Biomedical subjects

A B Stavitsky

Publications and source records attributed to A B Stavitsky.

At least 19 recordsLinked to original sources

PubMed2001

In vivo blockade of macrophage migration inhibitory factor prevents skin graft destruction after indirect allorecognition.

BACKGROUND: The effector mechanisms that ultimately destroy transplanted tissues are poorly understood. In particular, it is not clear how CD4+ T cells primed to donor-derived determinants expressed on recipient MHC molecules (the indirect pathway) can mediate graft destruction in the absence of cognate recognition of peptide: MHC on the graft cells themselves. Macrophage migration inhibitory factor (MIF) inhibits macrophage movement and is a proinflammatory and regulatory cytokine known to be essential for development of delayed-type hypersensitivity reactions. METHODS: To test whether MIF participates in graft destruction following indirect recognition, we studied rejection of MHC-II-deficient skin grafts placed on allogeneic SCID recipients adoptively transferred with naïve CD4+ T cells, and the recipients were treated with neutralizing anti-MIF monoclonal antibody or isotype control IgG. In this model graft rejection can only occur indirectly as the graft cells lack MHC II for recognition by the recipient CD4+ T cells. RESULTS: We found that in vivo blockade of MIF inhibited indirect CD4+ cell-mediated skin graft destruction, and markedly reduced detectable macrophages within the grafts. The neutralizing anti-MIF antibody significantly inhibited alloreactive DTH but did not prevent T cell priming or interferon-gamma release by primed T cells. CONCLUSIONS: The results strongly implicate MIF as an active participant in skin graft destruction after indirect recognition and suggest that this effect is mediated through an inhibition of macrophage migration and/or function.

Animals↗

PubMed2001

Murine schistosomiasis mansoni: coordinate cytokine regulation and differences in cellular immune responses of granuloma cells and splenocytes to endogenous and exogenous schistosome egg antigens.

To better understand the cellular immune mechanisms that regulate granulomatous inflammation to Schistosoma mansoni ova, we examined the dynamics of lymphocyte proliferation and cytokine expression by granuloma cells and splenocytes to endogenous and exogenous schistosome egg antigen (SEA) 6-19 weeks postinfection. Compared to splenocytes, granuloma cells (partially CD4+ cells) which are at the site of antigen release were highly activated by endogenous SEA and terminally differentiated as indicated by the more than 10-fold greater frequency of ex vivo interleukin (IL)-4, IL-5 and interferon (IFN)-gamma -secreting cells, greater levels of constitutive cytokine production and failure to proliferate to either endogenous or exogenous SEA. Endogenous cytokine production by granuloma cells was coordinately regulated, enhanced little by exogenous SEA, and temporally correlated with granulomatous inflammation. By contrast, CD4+ splenocytes produced comparatively little cytokine release by endogenous antigen, whereas exogenous SEA strongly induced IL-4, IL-5, IL-10 and IFN-gamma production and lymphocyte proliferation that correlated poorly with the dynamics of granulomatous inflammation. These results show that cytokine responses to endogenous SEA correlated better with granulomatous inflammation than responses to exogenous SEA. Furthermore, granuloma cells and splenocytes demonstrated strikingly different proliferative responses and dynamics of cytokine expression, suggesting that how SEA reactive lymphocytes traffic between lymphoid tissues and the granuloma is critical to a better understanding of the mechanisms of granulomatous inflammation and its modulation.

Animals↗

PubMed1998

Regulated production of type I collagen and inflammatory cytokines by peripheral blood fibrocytes.

