Spleen Cell Suspensions Research Articles

B cell and immunoglobulin heterogeneity in carp ( Cyprinus carpio L); An immuno(cyto)chemical study

B cell and immunoglobulin (Ig) heterogeneity was demonstrated in carp, Cyprinus carpio L., using two monoclonal antibodies (MAbs; WC14, WCI12) produced against carp serum Ig. Immunochemical results showed that both WCI4 and WCI12 react with a protein determinant on the heavy chain of Ig (relative molecular mass ~70,000). Immunofluorescence microscopic and flow cytometric analyses of lymphoid cells suggest three distinct subpopulations of B cells and plasma cells: WCI4 +12 − cells, WCI4 −12 + cells, and WCI4 +12 + cells. WCI4 −12 + and WCI4 +12 + anti-DNP antibody-secreting cells were also demonstrated with the ELISPOT assay in pronephros and spleen cell suspensions from primary immunised carp. Affinity chromatography of carp serum and sequential immunoprecipitation of 125I-labelled peripheral blood leucocyte (PBL) membrane proteins only indicated the presence of two antigenically different Ig molecules i.e., WCI4 −12 + and WCI4 +2 + molecules. WCI4 +12- molecules could not be detected by affinity chromatography or immunoprecipitation. During ontogeny, a shift in percentages of WCI4 +12 − and WCI4 −12 + cells was found in the spleen and the pronephros. In these organs, WCI4 +12 − cells formed the majority of B cells at 2 weeks of age, but the percentages of this cell type decreased during ontogeny. On the other hand, the percentages of WCI4 −12 + cells increased during development, and these cells became the major population of B cells from 13 weeks Address correspondence to Dr. J.H.W.M. Rombout. onward. The proportion of WCI4 +12 + cells remained almost constant during ontogeny. The distribution of B cell subpopulations in blood was more or less stable at all ages. The functional significance of Ig heterogeneity in fish and in particular carp is discussed.

Immunoregulatory properties of hexapeptide isolated from porcine bone marrow cell culture

Myelopeptide 1 (MP-1) is hexapeptide originally isolated from porcine bone marrow cell culture. It was synthesized and its immunoregulatory properties were studied. MP-1 caused a 1.5–2-fold dose-dependent increase of antibody production in the culture of mouse immune lymph node cells. It abolished Con A induction of T suppressors in the suspension of mouse spleen cells and counteracted the inhibitory effect of T suppressors on antibody production. The inoculation of MP-1 (1·10 −9 g/mouse) to mice two weeks after their γ-irradiation (2 Gy) resulted in an increase of antibody production up to 80.2 ± 15.5% as compared to that in the irradiated control 37.6 ± 12.0%. Immunofluorescent analysis revealed the specific binding of MP-1 with receptors on the target cells in the suspension of mouse spleen cells. It is supposed that MP-1 participates in the immunoregulatory processes in the living organism.

Influence of organophosphorus compounds on different cellular immune functions in vitro

The effects of two organophosphorus compounds (OP) triphenyl phosphate (TPP) and triphenylphosphine oxide (TPPO) on different immune functions in vitro were investigated using an economical multiple endpoint approach. The test battery was designed as follows: immunocompetent cells (peritoneal cells and splenocytes) were isolated from female C57B1 mice and treated in vitro for 1 hr with the test article. Then the cells were washed and assessed for the following immune functions: Fc-receptor-dependent phagocytosis and lipopolysaccharide-induced release of a cytolytic protein (tumour necrosis factor, TNF) of thioglycollate-elicited peritoneal macrophages; natural killer (NK) cell activity, blastogenesis (T and B lymphocytes), and antibody synthesis (B lymphocytes) of spleen-cell suspensions. As an additional parameter the survival of the cells was determined routinely after treatment during all assays. No substantial effect on macrophage phagocytotic activity was observed after TPP or TPPO treatment. TPP led to a concentration-dependent suppression of macrophage TNF activity as well as NK activity of spleen cells. In addition, a slight reduction of B-lymphocyte antibody synthesis was obtained. TPPO treatment revealed a modulation of TNF activity of macrophages in a complex, non-concentration-related manner. A concentration-related suppression of spleen cell NK activity was observed after TPPO treatment. In summary, TPP and TPPO were found to be immunomodulating agents eliciting adverse effects predominantly towards cells of the innate immunity. The functions of T and B lymphocytes, referred to as adaptive immunity, were not substantially impaired. Our results indicate that the in vitro test battery described may be a suitable tool for the screening of OP-mediating immunotoxicity.

