Population dynamics of "null" and Thy1lo lymphocytes in mouse bone marrow: genesis of cells with natural killer cell lineage characteristics.

The population dynamics of "null" small lymphocytes lacking B and T lineage markers in mouse bone marrow have been examined using a combination of immunolabeling and hydroxyurea (HU) deletion techniques. The binding of the B lineage-associated mAb, 14.8, and anti-Thy1.2 to bone marrow cells has been detected radioautographically. Null cells lacking 14.8 and Thy1.2 determinants (14.8- Thy1-) formed a substantial subset (12-14%) of bone marrow small lymphocytes, representing 0.5 x 10(6) cells per femur (2-3% of nucleated cells). HU treatment revealed an exceptionally rapid turnover of the null small lymphocyte population (T1/2, 7.5 hr) compared with 14.8+ cells (T1/2, 20.5 hr) and Thy1+ cells (T1/2, 53 hr). Small lymphocytes bearing low intensities of Thy1 (Thy1lo) were also rapidly renewed (T1/2, 28 hr) whereas those with high intensities of Thy1 (Thy1hi) were renewed only slowly (T1/2, 123 hr). During ontogeny, null small lymphocytes first appeared in the fetal liver by Day 11 and the fetal spleen by Day 16, but increased rapidly in the bone marrow in early postnatal life. Double immunolabeling techniques demonstrated that 10% of null small lymphocytes in the bone marrow expressed NK1.1 antigen, while larger proportions bound to tumor (YAC.1) cells in vitro and displayed Fc receptors. The NK1.1-bearing fraction of null small lymphocytes in bone marrow was depleted by HU treatment only after an initial delay. NK1.1 was also expressed on subsets of Thy1lo cells and Thy1hi cells. The results have revealed the continuous production in mouse bone marrow of null and Thy1lo small lymphocytes, totaling 1-3 x 10(7) cells/day and 1.2 x 10(6) cells/day, respectively. The findings suggest that the large-scale production of null lymphocytes in mouse bone marrow includes the genesis of NK lineage cells which express NK1.1 and Thy1lo during a period of terminal maturation.     

Heterogeneity of NK1.1+ T cells in the bone marrow: divergence from the thymus.

NK1.1+ T cells in the mouse thymus and bone marrow were compared because some marrow NK1.1+ T cells have been reported to be extrathymically derived. Almost all NK1.1+ T cells in the thymus were depleted in the CD1-/-, beta2m-/-, and Jalpha281-/- mice as compared with wild-type mice. CD8+NK1.1+ T cells were not clearly detected, even in the wild-type mice. In bone marrow from the wild-type mice, CD8+NK1.1+ T cells were easily detected, about twice as numerous as CD4+NK1.1+ T cells, and were similar in number to CD4-CD8-NK1.1+ T cells. All three marrow NK1.1+ T cell subsets were reduced about 4-fold in CD1-/- mice. No reduction was observed in CD8+NK1.1+ T cells in the bone marrow of Jalpha281-/- mice, but marrow CD8+NK1.1+ T cells were markedly depleted in beta2m-/- mice. All NK1.1+ T cell subsets in the marrow of wild-type mice produced high levels of IFN-gamma, IL-4, and IL-10. Although the numbers of marrow CD4-CD8-NK1.1+ T cells in beta2m-/- and Jalpha281-/- mice were similar to those in wild-type mice, these cells had a Th1-like pattern (high IFN-gamma, and low IL-4 and IL-10). In conclusion, the large majority of NK1.1+ T cells in the bone marrow are CD1 dependent. Marrow NK1.1+ T cells include CD8+, Valpha14-Jalpha281-, and beta2m-independent subsets that are not clearly detected in the thymus.     

Isolation of rat bone marrow mast lineage cells using Thy 1.1 and rat stem cell factor.

