Basophils Trigger Fibroblast Activation in Cardiac Allograft Fibrosis Development.

Fibrosis is a major component of chronic cardiac allograft rejection. Although several cell types are able to produce collagen, resident (donor-derived) fibroblasts are mainly responsible for excessive production of extracellular matrix proteins. It is currently unclear which cells regulate production of connective tissue elements in allograft fibrosis and how basophils, as potential producers of profibrotic cytokines, are involved this process. We studied this question in a fully MHC-mismatched model of heart transplantation with transient depletion of CD4(+) T cells to largely prevent acute rejection. The model is characterized by myocardial infiltration of leukocytes and development of interstitial fibrosis and allograft vasculopathy. Using depletion of basophils, IL-4-deficient recipients and IL-4 receptor-deficient grafts, we showed that basophils and IL-4 play crucial roles in activation of fibroblasts and development of fibrotic organ remodeling. In the absence of CD4(+) T cells, basophils are the predominant source of IL-4 in the graft and contribute to expansion of myofibroblasts, interstitial deposition of collagen and development of allograft vasculopathy. Our results indicated that basophils trigger the production of various connective tissue elements by myofibroblasts. Basophil-derived IL-4 may be an attractive target for treatment of chronic allograft rejection.

Activation of basophils by the double-stranded RNA poly(A:U) exacerbates allergic inflammation.

BACKGROUND: It is commonly acknowledged that asthma is exacerbated by viral infections. On the other hand, basophil infiltration of lung tissues has been evidenced postmortem in cases of fatal disease, raising the question of a possible link between these two observations. OBJECTIVES: Herein, we addressed the relationship between asthma exacerbation by viral infection and basophil activation and expansion by investigating how stimulation with the dsRNA polyadenylic/polyuridylic acid [poly(A:U)] affected basophil activities and recruitment in an allergic airway inflammation model. METHODS: The effect of dsRNA on basophils was assessed by measuring the cytokine levels produced upon stimulation. We used an OVA-induced experimental model of allergic asthma. Airway hyperreactivity, recruitment of infiltrating cells, and cytokine production were determined in the lung of mice having received poly(A:U), as compared with untreated controls. The exacerbating effect of basophils was assessed both by adoptive transfer of poly(A:U)-treated basophils and by their in vivo depletion with Ba103 antibody. RESULTS: We found that in vitro treatment with poly(A:U) increased basophil functions by inducing TH 2-type cytokine and histamine production, whereas in vivo treatment increased peripheral basophil recruitment. Furthermore, we provide the first demonstration for increased infiltration of basophils in the lung of mice suffering from airway inflammation. In this model, disease symptoms were clearly exacerbated upon adoptive transfer of basophils exposed to poly(A:U), relative to their unstimulated counterpart. Conversely, in vivo basophil depletion alleviated disease syndromes, thus validating the transfer data. CONCLUSIONS: Our findings provide the first evidence for airway inflammation exacerbation by basophils following dsRNA stimulation.

Newly appreciated roles for basophils in allergy and protective immunity.

Basophils are evolutionarily conserved in many animal species, in spite of the fact that they account for <1% of peripheral blood leukocyte. This suggests that basophils have an indispensable and nonredundant role in vivo, even though they show some phenotypic similarity with tissue-resident mast cells. However, their functional significance remained uncertain long after Paul Ehrlich discovered them as blood-circulating cells with basophilic granules more than 130 years ago. The study of basophils has been far behind that of mast cells, owing to the rarity of basophils and the paucity of tools for their detection and functional analysis. Recent development of novel analytical tools, including basophil-depleting antibodies and genetically engineered mice deficient only in basophils, has greatly advanced basophil research and illuminated previously unrecognized roles of basophils. We now appreciate that basophils and mast cells play distinct roles in immune responses. Basophils have crucial roles in the development of acute and chronic allergic responses, the protective immunity against ecto- and endoparasites, and the regulation of acquired immunity, including the augmentation of humoral memory responses and the initiation of Th2 responses. Thus, basophils are no longer the neglected minority and are key players in the immune system.

The proteins encoded by the VpreB and lambda 5 pre-B cell-specific genes can associate with each other and with mu heavy chain.

The murine pre-B cell-specific genes VpreB and lambda 5, as well as the murine gene for mu heavy chain, were introduced into Ltk- fibroblast cells which normally do not express these genes. Stable transfectants carrying these genes produced the corresponding proteins of 15.5, 21.5, and 75 kD. They secreted the three proteins as a triple complex that could be immunoprecipitated by mu heavy chain-specific antibodies, consisting of one VpreB, one lambda 5, and one mu heavy chain. The mu heavy chain and lambda 5 were disulfide-bonded with each other, while the VpreB protein was noncovalently associated. These experiments proved that the VpreB, lambda 5 and mu H chain proteins can form a heavy/light chain-like heterocomplex.

