Selective triggering of human T and B lymphocytes in vitro by polyclonal mitogens

Very low concentration of lipopolysaccharide can induce the production of various cytokines and chemokines in human primary monocytes

OBJECTIVE

Lipopolysaccharide (LPS), a component of gram-negative bacteria, is a potent innate immune stimulus. The interaction of LPS with innate immune cells induces the production of proinflammatory cytokines and chemokines, thereby leading to the control of infection. In the present study, we investigated the effect of a wide range of LPS concentrations on the regulation of various proinflammatory cytokines and chemokines in human primary monocytes and T lymphocytes.

RESULTS

We demonstrated that a very low concentration of LPS could regulate the production of cytokines and chemokines in monocytes but not T lymphocytes. Unexpectedly, very low concentrations of LPS (0.0025 and 0.005 ng/mL) could induce TNF-α and IL-6 production, respectively, in monocytes. Our findings provide evidence that in the presence of monocytes, even very low endotoxin contamination could induce cytokine production. We suggest that the recombinant proteins used to investigate immune functions must be thoroughly screened for endotoxins using a highly sensitive method.

The cell body space occupied by the nucleus during the cell differentiation in human lymphocytic, granulocytic and erythroid cell lineages

The present nuclear and cell body diameter measurements demonstrated size differences of the approximate cell space estimate occupied by the cell nucleus during the cell differentiation in lymphocytic, granulocytic and erythroid cell lineages. These lineages were used as convenient models because all differentiation steps were easily identified and accessible in diagnostic peripheral blood or bone marrow smears of blood donors (BDs), patients suffering from chronic lymphocytic leukemia (CLL), patients with chronic myeloid leukemia (CML) and refractory anemia (RA) of the myelodysplastic syndrome (MDS). The cell space occupied by the nucleus was constant and did not change during the cell differentiation in the lymphocytic cell lineages of BDs and CLL patients despite the decreased cell size. In contrary, the cell space occupied by the nucleus markedly decreased in differentiating cells of granulocytic and erythroid lineages of patients suffering from CML. In the erythroid cell lineage in patients with RA of MDS the small reduction of the cell space occupied by the nucleus during the differentiation was not significant. The measurements also indicated that in progenitor cells of all studied cell lineages nuclei occupied more than 70 % of the cell space. Thus, the nucleus-cytoplasmic morphological and functional equilibrium appeared to be characteristic for each differentiation step and each specific cell lineage.

Immunophenotypic characteristics of multipotent mesenchymal stromal cells that affect the efficacy of their use in the prevention of acute graft vs host disease

BACKGROUND

Multipotent mesenchymal stromal cells (MSCs) are widely used in the clinic due to their unique properties, namely, their ability to differentiate in all mesenchymal directions and their immunomodulatory activity. Healthy donor MSCs were used to prevent the development of acute graft vs host disease (GVHD) after allogeneic bone marrow transplantation (allo-BMT). The administration of MSCs to patients was not always effective. The MSCs obtained from different donors have individual characteristics. The differences between MSC samples may affect their clinical efficacy.

AIM

To study the differences between effective and ineffective MSCs.

METHODS

MSCs derived from the bone marrow of a hematopoietic stem cells donor were injected intravenously into allo-BMT recipients for GVHD prophylaxis at the moment of blood cell reconstitution. Aliquots of 52 MSC samples that were administered to patients were examined, and the same cells were cultured in the presence of peripheral blood mononuclear cells (PBMCs) from a third-party donor or treated with the pro-inflammatory cytokines IL-1β, IFN and TNF. Flow cytometry revealed the immunophenotype of the nontreated MSCs, the MSCs cocultured with PBMCs for 4 d and the MSCs exposed to cytokines. The proportions of CD25-, CD146-, CD69-, HLA-DR- and PD-1-positive CD4+ and CD8+ cells and the distribution of various effector and memory cell subpopulations in the PBMCs cocultured with the MSCs were also determined.