We recently described a novel population of blood-borne cells, termed fibrocytes, that display a distinct cell surface phenotype (collagen+/CD13+/CD34+/CD45+), rapidly enter sites of tissue injury, and contribute to scar formation. To further characterize the role of these cells in vivo, we examined the expression of type I collagen and cytokine mRNAs by cells isolated from wound chambers implanted into mice. Five days after chamber implantation, CD34+ fibrocytes but not CD14+ monocytes or CD90+ T cells expressed mRNA for type I collagen. Fibrocytes purified from wound chambers also were found to express mRNA for IL-1beta, IL-10, TNF-alpha, JE/MCP, MIP-1alpha, MIP-1beta, MIP-2, PDGF-A, TGF-beta1, and M-CSF. The addition of IL-1beta (1-100 ng/ml), a critical mediator in wound healing, to fibrocytes isolated from human peripheral blood induced the secretion of chemokines (MIP-1alpha, MIP-1beta, MCP-1, IL-8, and GRO alpha), hemopoietic growth factors (IL-6, IL-10, and macrophage-CSF), and the fibrogenic cytokine TNF-alpha. By contrast, IL-1beta decreased the constitutive secretion of type I collagen as measured by ELISA. Additional evidence for a role for fibrocytes in collagen production in vivo was obtained in studies of livers obtained from Schistosoma japonicum-infected mice. Mouse fibrocytes localized to areas of granuloma formation and connective matrix deposition. We conclude that fibrocytes are an important source of cytokines and type I collagen during both the inflammatory and the repair phase of the wound healing response. Furthermore, IL-1beta may act on fibrocytes to effect a phenotypic transition between a repair/remodeling and a proinflammatory mode.

Animals↗

PubMed1989

Deficiency of interleukin-2 production upon addition of soluble egg antigen to cultures of isolated hepatic granulomas or hepatic granuloma cells from mice infected with Schistosoma japonicum.

Schistosoma japonicum-infected C57BL/6 mice show similar dynamics of hepatic granulomatous inflammation and delayed hypersensitivity elicited by soluble egg antigens (SEA) which reach peak levels at 9 weeks of infection and then spontaneously regress. In an attempt to link the level of interleukin 2 (IL-2) production to the spontaneous regression of hepatic granulomatous inflammation, the study determined the dynamics of IL-2 production by SEA-challenged isolated hepatic granulomas (HG) and cells isolated enzymatically from the HG. The production of IL-2 by SEA-stimulated HG or HG cells reached its peak when these preparations from 9-week-infected mice were stimulated and fell thereafter. Some possible mechanisms that might explain the IL-2 deficiency were examined. This deficiency is not due to the in vitro binding of IL-2 by the HG cells of infected mice and is, therefore, due rather to underproduction of IL-2. The deficiency was also not explained by reduced numbers of antigen-presenting cells (macrophages or B cells) or of L3T4+ T lymphocytes. In vitro SEA-induced IL-2 production by HG cells from acutely infected mice was suppressed consistently by Lyt-2+ T cells from the spleens and in the majority of our experiments by Lyt-2+ T cells from the HG of mice infected for 10 weeks. These findings are consistent with the main features of our working hypothesis, but it remains to be proven that in vivo deficiency of lymphokine(s) such as IL-2 is responsible for the spontaneous decrease in granulomatous inflammation and that this lymphokine deficiency is a result of suppression.

Animals↗

PubMed1988

Deficiency of interleukin-2 activity upon addition of soluble egg antigen to cultures of spleen cells from mice infected with Schistosoma japonicum.