Recent reports have shown that various marrow-derived cell populations respond vigorously to recombinant rat stem cell factor (rrSCF164), one form of the kit-ligand. In the present study, we isolated cell populations from rat bone marrow using the Thy 1.1 antigen (an antigen that in the rat is differentially expressed on primitive hemopoietic progenitor cells) and fluorescently conjugated rrSCF164 (rrSCF164-PE). We show that rrSCF164 only stimulates cells that are enriched in the brightest Thy 1.1 populations (Thy 1.1bright). Numerous cell lines were generated by serial passage in rrSCF164 containing medium, and the prototypic cell lines have been designated SRT002 and SRT003. Each cell line retains the Thy 1.1bright phenotype and does not respond to interleukins (IL) 1-8, IL-10, granulocyte (G) colony-stimulating factor (CSF), granulocyte macrophage (GM) CSF, M-CSF, or crude preparations of mitogen-stimulated T-cell supernatants. The Thy 1.1bright population of rat marrow was subdivided into a subset that binds rrSCF164-PE (Thy 1.1bright, rrSCF164+). The majority of these cells possess certain characteristics in common with marrow-derived mast cells and the Thy 1.1bright, rrSCF164 responsive cell lines, having similar granule morphology, being metachromatic, and reacting positively with alcian blue. Moreover, rats treated with rrSCF164 displayed significant increases in Thy 1.1bright, rrSCF164+ cells in the bone marrow. These studies show that the combination of Thy 1.1 and rrSCF164 makes possible the isolation of a unique subset of rat bone marrow cells that differentially express the Thy 1.1 antigen and the cell surface receptor c-kit, the majority of which are morphologically similar to marrow-derived mast cells.     

Development of intestinal intraepithelial lymphocytes, NK cells, and NK 1.1+ T cells in CD45-deficient mice

The transmembrane protein tyrosine phosphatase CD45 is differentially required for the development and function of B, T, and NK cells, with mice partially deficient for CD45 having a significant inhibition of T cell, but not NK or B cell, development. CD45-mediated signaling has also been implicated in the development of intrathymic, but not extrathymic, intestinal intraepithelial T lymphocytes (iIELs) in the CD45ex6(-/-) mouse. As NK1.1(+) CD3(+) (NK-T) cells can also develop through extrathymic pathways, we have investigated the role of CD45 in NK-T cell development. In mice with a complete absence of CD45 expression (CD45ex9(-/-)) the NK-T cell population was maintained in the iIEL compartment, but not in the spleen. Functionally, CD45-deficient NK-T cells were unable to secrete IL-4 in response to TCR-mediated signals, a phenotype similar to that of CD45-deficient iIELs, in which in vitro cytokine production was dramatically reduced. Using the CD45ex9(-/-) mouse strain, we have also demonstrated that only one distinct population of NK-T cells (CD8(+)) appears to develop normally in the absence of CD45. Interestingly, although an increase in cytotoxic NK cells is seen in the absence of CD45, these NK calls are functionally unable to secrete IFN-gamma. In the absence of CD45, a significant population of extrathymically derived CD8alphaalpha(+) iIELs is also maintained. These results demonstrate that in contrast to conventional T cells, CD45 is not required during the development of CD8(+) NK-T cells, NK cells, or CD8alphaalpha(+) iIELs, but is essential for TCR-mediated function and cytokine production.     

Effector cell expression of NK1.1, a murine natural killer cell-specific molecule, and ability of mice to reject bone marrow allografts

The rejection of Hh-1 incompatible bone marrow cells in irradiated mice is mediated by NK cells and is genetically regulated. We tested the role of the NK-specific gene, NK1.1, in regulating the rejection of allogeneic bone marrow cell grafts. NK1.1+ mice, that are known to display strong resistance against Hh-1 incompatible grafts, were crossed to H-2/Hh-1 identical NK1.1-, poor responder mice, and the progeny were backcrossed to the poor responder parent. The segregating mice were individually typed for their expression of NK1.1 and the ability to resist Hh-1 incompatible bone marrow cells (BMC). A strong correlation was noted between expression of NK1.1 and rejection of H-2d/Hh-1d BMC. Our results support the idea that NK1.1 is one of the genes responsible for strong resistance to Hh-1d (determinant 2) but not for Hh-1j (determinant 3) BMC grafts. We suggest that the NK1.1 molecule functions as an accessory molecule in the cellular interactions involving the recognition of Hh-1 determinants.     

Characterization of small lymphocytes in the bone marrow of mice after prolonged treatment with anti-IgM antibodies.

In mice treated with anti-IgM antibodies from birth, small lymphocytes in the bone marrow and spleen have been characterized by their incidence, surface markers, and turnover. Essentially complete elimination of IgM-bearing small lymphocytes followed injections of anti-IgM but this treatment did not deplete the IgM-negative small lymphocytes in the marrow. These IgM-negative cells also lacked other markers of B lymphocytes, such as receptors for Fc and complement; they failed to bind anti-mouse T-lymphocyte serum and they formed a rapidly renewing population within the marrow. This population may represent cells whose normal differentiation has been aborted by the anti-IgM antibodies or, alternatively, they may be “null” cells, distinct from B lymphocytes.     

Thy 1 expression in the brain of nude mice.