RESULTS

Differences in the immunophenotypes of effective and ineffective MSCs were observed. In the effective samples, the mean fluorescence intensity (MFI) of HLA-ABC, HLA-DR, CD105, and CD146 was significantly higher. After MSCs were treated with IFN or cocultured with PBMCs, the HLA-ABC, HLA-DR, CD90 and CD54 MFI showed a stronger increase in the effective MSCs, which indicated an increase in the immunomodulatory activity of these cells. When PBMCs were cocultured with effective MSCs, the proportions of CD4+ and CD8+central memory cells significantly decreased, and the proportion of CD8+CD146+ lymphocytes increased more than in the subpopulations of lymphocytes cocultured with MSC samples that were ineffective in the prevention of GVHD; in addition, the proportion of CD8+effector memory lymphocytes decreased in the PBMCs cocultured with the effective MSC samples but increased in the PBMCs cocultured with the ineffective MSC samples. The proportion of CD4+CD146+ lymphocytes increased only when cocultured with the inefficient samples.

CONCLUSION

For the first time, differences were observed between MSC samples that were effective for GVHD prophylaxis and those that were ineffective. Thus, it was shown that the immunomodulatory activity of MSCs depends on the individual characteristics of the MSC population.

The immunostimulatory effects and chemical characteristics of heated honey

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese medicine (TCM), honey has been used as an additive in the heat-processing of herbal medicines to enhance their immunostimulatory activities.

AIM OF THE STUDY

We investigated the immunostimulatory activity of heated honey in vitro and in vivo.

MATERIALS AND METHODS

For the in vitro study, we compared the differences among the inducible effects of honey subjected to various heating conditions on granulocyte colony-stimulating factor (G-CSF) secretion from the cultured enterocytes and investigated the active ingredient. For the in vivo study, we conducted a survival test of mice infected by Streptococcus pyogenes with and without oral administration of heated honey.

RESULTS

We found that heating the honey induced the appearance of G-CSF secretions from the cultured enterocytes, and that this appearance depended on the heating temperature and time. No G-CSF secretions appeared when honey was not heated. Mice infected with Streptococcus pyogenes that were fed heated honey revealed prolonged survival. The active ingredient in heated honey was a high-molecular compound with about 730 kDa. When this compound was hydrolyzed, galactose, glucose, rhamnose, α-ribofuranose β-ribofuranose 1,5':1',5-dianhydride, and 5-hydroxymethylfurfural were generated.

CONCLUSIONS

Heated honey reveals immunostimulatory activity both in vitro and in vivo. These results support the scientific evidences of the TCM theory.

Effect of Priming of Multipotent Mesenchymal Stromal Cells with Interferon γ on Their Immunomodulating Properties

Multipotent mesenchymal stromal cells (MSCs) are widely used for cell therapy, in particular for prophylaxis and treatment of graft-versus-host disease. Due to their immunomodulatory properties, MSCs affect the composition of lymphocyte subpopulations, which depends on the immunological state of the organism and can change in different diseases and during treatment. Administration of MSCs is not always effective. Treatment of MSCs with different cytokines (in particular IFN-γ) leads to enhancement of their immunomodulatory properties. The aim of this study was to investigate subpopulational alterations and activation markers in lymphocytes (activated and non-activated) after interaction with MSCs and MSCs pretreated with IFN-γ (γMSCs) in vitro. Lymphocytes were co-cultured with MSCs or γMSCs for 4 days. The proportion of CD4+ and CD8⁺ expressing CD25, CD38, CD69, HLA-DR, and PD-1 and distribution of memory and effector subsets were measured by flow cytometry after co-cultivation of lymphocytes with MSCs or γMSCs. The distribution of lymphocyte subpopulations changes during culturing. In non-activated lymphocytes cultured without MSCs, decrease in the proportion of naïve cells and increase in the number of effector cells was observed. That could be explained as activation of lymphocytes in the presence of serum in culturing medium. Co-culturing of lymphocytes with MSCs and γMSCs leads to retention of their non-activated state. Activation of lymphocytes with phytohemagglutinin increases the number of central memory cells and activates marker expression. Interaction with MSCs and γMSCs prevents activation of lymphocytes and keeps their naïve state. Priming with IFN-γ did not induce MSCs inhibitory effect on activation of lymphocytes.

