Regulation of B-lymphocyte production in the bone marrow: mediation of the effects of exogenous stimulants by adoptively transferred spleen cells

Unusual malignant neoplasms occurring around dental implants: A report of 2 cases

Osseointegrated implants are now commonplace in contemporary dentistry. However, a number of complications can occur around dental implants, including peri-implantitis, maxillary sinusitis, osteomyelitis, and neoplasms. There have been several reports of a malignant neoplasm occurring adjacent to a dental implant. In this report, we describe 2 such cases. One case was that of a 75-year-old man with no previous history of malignant disease who developed a solitary plasmacytoma around a dental implant in the left posterior mandible, and the other was that of a 43-year-old man who was diagnosed with squamous cell carcinoma adjacent to a dental implant in the right posterior mandible. Our experiences with these 2 cases suggest the possibility of a relationship between implant treatment and an inflammatory cofactor that might increase the risk of development of a malignant neoplasm.

Regulation of cell survival during B lymphopoiesis in mouse bone marrow: enhanced pre-B-cell apoptosis in CSF-1-deficient op/op mutant mice

OBJECTIVE

Osteopetrotic (op/op) mice are deficient in macrophages and osteoclasts due to a CSF-1 gene mutation. The aim of this study was to evaluate the effect of these deficiencies and of CSF-1-dependent mechanisms on B lymphopoiesis in bone marrow, with special reference to the apoptotic activity of precursor B cells.

MATERIALS AND METHODS

B-cell development and apoptosis were examined in the bone marrow of op/op mice using immunofluorescence labeling and flow cytometry. Short-term cultures of bone marrow were used to evaluate the effect of recombinant CSF-1 on the rate of B-cell apoptosis.

RESULTS

Bone marrow cellularity was greatly reduced in op/op mice compared with normal littermates. However, precursor B cells were disproportionately decreased, most markedly at the pre-B-cell stage. Precursor B cells, particularly pre-B cells, displayed elevated apoptotic incidences both ex vivo and in short-term culture. Addition of recombinant CSF-1 reduced the incidence of apoptosis among precursor B cells in short-term cultures of whole bone marrow suspensions from normal mice but not in cultures of sorted B220+ B-lineage cells.

CONCLUSIONS

The finding of increased pre-B-cell apoptosis in op/op mice provides evidence that CSF-1-dependent mechanisms can strongly influence the survival of precursor B cells in mouse bone marrow, particularly at the pro-B/pre-B cell transition. It is proposed that the local or systemic levels of CSF-1 during ontogeny may thus play a role in regulating B-cell production within the bone marrow microenvironment.

Lifespan of lymphocytes

T and B lymphocytes comprise heterogeneous populations of cells at various stages of differentiation and activation. T- and B-cell subsets have different roles in the maintenance of immune homeostasis, and their functional differences are reflected by their respective lifespans. This review briefly summarizes the available data on lymphocyte lifespan, including the kinetics of T- and B-cell development in the primary lymphoid organs and the proliferative behavior of naive, effector and memory lymphocytes in the peripheral lymphoid compartment.

Insulin as a target antigen in autoimmune diabetes: a natural repertoire as the source of antibody response