Schistosoma japonicum-infected C57BL/6 mice show similar dynamics of hepatic granulomatous inflammation (HGI) and delayed hypersensitivity (DH) elicited by soluble egg antigens (SEA) which reach peak levels at 9 weeks of infection and then spontaneously regress. The in vitro SEA-induced proliferation of spleen cells (SC) from infected animals attained its high point and then declined when SC from 5-week-infected mice were used. The present study determined the dynamics of interleukin-2 (IL-2) production by SEA-challenged SC from infected mice in an attempt to link the level of IL-2 production to the spontaneous regression of the aforementioned T-cell-mediated immune responses. The production of IL-2 by SEA-stimulated SC reached its peak when cells from 7-week-infected mice were challenged at least 2 weeks after the peak of the proliferative response, but declined at about the same time as the HGI and DH responses. Therefore, the decline in IL-2 activity cannot alone explain the diminished proliferative response but could account for the reduction in HGI and DH in vivo. Some possible mechanisms that might explain the IL-2 deficiency were examined. This deficiency is not due to the in vitro binding of IL-2 by the SC of infected mice and is, therefore, likely to be due to underproduction of IL-2. Nor is the deficiency explained by reduced numbers of antigen-presenting cells (macrophages and B cells) or of L3T4+ T lymphocytes or by suppression of IL-2 production by macrophages or macrophage products such as prostaglandins. However, suppression of IL-2 production was observed consistently upon coculture of SC from acutely infected mice with SC from mice infected for 10 weeks. The cells which suppress appear to be Lyt2+ T cells. The data are consistent with the hypothesis that suppressor T cells inhibit the production of IL-2 and perhaps of other cytokines or lymphokines and that this suppression explains the spontaneous down-regulation of HGI which occurs during schistosomiasis japonica.

Animals↗

PubMed1986

Mechanisms of in vivo modulation of granulomatous inflammation in murine schistosomiasis japonicum.

In schistosomiasis japonicum, the major pathologic lesion is the granulomatous inflammation that occurs around parasite eggs trapped in the liver. The size of these granulomas and their major sequela, a rise in portal pressure, both peak between 8 and 10 weeks after infection and then spontaneously decrease. We have shown that the adoptive transfer of the serum, but not lymphoid cells, of 30-week-infected mice caused decreases in both the size of the hepatic granulomas and the portal pressure of acutely infected recipient mice. The present study examines the role of both humoral (serum) and cellular immune mechanisms of modulation throughout the course of murine infection. Pools of serum (0.3 ml), spleen cells (5 X 10(7)), or splenic T cells (2 X 10(7)) from mice infected for 10, 20, and 30 weeks were adoptively transferred into mice at 4 and 5 weeks of infection. One week later (6 weeks postinfection), the portal pressure and size of hepatic granulomas in all recipient mice were determined. The 10-week-infected mouse serum occasionally lowered these values, but serum from 20- and 30-week-infected animals was consistently suppressive. The active component of 30-week-infected mouse serum coeluted with immunoglobulin G1. In contrast, 10-week-infected spleen cells or T cells consistently lowered portal pressure and granulomatous inflammation, but 20- and 30-week spleen cells did not. The phenotype of these suppressive T cells was Lyt-1-2+. These in vivo observations confirm earlier in vitro studies on cellular and humoral immune modulation of egg antigen-induced spleen cell blastogenesis. The current study demonstrates that both cellular and humoral regulation of granulomatous inflammation occur in murine schistosomiasis japonicum but with different kinetics: cellular mechanisms are maximal early (10 weeks) while humoral mechanisms predominate late during the chronic stage of infection (20 and 30 weeks).

Animals↗

PubMed1986

Inhibition of immediate and Arthus responses to schistosome egg antigens by T cells from Schistosoma japonicum-infected mice.

Schistosoma japonicum-infected mice develop hepatic granulomas, immediate hypersensitivity (IH), and delayed hypersensitivity (DH) to soluble egg antigens (SEA) released by parasite eggs trapped in liver sinusoids. All of these responses spontaneously regress after 7 to 9 weeks of infection. This study aimed to develop an in vivo system for the further dissection of cellular and humoral immune responses to SEA. C57BL/6 mice immunized subcutaneously with SEA in complete Freund adjuvant developed IH, an Arthus reaction, and DH to this antigen 5 to 9 days later. IH and the Arthus reaction, but not DH, were markedly inhibited if, 1 day before injection of SEA in complete Freund adjuvant, the mice were injected intravenously with purified T cells from the spleens of mice infected for at least 9 weeks. This in vivo model system can be used to study various aspects of cellular and humoral immune responses to SEA and their modulation. These results raise questions about the role of antibodies in the pathogenesis of granulomatous inflammation and about the mechanisms of its cellular regulation in infections with S. japonicum.