Crohn's disease-derived monocytes fail to induce Paneth cell defensins

Crohn's disease (CD) is associated with a multitude of genetic defects, many of which likely affect Paneth cell function. Paneth cells reside in the small intestine and produce antimicrobial peptides essential for the host barrier, principally human α-defensin 5 (HD5) and HD6. Patients with CD of the ileum are characterized by reduced constitutive expression of these peptides and, accordingly, compromised antimicrobial barrier function. Here, we present a previously unidentified regulatory mechanism of Paneth cell defensins. Using cultures of human ileal tissue, we showed that the secretome of peripheral blood mononuclear cells (PBMCs) from healthy controls restored the attenuated Paneth cell α-defensin expression characteristic of patients with ileal CD. Analysis of the Wnt pathway in both cultured biopsies and intestinal epithelial cells implicated Wnt ligands driving the PBMC effect, whereas various tested cytokines were ineffective. We further detected another defect in patients with ileal CD, because the PBMC secretomes derived from patients with CD were unable to restore the reduced HD5/HD6 expression. Accordingly, analysis of PBMC subtypes showed that monocytes of patients with CD express significantly lower levels of canonical Wnt ligands, including Wnt3, Wnt3a, Wnt1, and wntless Wnt ligand secretion mediator (Evi/Wls). These studies reveal an important cross-talk between bone marrow-derived cells and epithelial secretory Paneth cells. Defective Paneth cell-mediated innate immunity due to inadequate Wnt ligand stimulation by monocytes provides an additional mechanism in CD. Because defects of Paneth cell function stemming from various etiologies are overcome by Wnt ligands, this mechanism is a potential therapeutic target for this disease.

Induced expression of FcγRIIIa (CD16a) on CD4+ T cells triggers generation of IFN-γhigh subset

Whether or not CD4(+) T-cells express low affinity receptor FcγRIIIa (CD16a) in disease pathology has not been examined in great detail. In this study, we show that a subset of activated CD4(+) T-cells in humans express FcγRIIIa. The ligation of FcγRIIIa by immune complexes (ICs) in human CD4(+) T-cells produced co-stimulatory signal like CD28 that triggered IFN-γ production. The induced expression of FcγRIIIa on CD4(+) helper T-cells is an important finding since these receptors via ITAM contribute to intracellular signaling. The induced expression of FcγRIIIa on CD4(+) T helper cells and their ability to co-stimulate T-cell activation are important and novel findings that may reveal new pathways to regulate adaptive immune responses during inflammation and in autoimmunity.

Activin-A exerts a crucial anti-inflammatory role in neonatal infections

BACKGROUND

Activin-A is a cytokine with a critical role in infections and associated inflammation in experimental models and humans. Still, the effects of activin-A on neonatal infections remain elusive. Here, we investigated the expression of activin-A in the serum of septicemic preterm and term neonates and in peripheral blood leukocytes stimulated with inflammatory agents in vitro. The role of activin-A in the regulation of inflammatory responses by neonatal leukocytes was delineated.

METHODS

Peripheral blood was obtained from 37 septicemic neonates between the first and fifth days postinfection and from 35 healthy controls. Isolated monocytes and lymphocytes were stimulated with lipopolysaccharide (LPS) or phytohemagglutinin (PHA) in vitro in the presence of activin-A. Cell proliferation, cytokine, and chemokine release were investigated.

RESULTS

Activin-A was significantly increased in the serum of preterm septicemic neonates. Neonatal leukocytes secreted copious amounts of activin-A following stimulation, pointing to these cells as an essential source of activin-A in the circulation. Of note, treatment of neonatal leukocytes with activin-A during PHA and LPS stimulation resulted in significantly decreased interleukin (IL)-1β, IL-6, and CXCL8 production, concomitant with a striking increase in the anti-inflammatory mediator, IL-10.