Left ventricular endocardial proliferation in chickens.

Left ventricular endocardial proliferation in chickens.

Transplantation of spleen cells in patients with hemophilia A

It has been reported that coagulation factor VIII (F. VIII) is produced in the spleen and other organs. Transplantation of splenic whole organ and spleen cells may, therefore, be used to treat patients with hemophilia A. The donor spleen from brain-dead donors was used to prepare spleen cell suspension for transplantation. Twenty-two spleen cell transplantations were performed on 20 patients suffering from severe hemophilia A at our institutes. Two of them underwent a second infusion of spleen cells since there was no increase in plasma F. VIII activity after the first transplantation. All but two patients showed a marked clinical improvement. Increased plasma F. VIII activity was observed in 18 of 20 cases. The peak plasma F. VIII activity in these recipients rose to 10%-15% posttransplantation in 14 cases and to over 15% in 4 cases from pretransplant levels of 0%-3%. Generally, the elevation of plasma F. VIII activity could be detected 4-7 days following transplantation of spleen cells and this lasted from 22 to 58 weeks. Four patients whose peak plasma F. VIII activity was greater than 15% experienced an uneventful course after transplantation. The patients with plasma F. VIII activity over 10% showed less frequent bleeding and prolonged intervals between bleed as well as improvement in hemophilic arthrosis. Two patients who had interval hematuria before transplantation did not have any relapse for up to 2 years after infusion of the spleen cells. These results indicate that spleen cell transplantation may be a promising method for the management of patients with hemophilia A.

CD4pos, NK1.1pos T cells promptly produce interleukin 4 in response to in vivo challenge with anti-CD3.

Injection of anti-CD3 antibodies causes prompt expression of interleukin (IL)-4, IL-2, and interferon gamma (IFN-gamma) mRNA among spleen cells. The optimal dose of anti-CD3 for such induction was 1.33 microgram/animal; lymphokine mRNA was first observed at 30 min, peaked at 90 min, and was undetectable (for IL-4) or had declined markedly by 4 h. Cells harvested from spleens of mice injected with anti-CD3 90 min earlier secreted IL-4, IL-2, and IFN-gamma without further stimulation. By contrast, in vitro stimulation with anti-CD3 of spleen cell suspensions or splenic fragments from noninjected donors failed to cause prompt production of IL-4 and, even after 24 h of stimulation, the amount of IL-4 produced in such cells was substantially less than that secreted within 1 h by spleen cell suspensions or splenic fragments from mice injected with anti-CD3 90 min earlier. Production of IL-4 by spleen cells from anti-CD3-injected mice was not inhibited by pretreatment with anti-IL-4 antibody or with IFN-gamma or tumor growth factor beta nor enhanced by treatment with IL-4. By contrast, CTLA-4 immunoglobulin (Ig) treatment clearly diminished IL-4 production in response to in vivo anti-CD3, indicating that cellular interactions involving CD28 (or related molecules) were important in stimulation. Cell sorting analysis indicated that the cells that produced IL-4 in response to in vivo injection of anti-CD3 were highly enriched in CD4pos cells with the phenotype leukocyte cell adhesion molecule-1 (LECAM-1)dull, CD44bright, CD45RBdull, NK1.1pos. Indeed, the small population of CD4pos, NK1.1pos cells had the great majority of the IL-4-producing activity of this population. Injection with Staphylococcal enterotoxin B also caused prompt induction of IL-4 mRNA; the cells that were principally responsible for production also had the phenotype of CD4pos, NK1.1pos. These results suggest that possibility that this rare population of T cells may be capable of secreting IL-4 at the outset of immune responses and thus may act to regulate the pattern of priming of naive T cells, by providing a source of IL-4 to favor the development of T cell helper 2-like IL-4-producing cells.

