bone marrow origin since immune reactivity was related to the genetic makeup of the bone marrow cells rather than that of the intermediate recipients. A thymic factor was involved in the process leading to immune reactivity by these cells, as bone marrow cells incubated in xenogeneic or syngeneic thymic extracts induced a graft-versus-host response after passage through nonresponsive mice, whereas incubation of bone marrow cells in xenogeneic lymph node or spleen extracts or in culture medium only did not lead to subsequent reactivity. Participation of peripheral lymphoid tissue seemed essential in this process since bone marrow cells tested directly after exposure to thymic extract failed to induce a graft-versus-host response. C57BL bone marrow cells exposed to thymus extract and cultured together with fragments of (C3H x C57BL)F1 spleen tissue in vitro were competent to induce a graft-versus-host response; thus, these components would seem to be sufficient as well as necessary for the immunodifferentiation process leading to graft-versus-host activity. It is concluded that one step in the process by which bone marrow cells acquire competence vis-a-vis the graft-versus-host response depends upon a thymic agent that is noncellular and extractable, and that another stage in this process is under the influence of components found within the peripheral lymphoid tissue environment. It is suggested that differentiation of precursor cells to competence could occur by progressive development of the cells in separate compartments of the lymphoid system

Radiation Induced Apoptosis of Murine Bone Marrow Cells is Independent of Early Growth Response 1 (EGR1)

An understanding of how each individual 5q chromosome critical deleted region (CDR) gene contributes to malignant transformation would foster the development of much needed targeted therapies for the treatment of therapy related myeloid neoplasms (t-MNs). Early Growth Response 1 (EGR1) is a key transcriptional regulator of myeloid differentiation located within the 5q chromosome CDR that has been shown to regulate HSC (hematopoietic stem cell) quiescence as well as the master regulator of apoptosis—p53. Since resistance to apoptosis is a hallmark of malignant transformation, we investigated the role of EGR1 in apoptosis of bone marrow cells; a cell population from which myeloid malignancies arise. We evaluated radiation induced apoptosis of Egr1+/+ and Egr1-/- bone marrow cells in vitro and in vivo. EGR1 is not required for radiation induced apoptosis of murine bone marrow cells. Neither p53 mRNA (messenger RNA) nor protein expression is regulated by EGR1 in these cells. Radiation induced apoptosis of bone marrow cells by double strand DNA breaks induced p53 activation. These results suggest EGR1 dependent signaling mechanisms do not contribute to aberrant apoptosis of malignant cells in myeloid malignancies

STUDIES ON CHARACTERIZATION OF THE LYMPHOID TARGET CELL FOR ACTIVITY OF A THYMUS HUMORAL FACTOR

The immune response to SRBC was measured in the spleens of adult thymectomized, total body irradiated mice injected with various combinations of thymus and bone marrow cells together with thymic humoral factor (THF). It was found that the number of plaque-forming cells was significantly increased when THF was given in vivo immediately after thymus cell administration or when thymus cells were incubated in THF before injection. On the other hand, bone marrow cells equally treated did not manifest any T cell activity, since THF-treated bone marrow cells were not able to substitute thymus cells in the system used. The results accumulated in the present experiments indicate, therefore, that the target cells for THF activity are thymus cells which acquire a higher T helper cell capacity after THF treatment