A solid-phase immunoenzymatic technique with B1- or B29-biotinylated insulin coupled to avidin-coated wells was used to characterize serum anti-insulin antibodies and to locate insulin antibody-producing B lymphocytes in different organs of mice. Low natural serum anti-insulin IgM and IgG antibodies were found in ten different healthy inbred strains of mice. Prediabetic non-obese diabetic (NOD) mice had significantly higher measurements than BALB/c mice (P < 0.05). Anti-insulin IgM antibody-producing B lymphocytes were found in bone marrow and spleen of NOD mice and healthy strains of mice, but not in peripheral lymph nodes, thymus, blood or pancreas. B29-fixed insulin was more frequently recognized than B1-fixed insulin. There was no relationship to the MHC or to other immune markers. IgG insulin antibody-producing cells were not detected. IgG insulin antibody-producing cells appeared in the draining lymph node and in the blood 10 days after immunization with insulin. IgM insulin-recognizing cells in the spleen were reduced in number during the same period (P < 0.05-0.01 for BALB/c, DBA2, B10.D2 and NOD), suggesting migration of these cells. This was tested by in vivo staining of spleens with the red-fluorescent membrane linker PKH-26 on day 7 after immunization. Cells from immunized lymph nodes were FACS-sorted on day 10. Insulin antibody-producing B lymphocytes with red-fluorescence were found, indicating a splenic origin. Examination of IgG subclasses showed preferential production of complement-fixing IgG2b in sera and lymph node cells of immunized NOD mice (P < 0.05 vs BALB/c).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of ethanol consumption and withdrawal on B cell subpopulations in murine bone marrow

We designed studies to examine the effects of ethanol consumption and withdrawal on the numbers of pre-B and B cells in murine bone marrow. Flow cytometric analysis of B220 and surface IgM expression on bone marrow cells revealed that consumption of ethanol by mice for 7 days led to a significant reduction in pre-B cells. The number of mature B cells in the bone marrow of these animals, however, did not differ from that of control mice. In contrast, examination of bone marrow obtained from mice at various times after withdrawal from ethanol showed significantly fewer numbers of mature B cells and an even greater loss of pre-B cells. This effect was seen for relatively long periods after withdrawal. These study findings are interpreted to suggest that ethanol consumption results in changes in the pre-B cell population in murine bone marrow. It also appears that withdrawal from ethanol results in more profound changes in the mature B cell population of the bone marrow than those that occur during ethanol consumption.

Changes in the populations of null, NK1.1+, and Thy1lo lymphocytes in the bone marrow of tumor-bearing mice: Effect of indomethacin treatment

Mouse bone marrow produces many "null" lymphocytes which lack B and T lineage markers (B220-Thy1-). A subset of these cells expresses the natural killer (NK) cell marker, NK1.1. In addition, some rapidly renewed bone marrow lymphocytes express low intensities of Thy1 (Thy1lo). In view of their possible implication in tumor-host interactions these various cell populations have now been examined in mice injected with either the nonmetastatic Ehrlich ascites (EA) tumor or the Lewis lung carcinoma (LLc), a highly metastatic solid tumor. In each case, the number of null lymphocytes, as defined by a lack of radioautographic labeling of either B220 glycoprotein or Thy1, increased markedly in both the bone marrow and spleen. Treatment with the prostaglandin inhibitor, indomethacin, enhanced the increase in null cells in the bone marrow and spleen of LLc-bearing mice. The number of null small lymphocytes expressing NK1.1, as detected by combined radioautographic and immunoperoxidase techniques, increased almost 30-fold in LLc-bearing mice. The number of Thy1lo small lymphocytes increased in parallel with null cells during EA tumor growth. The findings accord with the hypothesis that the null lymphocyte population produced in mouse bone marrow includes newly formed NK lineage cells which sequentially express NK1.1 and Thy1lo. The present work demonstrates that the populations of null, NK1.1+, and Thy1lo lymphocytes in mouse bone marrow expand rapidly during the early growth of transplanted tumors, the initial increase in null lymphocytes apparently being curtailed by prostaglandin production. The results suggest that the production of null lymphocytes in mouse bone marrow is responsive to tumor development, possibly providing cells to be involved in tumor-host interactions.