Growth autonomy and tumorigenicity of interleukin 6-dependent B cells transfected with interleukin 6 cDNA.

We introduced an IL-6 cDNA expression vector into a murine B cell line, the growth of which definitely required the presence of exogenous IL-6. The transfected cells secreted substantial amounts of IL-6, to which they themselves responded by proliferating without further requirement of exogenous IL-6. The proliferation was a direct function of cell density and was inhibitable by antibodies to IL-6, indicating the autocrine nature of the growth. The IL-6 cDNA-transfected cells displayed greatly enhanced tumorigenicity when inoculated into syngeneic and nude mice. Our data suggest that an IL-6 autocrine self stimulation confers on B cells a selective growth advantage and results in the induction of progression of the malignant state of B cells.

Recombinant interleukin 2 or 5, but not 3 or 4, induces maturation of resting mouse B lymphocytes and propagates proliferation of activated B cell blasts.

Plasmacytoma transformants of the X63-Ag8-653 cell line carrying an expression vector with either IL-2, -3, -4, or -5 cDNA were established that secrete the corresponding ILs at high rates. The four mouse ILs (mILs) were then tested as single ILs and in combinations for their effects on the maturation of resting and proliferation of activated normal mouse splenic B cells. mIL-3 and mIL-4 were inactive in all assays. mIL-2, as well as mIL-5, synergized with Ig-specific antibodies and B cell growth factor alpha (BCGF-alpha) to stimulate successive rounds of B cell division with LPS-activated B cells. This activity as BCGF-beta was effective at concentrations similar to those at which mIL-2 induced proliferation of the CTL-L T cell line, indicating a high-affinity interaction of both mIL-2 and mIL-5 with their corresponding receptors on activated B cells. mIL-5 and maybe IL-2 also induced maturation of resting B cells to Ig-secreting cells without proliferation. This B cell maturation factor (BMF) activity of mIL-5 was as effective as its BCGF-beta activity, while the BMF activity of mIL-2 was at least 10(2)-fold less effective. BMF activity of mIL-2, but not mIL-5, was blocked by anti-Il-2-R antibodies, indicating that mIL-2 and mIL-5 use separate receptors for B cell signaling. mIL-2, as well as mIL-5, furthermore, acted as filler activities when proliferation in the presence of Ig-specific antibodies and BCGF-alpha was measured with as little as 500 B cells. In the case of mIL-5, this was also true for maturation of that few cells. Limiting dilution analyses showed that approximately 1-2% of the resting B cells matured without division, while 30-100-fold fewer cells (0.03-0.06%) proliferated and matured in response to IL-5. A single IL, therefore, is capable of inducing maturation and of stimulating mitotic cell cycle progression of normal B cells.

Autocrine growth and tumorigenicity of interleukin 2-dependent helper T cells transfected with IL-2 gene.

We introduced a mouse IL-2 cDNA expression vector into an IL-2-dependent mouse helper T cell line HT-2. Transfected cells secreted substantial amounts of IL-2, to which they themselves responded by proliferating without further requirement for exogenous IL-2. The proliferation was a direct function of the cell density and was inhibitable by antibodies against IL-2 or IL-2-R, indicating the autocrine nature of the proliferation. Those producing higher amounts of IL-2 were found to be tumorigenic when inoculated into nude mice. The latency period of tumor development correlated inversely with the level of IL-2 secreted. Tumor cells proliferated in vitro in an IL-2 autocrine fashion indistinguishable from that of the inoculated cells. We thus provide evidence that the aberrant activation of the IL-2 autocrine circuit can lead T cells to malignant transformation.

A complex of glycoproteins is associated with VpreB/lambda 5 surrogate light chain on the surface of mu heavy chain-negative early precursor B cell lines.

Monoclonal antibodies (mAbs) have been made specific for the pre-B cell-specific proteins VpreB and lambda 5 which together form the surrogate light (L) chain. mAbs specific for VpreB protein identified the 16-kD molecule associated on precursor B cell lines with lambda 5 protein as the product of the VpreB gene. Surrogate L chain was detectable even in the absence of mu heavy (H) chain on the surface of early precursor cell lines such as pro-B cell lines where all immunoglobulin (Ig) loci are in the germline configuration, as well as early pre-B cell lines where Ig H chain loci are DHJH rearranged in reading frame I or III, which does not allow the expression of a DHJHC mu protein. A complex of glycoproteins (200, 130, 105, and 65-35 kD) was identified as coprecipitated with the Vpreb/lamba 5 surrogate L chain in mu H chain-negative precursor B cell lines. The 130-kD protein was most strongly labeled with iodine and most consistently detected in noncovalent association with surrogate L chain. This protein turned out to be a N-linked glycoprotein with a 100-kD protein core and isoelectric point 5.8, indicating that it is distinct from CD43 and the BP-1/6C3 antigen. The surface deposition of the surrogate L chain in association with the newly identified glycoproteins suggests that the surrogate L chain may function as a receptor even before the association with mu H chain in early precursor B cells.