Ionizing radiation and autoimmunity. Induction of autoimmune disease in mice by high dose fractionated total lymphoid irradiation and its prevention by inoculating normal T cells.

Ionizing radiation can functionally alter the immune system and break self-tolerance. High dose (42.5 Gy), fractionated (2.5 Gy 17 times) total lymphoid irradiation (TLI) on mice caused various organ-specific autoimmune diseases, such as gastritis, thyroiditis, and orchitis, depending on the radiation dosages, the extent of lymphoid irradiation, and the genetic background of the mouse strains. Radiation-induced tissue damage is not the primary cause of the autoimmune disease because irradiation of the target organs alone failed to elicit the autoimmunity and shielding of the organs from irradiation was unable to prevent it. In contrast, irradiation of both the thymus and the peripheral lymphoid organs/tissues was required for efficient induction of autoimmune disease by TLI. TLI eliminated the majority of mature thymocytes and the peripheral T cells for 1 mo, and inoculation of spleen cell, thymocyte, or bone marrow cell suspensions (prepared from syngeneic nonirradiated mice) within 2 wk after TLI effectively prevented the autoimmune development. Depletion of T cells from the inocula abrogated the preventive activity. CD4+ T cells mediated the autoimmune prevention but CD8+ T cells did not. CD4+ T cells also appeared to mediate the TLI-induced autoimmune disease because CD4+ T cells from disease-bearing TLI mice adoptively transferred the autoimmune disease to syngeneic naive mice. Taken together, these results indicate that high dose, fractionated ionizing radiation on the lymphoid organs/tissues can cause autoimmune disease by affecting the T cell immune system, rather than the target self-Ags, presumably by altering T cell-dependent control of self-reactive T cells.

Immunomodulating Actions of RNA and Nucleotides on Murine LymphocytesIn Vitro

Abstract We have shown previously that yeast RNA significantly enhances in vitro antibody (Ab) production to sheep red blood cells (SRBC) in mice which can be partially reproduced by certain mononucleotides. In this study, mechanisms of this enhancing action by RNA and nucleotides were further explored in C57B/6 (B6) mice. Yeast RNA and certain mononucleotides augmented in vitro Ab production to SRBC and TNP-KLH (T dependent antigens) but not to TNP-LPS (a T independent antigen) and this action of RNA was abolished if T cells were depleted from spleen cell suspensions. RNA was most effective when supplemented on the first day of the culture for Ag priming. When RNA was supplemented after day 3 of the culture of Ag priming, no significant augmentation was observed. When spleen cells were cultured in the RNA supplemented medium, a frequency of L3T4+, CD5+, and Thy-1+ T helper cells increased significantly compared to controls cultured without RNA. However, yeast whole RNA did not appear to enhance IL-2 or I...

Kinetic analysis of antigen-specific immune responses in resistant and susceptible mice during infection with Trypanosoma cruzi.

The Tulahuén strain of Trypanosoma cruzi has been shown previously to cause higher parasitemias and greater mortality in BALB/c mice compared with C57BL6/J mice. The goal of our study was to determine whether different cytokine responses to parasite Ag during T. cruzi infection correlate with the susceptible and resistant phenotypes identified in these mice. At several time points after initial infection with insect-derived metacyclic trypomastigotes, lymph node and spleen cell suspensions were prepared from animals of each mouse strain. These lymphocyte suspensions were stimulated with Ag prepared from cultured parasites and the production of IFN-gamma, IL-4, IL-2, and IL-5 was measured. Lymphocytes from C57BL6/J mice produced 10-fold more IFN-gamma than BALB/c lymphocytes. However, this enhanced response occurred only for a limited time preceding peak parasitemias. Ag-induced secretion of IL-4 from BALB/c lymphocytes was detectable by 2 wk of infection and increased during the 2nd and 3rd mo of infection. Most C57BL6/J culture supernatants did not contain measurable levels of IL-4. Lymphocytes from both murine strains produced levels of IL-2 and IL-5 indistinguishable from uninfected controls. These results indicate that increased numbers or potency of lymphocytes that produce Ag-specific IFN-gamma responses are present in resistant mice during T. cruzi infection. This phenomenon may be responsible for the lower parasitemias seen in C57BL6/J mice. However, even these relatively resistant mice become chronically infected with T. cruzi, and spleen cells from infected mice can suppress IFN-gamma induced by heterologous Ag. Our data suggest that IL-4 production is a marker for the T. cruzi susceptible phenotype. Differential production of IL-2 or IL-5 was not found, suggesting that these cytokines are not important factors in T. cruzi resistance or susceptibility.