Animals↗

PubMed1985

Mitogen-induced phosphorylation of cytosolic proteins in rabbit T- and B-lymphocytes.

The addition of anti-immunoglobulin (anti-Ig) to purified rabbit B-cells or concanavalin A (Con A) to purified rabbit T-cells within minutes resulted in the phosphorylation of a number of cytosolic proteins. Two-dimensional (2-D) electrophoresis and autoradiography of 32P-labeled cell sonicates was used to identify proteins whose phosphorylation was enhanced by these mitogens. Two proteins, pp58 and pp90, were phosphorylated 1.5 min after addition of anti-Ig to B-cells. Four other proteins, pp60, pp65, pp67 and pp95, were phosphorylated at later times. Three of these proteins were also phosphorylated after addition of Con A to purified T-cells. These phosphoproteins do not correspond to any previously described cytoplasmic proteins. Although all of these phosphoproteins were present in the cytosolic fraction, pp58 may be associated with the cytoskeleton. Protein pp58 is also distinguished from the rest by its absence from 2-D gels run under non-reducing conditions. Treatment of the B-cells with F(ab')2 fragments of anti-Ig stimulated phosphorylation but Fab' fragments did not--indicating that receptor cross-linking is required to induce phosphorylation. Both pp58 and pp90 contained phosphoserine, but neither phosphothreonine nor phosphotyrosine. Quantitatively the 32P-labeling of pp58 was 2.7-fold over background at 10 min after anti-Ig addition. The identification of these phosphoproteins, which may play a role in activational cascades or in cytoskeletal rearrangements, hopefully will help to clarify the interrelationships between cyclic nucleotide dependent and independent kinases in lymphocyte activation.

Amino Acids↗

PubMed1985

Regulation of egg antigen-induced in vitro proliferative response by splenic suppressor T cells in murine Schistosoma japonicum infection.

Beginning about 5 weeks after infection, C57BL/6J mice infected with Schistosoma japonicum developed granulomas around parasite eggs trapped in the liver. These granulomas attained peak size about 9 weeks after infection and then spontaneously regressed. This regression was also induced by the injection of serum immunoglobulin G1 but not lymphoid cells from chronically infected mice, but it was conceivable that lymphoid cells from mice infected for 10 weeks could also induce regression. We investigated the possibility of cellular suppression of egg antigen-induced immune responses by coculturing spleen cells from 5- to 6-week-infected mice with spleen cells from mice infected for 10 weeks or longer. Mitomycin C-resistant Thy 1.2+, Lyt 2.2+ splenic T cells from mice infected for 10 to 25 weeks consistently suppressed the egg antigen-stimulated proliferation of spleen cells from 5- to 6-week-infected mice. Suppression was dependent upon specific antigen and optimal concentrations of egg antigen and T suppressor cells. Once induced, the suppressor cells were nonspecific. Cultured T cells from uninfected mice also occasionally suppressed the acute spleen cell proliferative response, but these cells were mitomycin C sensitive. These in vitro observations suggest that granulomatous inflammation in vivo may also be down regulated by suppressor T cells and that these cells may also be implicated in the nonspecific depression of cellular and humoral responses to antigens observed during the course of this infection.

Animals↗

PubMed1984

Effects of trifluoperazine, a calmodulin antagonist, on rabbit T- and B-cell responses to mitogens and antigen.

