STROMAL CHANGES IN LEUKAEMIC AND RELATED BONE MARROW PROLIFERATIONS

The stromal structure of the bone marrow was studied in 96 cases of leukaemia and related disorders. The reticulin stroma forms an integral component of any given marrow proliferation and may often be increased in amount, sometimes normal, and occasionally decreased. The pattern is often indeterminate but certain distinguishable patterns may be found, including a sinusoidal pattern in myelofibrotic chronic myeloses, a pattern characterized by an abundance of hyperplastic capillaries and arterioles often seen in lymphoid leukaemias, and one with irregular focal reticulin proliferation in many acute undifferentiated leukaemias.Adventitious collagen fibres are demonstrable in about half of all myeloses, acute and chronic, leukaemic and aleukaemic, and may be diffuse or focal. They apparently develop from thickening and collapse and condensation of the basic reticulin network, not from any primary fibroblastic proliferation. The development of fibrosis does not denote an aetiological relationship between the conditions in which it occurs, since it appears to be a non-specific sequel to marrow exhaustion and marrow necrosis. There is no justification for the diagnosis of acute or ;malignant' myelofibrosis as a disease entity in cases of acute leukaemia with marrow fibrosis.Osteolytic change due to resorption of bony trabeculae is a common event in all the conditions studied and may be accompanied by remoulding of the eroded trabeculae. Fibre bone formation is found in about 15% of cases, including acute lymphoblastic leukaemias and acute undifferentiated leukaemias, but is extensive and well-developed only in cases of primary myelofibrosis.

STUDIES ON IN VITRO ANTIBODY PRODUCTION. 3. PRODUCTION OF COMPLEMENT

Bone marrow, spleen, liver, and thymus cells of the guinea pig were incubated in Eagle"s minimal essential medium which contained glycine-2-C14. Flasks were removed from the water bath at 0, 6, 18, 24, and 48 hours and their contents were homogenized, centrifuged, and concentrated. Experiments were carried out with the concentrated supernatant samples to determine whether or not they contained proteins with properties similar to those of complement (C′) proteins. Titrations for hemolytic activity revealed that bone marrow cells produced C′2, C′3, and C′4; spleen cells synthesized C′2 and liver slices produced C′2. Liver supernatant samples also contained C′3 activity, but proteins associated with C′3 actiyity seemed to be released rather than synthesized by liver slices. We were unable to demonstrate C activity with thymus cell supernatants. Heat inactivation (56 °C for 30 minutes), as well as EDTA inhibited the hemolytic activity of supernatant samples.Further experiments showed that these supernatant proteins were fixed to antigen–antibody complexes and to aggregated gamma-globulin. The fixation was inhibited by guinea pig serum. Immunoelectrophoresis and gel-diffusion showed that proteins synthesized in vitro migrated as beta-globulins and were antigenically similar to C′ proteins.

THE STIMULATION OF DNA SYNTHESIS IN CULTURES OF RABBIT LYMPH NODE AND SPLEEN CELL SUSPENSIONS BY HOMOLOGOUS CELLS

An early proliferative response follows the mixing of homologous spleen or lymph node suspensions obtained from two unrelated rabbits. The rate of incorporation of radioactive thymidine has been used as a quantitative measure of this response. Thymus cells do not respond to homologous cell suspensions but may on occasion serve to stimulate the response in homologous spleen or lymph node cells. Homologous erythrocytes or autologous tissues do not stimulate a response. No response occurs if the two cell populations are separated by a Millipore membrane. Autoradiographic studies have established that 1 to 2 per cent of the intial cell population is involved in the response and they are large undifferentiated cells by the time they can first be identified as responders. There was no morphological evidence of any cellular interaction and the viability of mixed suspensions was not measurably different from that observed in separate suspension. Simultaneous additive responses could be obtained to homologous cells and to antigen when cell suspensions from immunized rabbits were used. The interaction of the cell populations from the two rabbits did not appear to suppress the response of each to antigen. The speed and magnitude of the response were in everyway comparable with the secondary response of cell suspensions from immunized rabbits exposed to the immunizing antigen. No evidence was obtained of any enhancement of the response to homologous cells by prior immunization with homologous tissues, but the possibility that it had occurred was not rigidly excluded.