The essentiality of folate for the maintenance of deoxynucleotide precursor pools, DNA synthesis, and cell cycle progression in PHA-stimulated lymphocytes.

The fidelity and progression of DNA synthesis is critically dependent on the correct balance and availability of the deoxynucleoside triphosphate (dNTP) precursors for the polymerases involved in DNA replication and repair. Because folate-derived one-carbon groups are essential for the de novo synthesis of both purines and pyrimidines, the purpose of this study was to determine the effect of folate deprivation on deoxynucleotide pool levels and cell cycle progression. Primary cultures of phytohemagglutin (PHA)-stimulated splenocytes were used as the cellular model. T-cells and macrophages were purified from spleen cell suspensions obtained from F344 rats and recombined in culture. The cells were harvested after a 66-hr incubation with PHA and analyzed for nucleotide levels by reverse-phase HPLC with diode array detection. The proportion of cells in the different phases of the cell cycle was determined by bivariate flow cytometric measurement of bromodeoxyuridine (BrdU) incorporation and DNA content (propidium iodide staining). PHA-stimulated T-cells cultured in medium lacking folate and methionine manifested significant decreases in the deoxynucleotides dCTP, dTMP, dGTP, and dATP relative to cells cultured in complete medium. The reduction in dNTP pools was associated with a decrease in the corresponding ribonucleotide pools. Flow cytometric analysis revealed a 2-fold increase in S and G2/mitosis (G2/M) DNA content in PHA-stimulated cells cultured in the medium lacking folate and methionine, which suggests a delay in cell cycle progression. These alterations in DNA content were accompanied by a 5-fold decrease in BrdU incorporation relative to PHA-stimulated cells cultured in complete medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of burn injury on class-specific B-cell population and immunoglobulin synthesis in mice.

Mice of the C57BL/6 strain were studied to investigate the effects of a 20% total body surface area full-thickness burn on class-specific immunoglobulin synthesis. Five days after injury single cell suspensions of spleen and mesenteric lymph node cells were made. The number of class-specific immunoglobulin-bearing cells were counted by flow cytometry using Texas-red-labelled antibody to class-specific mouse immunoglobulin. The remaining cells were cultured with lipopolysaccharide for 4 days. The supernatant was tested for class-specific immunoglobulin by enzyme-linked immunosorbent assay (ELISA). There was no change in the number of class-specific IgG and IgA lymphocytes, but there was a significant increase in IgM lymphocytes. Synthesis of immunoglobulin by 10(5) lymphocytes was significantly increased in IgG and IgA cells, but decreased in IgM cells. Similar results were shown in spleen and mesenteric lymph node cells. Because the IgM response was much greater than others in the number of cells and immunoglobulin synthesis, we conclude that the decrease in responsiveness of IgM may contribute significantly to increased host susceptibility to infection after burn.

Direct effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on responses to lipopolysaccharide (LPS) by isolated murine B-cells

Previous results from this laboratory have indicated that the B-cell is the primary cell target responsible for the suppression of humoral immunity by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). While other laboratories have confirmed that the B-cell is affected, there is not a clear understanding of TCDD's relative effects on B-cell proliferation and differentiation. In the present study, we isolated B-cells from the whole spleen cell suspensions from female B6C3F1 mice and further separated them according to density on a percoll density step gradient. Cell cycle analysis by propidium iodide indicated that both high (i.e., 1.092–1.079 density interface) and low (i.e., 1.079–1.070 density interface) density B-cells were predominantly cells in the G0/G1 phase of the cell cycle. Based on acridine orange staining, low-density B-cells exhibited slightly higher RNA levels than high-density B-cells indicating they are an “activated” population of cells, probably somewhere in G1A. Confirmation of these results was the observation that the high density, small, resting B-cells had negligible background proliferation and immunoglobulin secretion, while the low density, larger, activated B-cells had marked background proliferative and antibody responses. Direct addition of TCDD (0.3–30.0 nM) produced a significant, dose-related and comparable suppression of both parameters in the low density B-cells. Similar results were obtained when low density B-cells were stimulated with LPS and exposed to TCDD. In contrast, neither the proliferation nor the antibody response by high density B-cells stimulated with LPS were affected by TCDD. These findings demonstrate that the low density splenic B-cells are targets in suppression of antibody responses by TCDD, and that both proliferation and differentiation are coordinately affected.