Regulation of early precursor B cell proliferation in mouse bone marrow: stimulation by exogenous agents mediated by macrophages in the spleen

An increase in pre-B cell proliferation and B lymphocyte production in mouse bone marrow has previously been shown to follow the administration of various foreign agents in vivo. The responses of early precursor B cells before the expression of mu chains (pro-B cells) have now been examined, using double immunofluorescence labeling for terminal deoxynucleotidyl transferase (TdT) and B220 glycoprotein as detected by monoclonal antibody 14.8. A single injection of sheep red blood cells (SRBC) was followed by an increase in the number of cells in three defined populations of early precursor B cells lacking mu chains (TdT+ 14.8- cells, TdT+ 14.8+ cells, and 14.8+ mu- cells) as well as cytoplasmic mu-bearing pre-B cells and surface mu-bearing B lymphocytes. An accompanying increase in proliferative activity was indicated by the numbers of 14.8+ mu- cells and pre-B cells which accumulated in metaphase after inducing mitotic arrest with vincristine. These effects were all abrogated either by treating mice with silica to depress macrophage function or by splenectomy. In mice given multiple injections of SRBC for 4 weeks the elevated levels of early precursor B cell production and B cell genesis were sustained. The work demonstrates that the in vivo production of early precursor B cells, putatively including those at the stage of Ig heavy chain gene rearrangement, can be stimulated by exposure to external agents acting indirectly by a silica-sensitive, spleen-dependent mechanism. The findings suggest that the level of pro-B cell proliferation and primary B cell genesis normally taking place in mouse bone marrow may reflect the level of exposure to potential stimulants in the external environment mediated by activation of splenic macrophages. The possibility that abnormally high levels of macrophage activation could predispose to dysregulations of the B cell lineage is raised.

Proliferation of B cell precursors in bone marrow of pristane-conditioned and malaria-infected mice: implications for B cell oncogenesis

Two widely different agents implicated in the etiology of neoplasias of the B cell lineage, pristane and malaria, have both been found to produce a prolonged increase in the level of proliferative activity and cell production by early B lymphocyte precursor cells in mouse bone marrow. This apparently leads to an elevated level of cell loss, suggesting the production of many aberrant early cells. The mechanism and significance of this effect remain to be determined. However, the present findings focus attention on the early stages of B cell genesis in the bone marrow as possible target cells for the initiation of genetic events leading to neoplasia. Together with previous work, the results suggest that pathologically elevated levels of macrophage activation may play a role in predisposing to various B cell neoplasias.

Dynamics of early B lymphocyte precursor cells in mouse bone marrow: proliferation of cells containing terminal deoxynucleotidyl transferase

Three populations of early B lymphocyte precursor cells lacking mu heavy chains have been defined in mouse bone marrow, based on immunofluorescence labeling for terminal deoxynucleotidyl transferase (TdT) and B220 glycoprotein, as detected by monoclonal antibody 14.8 (TdT+14.8- cells; TdT+14.8+ cells; TdT-14.8+ cells). We have now analyzed the frequency, size distribution, proliferation and production rates of TdT+ cells in mouse bone marrow. These formed well-defined populations of medium-sized cells, the TdT+14.8+ cells tending to be larger than TdT+14.8- cells (modal cell diameters in cytocentrifuge preparations; 10.0 microns and 9.0 microns, respectively). Some TdT+ cells (1%-2%) were normally in metaphase, the TdT being dispersed through the cytoplasm. After inducing mitotic arrest with vincristine, the incidence of TdT+ cells in metaphase increased linearly from 2 to 4 h, indicating a turnover of 5.1%/h for TdT+14.8- cells and 9.0%/h for TdT+14.8+ cells. Subtraction of turnover data for TdT+14.8+ cells from those previously obtained for 14.8+ mu- cells gave values for the population of TdT-14.8+ cells. The calculated daily turnover of cells in the three compartments increased progressively (TdT+14.8-, 2.5 x 10(6) cells; TdT+14.8+, 5.0 x 10(6) cells; TdT-14.8+, 36.0 x 10(6) cells), accompanied by a shortening of the average apparent cell cycle time (TdT+14.8-, 20 h; TdT+14.8+, 11 h; TdT-14.8+, 8 h). The results demonstrate a progressive expansion of cell production at three putatively successive stages of early B lymphocyte development before the expression of mu chains. The findings contribute to a kinetic model of primary B cell genesis in mouse bone marrow.