The expression and cell distribution of Thy 1 antigen was studied in the brain of both normal and athymic (nude) young adult mice of the BALB/c strain by immunochemistry. In nude animals Thy 1 fluorescence was less intense and less regularly distributed in the molecular layer of the cerebellum and hippocampus. Thy 1 content determined by ELISA was lower by 10-16% in the cerebellum and 20-25% in the olfactory bulbs of nude mice. The total wet weight of the brain was lower by 16% than in control animals; the deficit in body weight ranged from 34-45%. It is supposed that the changes in Thy 1 expression in nude animals are caused mainly by the underdevelopment of late developing brain regions due to thermoregulatory problems and other postnatal strains occurring in the mutants.     

The effect of indomethacin on the activation and effector function of suppressor cells from tumor-bearing mice

Summary The spleens of mice with large M-1 fibrosarcomas contain two populations of suppressor cells with the properties of macrophages and T cells. In this study, we tested the effect of indomethacin on suppressor cell activation and effector function. Neither the activation nor the effector function of the suppressor macrophages was inhibited by indomethacin, and the activity of suppressor macrophages correlated with the tumor size. In contrast, the treatment of tumor-bearing mice with indomethacin from the day of injection of tumor cells completely blocked the in vivo activation of suppressor T cells. Indomethacin did not, however, depress suppressor T cell activity if mice were treated only during the third week of tumor growth. The effector function of the suppressor T cells, as assessed in mixing assays, was partially blocked by indomethacin, while selective suppression by low-molecular-weight factors was completely blocked if indomethacin was present in the cultures. Furthermore, the in vitro activation of suppressor cells by soluble factors secreted by tumor-bearer spleen cells was completely blocked by indomethacin, and this inhibition was reversed by prostaglandin E₁. These data are consistent with the hypothesis that prostaglandins are involved in the activation, but not the effector function, of tumor-activated suppressor T cells.     

Thy1+ NK [corrected] cells from vaccinia virus-primed mice confer protection against vaccinia virus challenge in the absence of adaptive lymphocytes

While immunological memory has long been considered the province of T- and B-lymphocytes, it has recently been reported that innate cell populations are capable of mediating memory responses. We now show that an innate memory immune response is generated in mice following infection with vaccinia virus, a poxvirus for which no cognate germline-encoded receptor has been identified. This immune response results in viral clearance in the absence of classical adaptive T and B lymphocyte populations, and is mediated by a Thy1(+) subset of natural killer (NK) cells. We demonstrate that immune protection against infection from a lethal dose of virus can be adoptively transferred with memory hepatic Thy1(+) NK cells that were primed with live virus. Our results also indicate that, like classical immunological memory, stronger innate memory responses form in response to priming with live virus than a highly attenuated vector. These results demonstrate that a defined innate memory cell population alone can provide host protection against a lethal systemic infection through viral clearance.     

Radiosensitivity of clonogenic granulocytic macrophage cell precursors in the bone marrow and spleen of tumor-bearing mice

Clonogenic granulocytic macrophagal cells-precursors (CFU-DC) of bone marrow and spleen of intact C57Bl/6 mice and those inoculated subcutaneously with LLC tumor cells do not substantially differ in their radiosensitivity; the concentration of CFU-DC in the spleen markedly varies as tumor grows. The values of Do and extrapolation number n for CFU-DC of the bone marrow are 0.9-1.4 and 1.5-3.0 Gy, and of the spleen, 0.8-1.6 and 1.0-2.6 Gy, respectively.     

Protection against diabetes and improved NK/NKT cell performance in NOD.NK1.1 mice congenic at the NK complex

The NK1.1 cell surface receptor, which belongs to the NKR-P1 gene cluster, has been bred onto nonobese diabetic (NOD) mice for two purposes. The first was to tag NK and NKT cells for easier experimental identification of those subsets and better analysis of their implication in type 1 diabetes. The second was to produce a congenic strain carrying Idd6, a susceptibility locus that has been repeatedly mapped in the vicinity of the NKR-P1 gene cluster and the NK complex, to explore the impact of this locus upon autoimmune diabetes. NOD.NK1.1 mice express the NK1.1 marker selectively on the surface of their NK and NKT cell subsets. In addition, the mice manifest reduced disease incidence and improved NK and NKT cell performance, as compared with wild-type NOD mice. The association of those two features in the same congenic strain constitutes a strong argument in favor of Idd6 being associated to the NK complex. This could explain at the same time the multiple alterations of innate immunity reported in NOD mice and the fact that disease onset can be readily modified by boosting the innate immune system of the mouse.     