Interleukin‐6 production during chronic experimental infection

The appearance of interleukin-6 (IL-6) in serum of mice was monitored during the course of chronic infection with either Brucella abortus vaccine strain 19 or a virulent Mycobacterium avium Complex (MAC) isolate. Serum IL-6 during brucella infection was higher than during infection with MAC, despite similar numbers of bacteria. Furthermore, IL-6 titres decreased after the peak of infection, falling to baseline levels before these chronic infections were eradicated. The ability of peritoneal cells or spleen cell suspensions to produce IL-6 under either specific or non-specific stimulus was greatly enhanced by infection. While production of IL-6 by these cultures was apparently mostly independent of T cells, T cells from infected mice could produce an IL-6 response. Thus CD4+ T lymphocytes prepared from mice which had recovered from B. abortus infection, cultured with antigen and antigen presenting cells, resulted in IL-6 production, which was not observed in similarly cultured CD8+ T cells, indicating a role for T cells.

Enhancement of interleukin-4 production by pertussis toxin

Pertussis toxin (PT), a protein toxin of Bordetella pertussis, has many biological activities, including potent adjuvant capacity and the ability to up-regulate immunoglobulin E (IgE) production. Interleukin-4 (IL-4) is a cytokine which is essential for the IgE response. Accordingly, we examined the effect of PT on IL-4 production. Spleen and lymph node cell suspensions were prepared from immunized mice and cultured with antigen or polyclonal stimuli in vitro. IL-4 secretion was assessed by bioassay, and IL-4 mRNA expression was assessed by reverse transcription and polymerase chain reaction. Significantly larger amounts of IL-4 protein and mRNA were produced in vitro by cells from mice given PT at the time of immunization than by cells from mice given antigen alone, PT alone, or the combination of antigen with cyclophosphamide. Total and antigen-specific serum IgE levels were significantly elevated in immunized mice given PT, compared with the other groups. Thus, there was a relationship between serum IgE and IL-4 production. The administration of a single dose of an anti-IL-4 monoclonal antibody in vivo, at the time of immunization and treatment with PT, abolished the development of the IgE response. These results indicate that PT is a potent stimulus for the production of IL-4, which is required for the adjuvant effect of PT on IgE formation.

Immunotoxicity screening in vitro using an economical multiple endpoint approach

An economical multiple endpoint in vitro test battery has been developed for screening chemically induced immune dysfunction. Bearing in mind the complexity of the immune system, different types of immunocompetent cells were used. Cofactor-fortified liver homogenate obtained from rats pretreated with Aroclor (S-9 mix) was employed as an in vitro metabolizing system. The following principal screening design was applied. Immunocompetent cells (peritoneal cells and splenocytes) obtained from female C57B 1 mice were treated in vitro for 1 hr. For metabolic activation, chemicals were pretreated with S-9 mix for 2 hr. After the incubation period the cells were washed and different immune function assays (antibody-dependent phagocytosis and lipopolysaccharide-induced release of tumour necrosis factor of thioglycollate-elicited peritoneal macrophages; natural killer cell activity, T- and B-cell blastogenesis, and B-cell antibody synthesis of spleen cell suspensions) were performed. For economy the different spleen cell functions were tested in parallel with aliquots of cells derived from the same chemically treated culture. As an additional parameter the survival of the cells was determined routinely after treatment during all assays. Different chemicals (e.g. tributyltinoxide, 7,12-dimethylbenzanthracene, lead acetate, cyclophosphamide, dexamethasone) were assessed using this system. The results indicate that the in vitro test battery described is a suitable tool for immunotoxicity screening.