CONCLUSION

Our findings uncover activin-A as a novel immunomodulatory agent critical for the control of inflammatory responses in septicemic neonates.

Peculiar tonsil-like structure near vagina of the laboratory shrew, Suncus murinus

After finding tonsil-like structures near the entrance of vagina of a laboratory shrew (Suncus murinus), which we subsequently designated as vaginal tonsils, we performed detailed immunohistochemical and developmental studies. The location of T and B cells in the vaginal tonsils differed from that in the palatine tonsils or that in the lymphoid nodes of other animals. The boundary between the germinal center region and the region encompassing follicular interfollicular tissue was not clear. B cells were widely distributed and very dense in the parenchyma, but they were scattered in the epithelial area (B cells were present in around 90% of the vaginal tonsil tissue). In contrast, T cells were scattered in the parenchyma and in the epithelial area (T cells were present in around 10% of the vaginal tonsil tissue). B cells were more prominent than T cells throughout the development of these structures and the epithelium was invaded by many immigrating cells. The size of the vaginal tonsils changed during postnatal development. Vaginal tonsils are structurally similar to other tonsils, and they may function to protect the vagina from infection.

Effects of natural eggshell membrane (NEM) on cytokine production in cultures of peripheral blood mononuclear cells: increased suppression of tumor necrosis factor-α levels after in vitro digestion

Tumor necrosis factor-α (TNF-α) plays an important role in inflammatory processes. This study examined the effects of natural eggshell membrane (NEM(®)) (ESM Technologies, LLC, Carthage, MO, USA) on interleukin (IL)-2, IL-4, IL-6, IL-10, interferon-γ (IFN-γ), and TNF-α cytokine production by 4-day peripheral blood mononuclear cell (PBMC) cultures exposed to serial dilutions of either an aqueous extract of natural eggshell membrane (NEM-AQ) or NEM subjected to in vitro digestion (NEM-IVD). The effects on cytokine production were also assessed in the presence of phytohemagglutinin (PHA) and pokeweed mitogen (PWM) where exposure to NEM-AQ resulted in reduced levels of proliferation and statistically significant effects on IL-6, IL-10, IFN-γ, and TNF-α cytokine production. NEM-AQ reduced levels of IL-6, IL-10, IFN-γ, and TNF-α in cultures exposed to PHA. In cultures containing PWM, NEM-AQ reduced production of IL-10 and at the highest dose tested increased IL-6 and decreased TNF-α cytokine levels. NEM-IVD, at the two lowest concentrations of product, significantly reduced TNF-α production by PBMC cultures exposed to PWM compared with the in vitro digest control or native NEM. Taken together, these results suggest that NEM-AQ can influence signaling events in response to the T cell-specific mitogen PHA as well as to the mitogen PWM that require cellular cross-talk and that these effects may be partially mediated through a reduction in level of the pro-inflammatory cytokine TNF-α. The suppression of TNF-α production in the presence of NEM-IVD is promising for the use of NEM as a consumable anti-inflammatory product.

Differentiation of human peripheral blood Vδ1+ T cells expressing the natural cytotoxicity receptor NKp30 for recognition of lymphoid leukemia cells

The success of cancer immunotherapy depends on productive tumor cell recognition by killer lymphocytes. γδ T cells are a population of innate-like lymphocytes endowed with strong, MHC-unrestricted cytotoxicity against tumor cells. This notwithstanding, we recently showed that a large proportion of human hematologic tumors is resistant to γδ peripheral blood lymphocytes (PBLs) activated with specific agonists to the highly prevalent Vγ9Vδ2 TCR. Although this probably constitutes an important limitation to current γδ T cell–mediated immunotherapy strategies, we describe here the differentiation of a novel subset of Vδ2− Vδ1+ PBLs expressing natural cytotoxicity receptors (NCRs) that directly mediate killing of leukemia cell lines and chronic lymphocytic leukemia patient neoplastic cells. We show that Vδ1+ T cells can be selectively induced to express NKp30, NKp44 and NKp46, through a process that requires functional phosphatidylinositol 3-kinase (PI-3K)/AKT signaling on stimulation with γc cytokines and TCR agonists. The stable expression of NCRs is associated with high levels of granzyme B and enhanced cytotoxicity against lymphoid leukemia cells. Specific gain-of-function and loss-of-function experiments demonstrated that NKp30 makes the most important contribution to TCR-independent leukemia cell recognition. Thus, NKp30+ Vδ1+ T cells constitute a novel, inducible and specialized killer lymphocyte population with high potential for immunotherapy of human cancer.