Radioautographic studies on the formation and maturation of bone marrow lymphocytes in mice

Abstract. DNA labelling by [³H]thymidine and the sandwich radioimmunolabelling method were used to characterize marrow lymphoid cells and to study the kinetics of production and maturation of small lymphocytes in the bone marrow of adult mice. Marrow lymphoid cells consisted of non-proliferating small lymphocytes, 30–40% of which had detectable surface immunoglobulin (SmIg), and proliferating large lymphoid cells lacking SmIg. Double-labelling experiments employing [³H]thymidine in vivo followed by sandwich radioimmunolabelling in vitro indicated that marrow small lymophocytes lack detectable SmIg when they are formed but develop SmIg within the first few days after production. Marrow lymphocytopoiesis includes; (1) praliferation of large lymphoid cells, which are presumptive small lymphocyte progenitors, which have a cell cycle time of 14–15 hr, and (2) a 3–5-day intramyeloid stage when many newly formed small lymphocytes undergo maturational changes towards the B cell lineage.     

Evidence for the presence in unimmunized mice of two populations of bone marrow derived B lymphocytes, defined by differences in adherence properties

The presence of two populations of bone-marrow-derived lymphocytes in normal unimmunized mice was inferred from data showing that cells forming antibody to either the dinitrophenyl (DNP) determinant or sheep erythrocytes (SRC) arose spontaneously in antigen-free tissue culture medium in contrast to cells forming antibody against FγG, which arose spontaneously in much smaller numbers, and which in cultures of spleen cells from the athymic (nude) mouse were undetectable. Measures amplifying the degree of spontaneous activation of antibody forming cells (AFC) to DNP and SRC, such as the inclusion in cultures of large doses of polymerized flagellin (POL) or flagella (FLA), lipopolysaccharide (LPS) or the presence of allogeneic cells had no effect on the absence of nonantigen dependent activation of FγG-reactive B cells. However when appropriately activated, by FγG plus a “second signal” provided by the presence of POL, FγG-reactive B cells became fully susceptible to the effect of the presence of allogeneic cells in amplifying the numbers of AFC produced in cultures.An ancillary observation suggested that a proportion of B cells reactive to DNP and SRC from CBA mice passed through macrophage adherence columns, while only a small percentage of B cells reactive to FγG could be demonstrated in the filtrate.An hypothesis accounting for these observations is that the population of B cells reactive to FγG, the activation of which is absolutely antigen dependent, differs from a proportion of the population of B cells reactive to DNP and SRC in that this proportion of the latter populations has been altered by previous activation by cross-reacting antigens. The spontaneous appearance of non antigen dependent AFC to DNP and SRC in tissue culture, and the increase in this number induced by a factor produced by allogeneic recognition, are a functional reflection of such an alteration by previous contact with antigen. It seems possible that a loss of a tendency of the virgin B cell to adhere to glass or plastic is another consequence of prior interaction with antigen.     

Morphological changes in spleen, bone marrow and blood of rats after continuous gamma irradiation and indomethacin treatment.

A possibility of modifying the radiation damage of haematopoiesis by indomethacin administered during continuous irradiation was followed. Indomethacin was given in drinking water (average dose of 740.7 micrograms/kg per day) within 7-days continuous irradiation with gamma rays (a daily dose rate of 2.055 Gy, total accumulated dose of 14.385 Gy). Under the given conditions no marked protective effect of indomethacin on haematopoiesis was found with the exception of mild stimulation of myelopoiesis and an increased release of developmentally younger cells of myeloid and erythroid series to the peripheral blood as well.     

Regulation of lymphocyte production in the bone marrow. I. Turnover of small lymphocytes in mice depleted of B lymphocytes by treatment with anti-IgM antibodies

To examine the concept that the genesis of lymphocytes in the bone marrow may be regulated by homeostatic feedback signals from peripheral B lymphocytes or their products, lymphocyte production was measured in mice selectively depleted of B lymphocytes by repeated administration of anti-IgM antibodies from birth. The turnover of small lymphocytes was quantitated radioautographically after DNA labeling by continuous infusion of 3H-thymidine. In the femoral marrow of anti-IgM-treated mice, the number of small lymphocytes was reduced and their turnover time was shorter than in control mice, presumably reflecting the premature elimination from the marrow of maturing cells about to express surface IgM. The absolute number of small lymphocytes being produced per femur in unit time, however, was identical in anti-IgM-treated and control mice. Lymphocyte production in the thymus was also unaffected by anti-IgM suppression whereas in the spleen the turnover of small lymphocytes was reduced due to the lack of young immigrant B lymphocytes from the bone marrow. The results demonstrate that the normal large-scale production of lymphocytes in mouse bone marrow is independent of the magnitude of the peripheral pool of B lymphocytes or the level of circulating immunoglobulins, suggesting the process is not subject to feedback control. Some implications for the genesis and diversity of primary B lymphocytes are discussed.     