Immunoglobulin beta signaling regulates locus accessibility for ordered immunoglobulin gene rearrangements.

The antigen receptor gene rearrangement at a given locus is tightly regulated with respect to cell lineage and developmental stage by an ill-defined mechanism. To study the possible role of precursor B cell antigen receptor (pre-BCR) signaling in the regulation of the ordered immunoglobulin (Ig) gene rearrangement during B cell differentiation, a newly developed system using mu heavy (H) chain membrane exon (microm)-deficient mice was employed. In this system, the antibody-mediated cross-linking of Igbeta on developmentally arrested progenitor B (pro-B) cells mimicked pre-BCR signaling to induce early B cell differentiation in vivo. Analyses with ligation-mediated polymerase chain reaction revealed that the Igbeta cross-linking induced the redirection of Ig gene rearrangements, namely, the suppression of ongoing rearrangements at the H chain locus and the activation of rearrangements at the light (L) chain locus. Upon the cross-linking, the kappaL chain germline transcription was found to be upregulated whereas the V(H) germline transcription was promptly downregulated. Notably, this alteration of the accessibility at the H and L chain loci was detected even before the induction of cellular differentiation became detectable by the change of surface phenotype. Thus, the pre-BCR signaling through Igbeta appears to regulate the ordered Ig gene rearrangement by altering the Ig locus accessibility.

Antigen receptor engagement turns off the V(D)J recombination machinery in human tonsil B cells.

The germinal center (GC) is an anatomic compartment found in peripheral lymphoid organs, wherein B cells undergo clonal expansion, somatic mutation, switch recombination, and reactivate immunoglobulin gene V(D)J recombination. As a result of somatic mutation, some GC B cells develop higher affinity antibodies, whereas others suffer mutations that decrease affinity, and still others may become self-reactive. It has been proposed that secondary V(D)J rearrangements in GCs might rescue B cells whose receptors are damaged by somatic mutations. Here we present evidence that mature human tonsil B cells coexpress conventional light chains and recombination associated genes, and that they extinguish recombination activating gene and terminal deoxynucleotidyl transferase expression when their receptors are cross-linked. Thus, the response of the recombinase to receptor engagement in peripheral B cells is the opposite of the response in developing B cells to the same stimulus. These observations suggest that receptor revision is a mechanism for receptor diversification that is turned off when antigen receptors are cross-linked by the cognate antigen.

Ras mediates effector pathways responsible for pre-B cell survival, which is essential for the developmental progression to the late pre-B cell stage.

Ras is essential for the transition from early B cell precursors to the pro-B stage, and is considered to be involved in the signal cascade mediated by pre-B cell antigen receptors. To examine the role of p21(ras) in the late stage of B cell differentiation, we established transgenic mice (TG) expressing a dominant-inhibitory mutant of Ha-ras (Asn-17 Ha-ras) in B lineage cells at high levels after the early B cell precursor stage. Expression of p21(Asn-17) (Ha-ras) was associated with a prominent reduction in the number of late pre-B cells, but had little effect on proliferation of early pre-B cells. Inhibition of p21(ras) activity markedly reduced the life span of pre-B cells, due, at least in part, to downregulation of the expression of an antiapoptotic protein, Bcl-xL. Thus, the apparent role for p21(ras) activity in pre-B cell survival may explain the decreased numbers of late pre-B cells in Asn-17 Ha-ras TG. Consistent with this possibility, overexpression of Bcl-2 in Asn-17 Ha-ras TG reversed the reduction in the number of late pre-B cells undergoing immunoglobulin light chain gene (IgL) rearrangement and progressing to immature B cells. These results suggest that p21(ras) mediates effector pathways responsible for pre-B cell survival, which is essential for progression to the late pre-B and immature B stages.

Treatment of established renal cancer by tumor cells engineered to secrete interleukin-4.

The generation of antigen-specific antitumor immunity is the ultimate goal in cancer immunotherapy. When cells from a spontaneously arising murine renal cell tumor were engineered to secrete large doses of interleukin-4 (IL-4) locally, they were rejected in a predominantly T cell-independent manner. However, animals that rejected the IL-4-transfected tumors developed T cell-dependent systemic immunity to the parental tumor. This systemic immunity was tumor-specific and primarily mediated by CD8+ T cells. Established parental tumors could be cured by the systemic immune response generated by injection of the genetically engineered tumors. These results provide a rationale for the use of lymphokine gene-transfected tumor cells as a modality for cancer therapy.