A simple method for negative and positive selection of murine and human IgM-bearing lymphocytes based on the use of antibody-coated silica microparticles

The use of octadecyl silica microparticles is proposed as an alternative method for negative and positive selection of IgM-bearing lymphocytes. SiC18 microparticles coated with affinity purified IgG anti-IgM were evaluated in their efficiency to deplete IgM-bearing cells. 6 mg of SiC18-IgG depleted an average of 97% IgM-bearing cells from a murine spleen cell suspension and of 84% IgM-bearing cells from human spleen cells. The viability of the selected cells was not affected by this procedure. We also analyzed the ability of whole serum to release IgM-bearing cells from the complex SiC18-target cell. The IgM releasing efficiency was 98%, with a resulting viability of 85%. These results indicate that SiC18 microparticles, saturated with specific antibodies, may be used as an alternative method for depletion or purification of cells bearing the corresponding antigen, from complex cell suspensions. The method is simple, efficient and inexpensive, representing an interesting alternative to the immunomagnetic selection.

Studies of immunomodulating actions of carotenoids. II. Astaxanthin enhances in vitro antibody production to T-dependent antigens without facilitating polyclonal B-cell activation.

Previously we have shown that astaxanthin, a carotenoid without provitamin A activity, enhances in vitro antibody (Ab) production to sheep red blood cells in normal B6 mice. In this study, we further attempted to examine the mechanisms of this enhancing action of carotenoids on specific Ab production in vitro in relation to different antigen (Ag) stimuli, cytokine production, and T- and B-cell interactions in both normal and autoimmune strains of mice. When the actions of carotenoids were tested in normal strains of mice, we found that astaxanthin enhanced in vitro Ab production to T cell-dependent Ag, but not to T-independent Ag, and did not augment total immunoglobulin production. Astaxanthin exerted maximum enhancing actions when it was present at the initial period of Ag priming. This action of astaxanthin was abolished when T cells were depleted from spleen cell suspensions and appeared to require direct interactions between T and B cells. The results also indicated that carotenoids may modulate the production of interferon-tau in this assay system. When the actions of carotenoids were tested in autoimmune-prone MRL and NZB mice, the enhancing action of astaxanthin on in vitro Ab production was less significant. Furthermore, carotenoids did not potentiate or augment spontaneous Ab and immunoglobulin production by spleen cells in these strains. Taken together, carotenoids without provitamin A activity may be able to augment in vitro specific Ab production to T cell-dependent Ag partly through affecting the initial stage of Ag presentation without facilitating polyclonal B-cell activation or autoantibody production.

Mouse splenic macrophage cell lines with different antigen-presenting activities for CD4 + helper T cell subsets and allogeneic CD8 + T cells

A panel of seven mouse splenic macrophage cell lines, derived from cloned progenitors, was compared for their ability to present antigen to Th 1 or Th 2 helper T cell lines and hybridomas, as well as to naive T cells, and to provide accessory cell function for the synthesis of antibody from primed B cells. One of the cell lines expressed MHC class II molecules and was the only line with constitutive antigen-presenting activity for Th 1 cells. It may represent a subset of splenic macrophages responsible for the activation of naive Th 1 helper cells in situ. The remaining six cell lines responded to INF-γ by up-regulating their class II expression and acquiring Th 1 antigenpresenting activity. They may represent cells which, in situ, lack constitutive antigen-presenting activity but are promoted to presenting status by Th 1-derived INF-γ. Five of the cell lines provided accessory cell function to Th 2 cells, as indicated by antibody synthesis in suspensions of spleen cells from primed mice depleted of their antigen-presenting cells. One of the cell lines lacking accessory cell activity had constitutive antigen-presenting activity for Th 1 cells. This reciprocal expression of antigen-presenting activity supports the idea that Th 1 and Th 2 helper cells are activated by different antigen-presenting cells. Finally, the cell lines differed in their ability to constitutively induce an allogeneic response; a response that was limited to CD8 + T cells occurred in a CD4 + helper cell-independent manner and was unaffected by the addition of INF-γ. The alloantigenpresenting macrophage cell lines also possessed the most efficient accessory cell activity for antibody synthesis. These cell lines, which represent a spectrum of antigen-presenting activities in the spleen afford models for defining the roles of macrophages in the induction of immune responses and for resolving issues concerning their development.