ALTERATIONS IN POLYRIBOSOMES DURING ERYTHROID CELL MATURATION

This communication presents a morphological study of the changes in ribosome content and organization which occur during the maturation of erythroid cells of the phenylhydrazine-treated rabbit. Electron micrographs of thin sectioned nucleated and non-nucleated erythroid cells have been subjected to a quantitative analysis of the distribution of ribosomes as polyribosomes of various sizes and as single ribosomes. The ribosomes of nucleated erythroid cells of marrow are virtually all arranged in the polyribosome configuration consisting of clusters of 2 to 6 individual ribosomes. These cells are the most active in the erythroid series in protein biosynthesis. During maturation to the non-nucleated reticulocyte stage, found in the circulating blood, there is a decrease in protein synthesizing capacity, a fall in total ribosome content, and, more significantly, a decrease in the number and size of polyribosomes. Maturation to the ribosome-free erythrocyte, either under in vitro or in vivo conditions, entails a further decrease in protein synthesis which correlates with a progressive disaggregation of the biosynthetically active polyribosomes into smaller clusters and inactive single ribosomes. Possible models which may account for the stability of the polyribosome and for the mechanism of polyribosome dissociation are discussed.

STUDIES IN EXPERIMENTAL EOSINOPHILIA. VI. UPTAKE OF IMMUNE COMPLEXES BY EOSINOPHILS

A method is described whereby immune complexes may be visualized in a single cell. Bovine serum albumin labeled with a red-fluorescing dye was joined to a rabbit antiserum labeled with a green-fluorescing dye to yield an immune complex which fluoresced yellow when illuminated by ultraviolet light. Such yellow-fluorescing immune complexes were injected into the peritoneal cavity of guinea pigs, and the peritoneal exudates were examined subsequently. Yellow fluorescent particles were seen in eosinophils obtained from guinea pigs sensitized to hemocyanin and from normal animals. Eosinophils of the blood and of the bone marrow could also take up the complexes in vitro. Neither antigen nor antibody alone was taken up by eosinophils, nor was a mixture of labeled antigen and labeled normal globulin. Similar observations were made with human blood eosinophils. These experiments suggest that eosinophils act as part of the defense against the pathogenic effects of certain immune complexes.

HISTOCHEMICAL DEMONSTRATION OF GAMMA GLUTAMYL TRANSPEPTIDASE ACTIVITY IN BONE MARROW AND BLOOD CELLS

The demonstration by a histochemical method of gamma glutamyl transpeptidase is described. In marrow and peripheral blood it has been found useful in differentiating between normal and leukaemic myeloblasts and between marrow (short-lived) lymphocytes and lymph node (long-lived) lymphocytes. The method may also be of value in differentiating between normal and neoplastic cells.

ANTI-DNA ANTIBODIES IN HYPERIMMUNIZED RABBITS

Complement-fixing anti-DNA antibodies were detected in a minority of sera of rabbits hyperimmunized with killed Gram-negative bacteria. The C'-fixing property of DNA was lost after DNase treatment. Preferential reactivity with denatured DNA was observed. The antisera reacted with DNA preparations derived from rabbit bone marrow and thymus, calf thymus, pneumococci, salmon sperm, and Escherichia coli. E. coli DNA was less effective than preparations of mammalian and salmon sperm DNA in fixation of C'. Inhibition of DNA C' fixation by nucleotides and nucleosides was observed. The bulk of anti-DNA activity was associated with the low molecular weight antibody fraction.

ULTRASTRUCTURE OF A MYCOPLASMA (NEGRONI) ISOLATED FROM HUMAN LEUKEMIA

Hummeler, Klaus (The Children's Hospital of Philadelphia, Philadelphia, Pa.), Natale Tomassini, and Leonard Hayflick. Ultrastructure of a mycoplasma (Negroni) isolated from human leukemia. J. Bacteriol. 90:517-523. 1965.-A strain of mycoplasma isolated in tissue cultures from human leukemic bone marrow was cultivated in cell-free media for 23 passages. Concentrates of broth cultures were investigated under the electron microscope in thin sections and negative contrast. The ultrastructure of the mature mycoplasma cells and their elementary bodies is described. It was found that the elementary bodies, particularly in the negative contrast preparations, bear a close resemblance to viruslike particles seen in tissues and plasmas of leukemic patients.