Unusual T cell populations in adult murine bone marrow. Prevalence of CD3+CD4-CD8- and alpha beta TCR+NK1.1+ cells

The T cell populations present in normal murine bone marrow have not been previously analyzed in detail, mainly because of their relative rarity. In order to permit such analyses, bone marrow T cells were enriched by depleting Mac1-positive cells, which constitute 65 to 90% of bone marrow cells (BMC), and then studied by two-color flow cytometry. Analysis of the remaining cells revealed that the T cell profile of adult murine bone marrow is markedly different from that of other lymphoid organs. A very high proportion of bone marrow CD3+ cells (approximately one-third) are CD4-CD8-. CD3+CD4-CD8- cells are much more concentrated among BMC T cells than among thymocytes or splenic T cells, suggesting that bone marrow may be either a site of extrathymic TCR gene rearrangement, or a major site to which such cells home from the thymus. The expression of NK1.1 was also evaluated on Mac1-depleted BMC populations. Surprisingly, up to 39% of alpha beta TCR+ BMC were found to express NK1.1. Most alpha beta TCR+NK1.1+ BMC also expressed CD4 or CD8. NK1.1+ alpha beta TCR+ cells represented a much greater proportion of BMC T cells than of other lymphoid (splenocyte or thymocyte) T cell populations. Mac1-depleted BMC of nude mice contained very few cells with this phenotype. These results are consistent with the hypothesis that NK1.1+ alpha beta TCR+ cells are generated primarily in the thymus of normal animals and migrate preferentially to bone marrow, where they may function as regulatory elements in hematopoiesis.     

In vitro and in vivo analysis of bone marrow-derived CD3+, CD4-, CD8-, NK1.1+ cell lines

The development of methods of avoiding graft-versus-host disease (GVHD) while retaining the alloengraftment-promoting and anti-leukemic effects of allogeneic T cells is a major goal of research in bone marrow transplantation (BMT). We have recently obtained evidence suggesting that natural suppressor (NS) cells derived from T cell-depleted (TCD) syngeneic marrow can protect against GVHD while permitting alloengraftment. We have now attempted to enrich and then propagate NS cells in vitro, with the goal of obtaining an enhanced anti-GVHD effect by adoptive transfer in vivo. Two long-term cell lines were generated culturing BMC depleted of Mac1-positive cells and of Mac1-positive plus Thy1-positive cells in high concentrations of IL-2. Both cell lines showed anti-GVHD effects when administered along with a GVHD-producing inoculum, while permitting complete allogeneic reconstitution. A clone derived from Mac1-depleted BMC protected completely against a more chronic pattern of GVHD. These cell lines demonstrated suppressive activity in vitro, cytolytic activity against a broad range of natural killer (NK)-sensitive and NK-resistant targets, and a novel cell surface phenotype, with characteristics of both alpha beta-TcR-bearing T cells and of NK cells. In some respects, these cells resemble LAK cells and differ from fresh NS cells, and from the cloned NS cells derived from spleens of total lymphoid irradiation (TLI)-treated mice and neonatal mice. To our knowledge, this is the first detailed phenotypic analysis of cell lines with in vivo anti-GVHD activity. If applicability can be demonstrated in large animal models, the ability to use bone marrow as a source of such protective cell lines might also have potential utility in clinical BMT.     

The effect of splenectomy on bone marrow haematopoiesis in mice.

Splenectomy was performed in strain H mice. Erythrocyte macrocytosis and an increase in the reticulocyte, leucocyte and thrombocyte count were found in the peripheral blood of splenectomized animals; only the erythrocyte count fell in the first 3 weeks after splenectomy. Changes in the myelogram during the first weeks after splenectomy were characterized by an increase in the proportion of cells of the erythrocytic and lymphocytic series. The stem cell count in the bone marrow (determined after Till and McCulloch) was slightly elevated on the 8th day after splenectomy, but in subsequent weeks was rather lower than the control group values. Whatever the post-splenectomy interval at which bone marrow was taken from splenectomized mice, there was no significant difference in the transplantation effect of bone marrow cells on white and thrombocyte haematopoiesis. Bone marrow transplantation was found have a stimulant effect only on the reticulocyte count and the sooner bone marrow was collected after splenectomy, the more pronounced the effect. Changes in the myelogram and splenogram of irradiated mice to which the bone marrow cells of splenectomized mice had been transplanted were relatively small.