Evidence that mannose recognition by splenic sinusoidal cells plays a role in the splenic entry of lymphocytes.

Previous studies demonstrated that mannan is a potent inhibitor of splenic entry of lymphocytes and mediates its inhibitory effect at an unidentified site in the spleen rather than acting directly on lymphocytes. This report describes the in vivo site of action of mannan. In vivo localization studies with fluoresceinated preparations of mannan (Fl-mannan) and a mannose-6-phosphate-containing yeast phosphomannan monoester core from P. holstii exopolysaccharide (Fl-PPME) demonstrated that the polysaccharide specifically localize in the splenic marginal sinuses in cells with a dendritic morphology termed splenic sinusoidal cells (SSC). Uptake of the polysaccharides by SSC was mediated by a mannan-specific receptor which was saturable and of high avidity. Several lines of evidence suggested that mannan uptake by SSC inhibited splenic entry of lymphocytes. First, the ability of SSC to bind Fl-mannan and Fl-PPME closely paralleled the ability of these polysaccharides to inhibit splenic entry of lymphocytes. In fact, doses of mannan and PPME which would saturate SSC mannan receptors completely blocked splenic entry of lymphocytes. Second, SSC are situated at the initial entry point of lymphocytes into spleen and passage of lymphocytes through the SSC region of spleen was profoundly inhibited by mannan. Finally, direct evidence for adhesion between lymphocytes and SSC was obtained with spleen cell suspensions where clustering between Fl-mannan labeled SSC and lymphocytes was observed. Collectively, these data indicate that mannan (and PPME) inhibit splenic entry of lymphocytes by interacting with SSC, cell which play a critical role in the entry of lymphocytes into the spleen. Whether mannan-specific receptors on SSC directly mediate lymphocyte-SSC adhesion or play on indirect role in modifying lymphocyte migration requires further investigation.

The role of ultraviolet B-irradiated leukocyte transfusions and cyclosporine in intestinal transplantation.

To explore the efficacy of ultraviolet B-irradiated donor-specific leukocyte transfusions (UV-DSLT) with short-term cyclosporine to control intestinal allograft rejection, 75 adult Lewis (RT1l) rats underwent total small-intestinal transplantation from Brown-Norway (RT1n) donors. Recipients were randomly divided into ten treatment and control groups utilizing various combinations of donor-specific and third-party (Wistar-Furth, RT1u) leukocyte transfusions (TPLT), with or without transfusion UVB irradiation, and either alone or in combination with short-term cyclosporine administration (5 mg/kg intramuscularly on days -7, 0, 1, and 2 relative to transplantation). Leukocytes (10(8) cells) separated from a spleen cell suspension were infused on day -7. Certain transfused leukocytes were treated with 12,000 joules/m2 of UVB irradiation. Groups were monitored for mean survival time (MST) and cause of death. UV-DSLT alone (MST = 19.8 +/- 4.6) or in combination with cyclosporine (UV-DSLT+CsA, MST = 53.1 +/- 22.5) significantly (P less than 0.003-0.0002, Mantel-Cox) prolonged recipient survival when compared with appropriate controls (i.e., no treatment, MST = 11.2 +/- 3.4; CsA, MST = 17.2 +/- 9.0; UV-TPLT, MST = 12.4 +/- 4.0; and UV-TPLT+CsA, MST = 25.1 +/- 9.7) No significant increase in graft-versus-host disease occurred in any group, with 85% (64/75) of the recipients dying of acute rejection. Conversely, the UV-DSLT+CsA group had a significant increase (9/11; chi-square, P less than 0.0001) in chronic rejection. Because UV-DSLT+CsA improved survival as compared with third-party controls, a limited donor-specific unresponsiveness may have been induced. Furthermore, this treatment produces a consistent, chronic rejection rodent intestinal allograft model.