Positive and negative selection events during B lymphopoiesis.

Early in B-cell development, large numbers of cells have to be generated, each of which expresses only one type of B-cell receptor (i.e. Ig) on its surface. This is achieved by the surface expression of a pre-B cell receptor containing a mu heavy chain/surrogate light chain which differentially provides signals for two responses of precursor B cells at this stage of development. On the one hand, it signals inhibition of further rearrangements of variable heavy chain to diverse-joining heavy chain loci to achieve allelic exclusion at the heavy-chain locus. On the other hand, it signals proliferative expansion by factors between 20 and 100. Later in B-cell development, tolerance to autoantigens must be established and maintained. Tolerance is achieved by developmental arrest and induction of secondary light-chain gene rearrangements in those IgM+ immature B cells that are reactive to autoantigens presented in the primary B-cell generating organs. Even later in development, when mature surface (s)IgM+/sIgD+ B cells encounter autoantigens presented to them in the periphery, either deletion or anergy of the autoantigen-reactive cells occurs. Anergic cells have a sIg-dependent, sIg-proximal defect in signaling and are short-lived. Anergy can be broken in vitro by polyclonal activation via ligation of CD40 in the presence of IL-4. A small part of the remaining immature B cells not reactive to autoantigens are selected to become mature, antigen-reactive sIgM+/sIgD+ B cells. Molecules which might guide such positive selection of B cells still remain to be identified.

Oncostatin M suppresses generation of lymphoid progenitors in fetal liver by inhibiting the hepatic microenvironment.

OBJECTIVE: Interaction between hematopoietic cells and stromal cells is important for regulation of hematopoiesis. Numerous soluble and membrane-bound factors directly regulating hematopoiesis have been documented, but little is known about how stromal cell activity is controlled. We previously reported that fetal hepatic cells in primary culture create the hematopoietic microenvironment and support expansion of blood cells from hematopoietic stem cells. In this study, we focused on lymphopoiesis reconstituted in our culture system and analyzed how stroma-mediated lymphopoiesis is regulated during embryonic development. MATERIALS AND METHODS: Subconfluent cultures of murine fetal hepatic cells were cocultured with hematopoietic stem cells derived from fetal liver in the presence of various cytokines. After 10 days of incubation, hematopoietic cells floating over the stromal layer were analyzed by various assays, including cell proliferation and FACS analysis. RESULTS: We found that oncostatin M, an inducer of hepatic development, strongly inhibited generation of B220(+) lymphocytic cells and colony-forming unit-interleukin-7 (CFU-IL-7) from hematopoietic stem cells in our coculture system. In contrast, oncostatin M did not directly inhibit proliferation of B cells in response to IL-7 and SCF in semisolid cultures. Analysis of antigen expression in lymphoid cells revealed that oncostatin M apparently did not arrest cells at a particular stage of B-cell development. CONCLUSIONS: The results suggest that oncostatin M inhibits lymphopoiesis by suppressing stromal activity of fetal hepatic cells to stimulate generation of CFU-IL-7 from their progenitors rather than by acting directly on lymphocytic cells.

Deficiency of a STE20/PAK family kinase LOK leads to the acceleration of LFA-1 clustering and cell adhesion of activated lymphocytes.

Lymphocyte-oriented kinase (LOK) is a member of the STE20/p21-activated kinase (PAK) family and expressed predominantly in lymphoid organs. Generation of LOK-deficient mice revealed that the leukocyte-function-associated antigen (LFA-1)/intercellular adhesion molecules (ICAM)-mediated aggregation of mitogen-stimulated T cells was greatly enhanced in the absence of LOK. Though levels of total LFA-1 and ICAMs as well as the active form of LFA-1 on T cell blasts were comparable in the presence and absence of LOK, clustering of active LFA-1 detected by binding of soluble ICAM-1 was accelerated in the absence of LOK. These results suggest that LOK is potentially involved in the regulation of LFA-1-mediated lymphocyte adhesion.

[Prosthetic application of a new measuring instrument of the dynamic periodontal function].

To investigate the principle of Periotest measurement, we compared PT-value and the duration of contact between the rod of the Periotest-Instrument and the tooth measured directly in an oral cavity. Then we applied this apparatus to the subjects with normal periodontium and the patients of prosthetic treatment. The conclusions are as follows: 1. We confirmed that PT-value was calculated from the duration of contact between the rod of the Periotest and the tooth and it showed mainly the dumping effect of the periodontium. 2. There was a close relationship between PT-value and the clinical degree of tooth mobility, especially in the degree of 0 and 1 of tooth mobility. 3. Periotest was very useful not only for the periodontal treatment but also prosthetic application.