Trifluoperazine (TFP), an inhibitor of the calcium-binding protein, calmodulin (CaM), was used to assess the role of calmodulin in the responses of rabbit lymphoid cells to stimulation with mitogen and antigen. After binding goat anti-rabbit Fab antibody, rabbit B cells lose their surface immunoglobulin (Ig) through endocytosis and then reexpress this protein during the next 24 hr. This reexpression was markedly inhibited by TFP. The brief and early addition of TFP markedly inhibited the increased [3H]thymidine (Tdr) uptake by rabbit T cells treated with concanavalin A and B cells exposed to anti-Fab. TFP greatly inhibited the induction by keyhole limpet hemocyanin (KLH) of the in vitro syntheses of antibody, Ig, and protein by KLH-primed lymph node cells (LNC). The earlier the TFP the greater was the inhibition of induction of these syntheses. However, once induced, synthesis and secretion of antibody were not inhibited by TFP. In striking contrast to the inhibition by TFP of the mitogenic and antigenic responses of lymphoid cells was the lack of effect of this drug on resting lymphocytes. Since TFP was not cytotoxic for either resting or mitogen- or antigen-stimulated LNC, it is highly unlikely that the observed inhibitory effects of this drug were due to its cytotoxicity. We postulate that an early signal for the activation of LNC proliferation, differentiation, and the syntheses of antibody, Ig, and protein involves a calcium-CaM-mediated reaction. Based on this work and that of others, the calcium-CaM complex may mediate an interaction between the ligand-occupied surface receptor and the cytoskeleton.

Animals↗

PubMed1984

Depressed in vitro and in vivo antibody response and adoptive transfer of delayed hypersensitivity to myoglobin with spleen cells of mice chronically infected with Schistosoma japonicum and injected with myoglobin.

Spleen cells from C57BL/6J mice infected for 21 weeks with Schistosoma japonicum did not show an in vitro secondary antibody response upon challenge with sperm whale myoglobin. Mice infected for 13 weeks showed almost no in vivo secondary antibody response to this antigen. Spleen cells from mice infected for 12 to 21 weeks did not adoptively transfer delayed hypersensitivity to this antigen.

Animals↗

PubMed1984

Spontaneous and egg antigen-induced syntheses of immunoglobulin and antibody by spleen cells and hepatic granulomas of mice infected with Schistosoma japonicum.

In the absence of egg antigen (SEA), spleen cells from C57BL/6 mice infected for 22 weeks with Schistosoma japonicum were spontaneously induced in vitro to synthesize total immunoglobulin and antibody to SEA. Hepatic granulomas from mice infected for 12 weeks, but not for 22 weeks, also showed spontaneous syntheses of total immunoglobulin and antibody to SEA, but these syntheses were not enhanced upon the addition of SEA. Total immunoglobulin production was enhanced when SEA was added to spleen cells from mice infected for 4 to 7 weeks but not at any other time point.

Animals↗

PubMed1983

Anti-immunoglobulin-induced proliferative response of rabbit lymphocytes in a serum-free medium.

The aim of this study was to determine if rabbit lymphocytes were activated with a specific ligand, anti-immunoglobulin (anti-Ig) in a well-defined serum-free medium. A modified medium, composed of Neuman-Tytell (NT) basal medium supplemented with BSA, transferrin (Tf), and fatty acids (FA), was found to support a vigorous anti-Ig-induced proliferative response of rabbit lymphocytes. The optimal concentrations of BSA, Tf and FA supplements were determined for the mitogen-induced response. The mitogenesis was enhanced by addition of 2-mercaptoethanol. The proliferation could be maintained for 10 days provided cells received fresh medium and mitogen on day 5. The presence of anti-Ig throughout the culture period is required for this extended proliferation. The response did not require the Fc portion of the anti-Ig and was blocked by soluble rabbit F(ab')2 fragments. The anti-Ig-activated blasts lacked a T cell surface marker and about half of them re-expressed sIg when anti-Ig was washed out (assayed 24 h later). The viability of the mitogen-induced cells on day 5 was above 55%, whereas the viability of the cells without mitogen was 36%. The supplemented NT medium could also support Con A-induced mitogenesis of rabbit lymphocytes. Additionally, Con A- and LPS-stimulated murine lymphocytes showed considerable proliferation for up to 5 days in the supplemented NT medium.

Animals↗

PubMed1982