Receptors and signaling mechanisms for B-lymphocyte activation, proliferation and differentiation--insights from both in vivo and in vitro approaches

During the last three decades, a number of B-lymphocyte specific surface antigens have been defined some of which may also show activation/differentiation specific expression. Here, we review the various signaling events and the receptor-ligand interactions for B-cell development, activation and differentiation. Our discussion and presentation include reviewing the in vivo and in vitro mechanisms. Focus is on the experiments that give us valuable insights into the B cell signaling mechanisms in vitro. Three significant pathways in B-cell development - c-Kit, FLT-3 and IL-7 signaling pathways are elucidated upon. Both antigen dependent and antigen independent mechanisms of B cell stimulation are also reviewed.

Structure and function of the nicotinic arm of acetylcholine regulatory axis in human leukemic T cells

Although acetylcholine (ACh) is widely known as a neurotransmitter, it also functions as a local humoral factor translating environmental stimuli into alterations in T cell development and function. The cholinergic components present in neurons are expressed in T cells where they constitute an independent cholinergic system. Both non-immunologic and immunologic stimulations can alter expression and function of cholinergic elements in T cells. Recent studies have convincingly demonstrated regulation of immune system by auto/paracrine ACh, which provides a basis for development of new immunomodulatory therapies with nicotinic agonists. The purpose of our research is to integrate information about the structure and activity of the ACh regulatory axis with the phenotypic and functional alterations of T cells during their development and commitment. In this study, we used the Ach producing human leukemic T cell line CCRF-CEM (CEM) to investigate auto/paracrine mechanisms of T cell regulation through the nicotinic class of ACh receptors (nAChRs). The intact CEM expressed alpha3, alpha5, alpha6, alpha7, alpha 9, beta2 and beta4 nAChR subunits. Stimulation of CEM with 10 microg/ml of phytohemagglutinin (PHA) for 16 h upregulated expression of the alpha3, alpha5, alpha7, alpha9 and beta2 and downregulated that of alpha6 and beta4 subunits, indicating that TCR activation leads to overexpression of high Ca2+-permeable ACh-gated ion channels. Activation of alpha7- and alpha3 AChRs predominantly abrogated PHA-dependent upregulation of the pro-inflammatory cytokine TNF-alpha and IFN-gamma receptors, respectively, at the mRNA and protein levels. Signaling through alpha7 and alpha3 nAChRs also significantly (p<0.05) altered expression of the cell state regulators p21 and Bcl-2, respectively, suggesting that downregulation of inflammation via nAChRs includes effects on the T cell cycle progression and apoptosis. These findings indicate that constant stimulation of alpha7 and alpha3 nAChRs by endogenously released ACh controls T cell activation and that signaling downstream of distinct nAChR subtypes targets specific inflammatory and cell cycle genes. Learning the cholinergic pharmacology of inflammation should allow to regulate specific types of immune reactions by selectively activating or blocking the types of nAChRs expressed by the immune cells mediating specific immune reactions.

B-Lymphoma cells with epigenetic silencing of Pax5 trans-differentiate into macrophages, but not other hematopoietic lineages

In mice, zygotic or pro-B-cell-specific knock-out of the Pax5 gene allows differentiation of pro-B-cells into all hematopoietic lineages. We previously generated and characterized a murine B-cell lymphoma, dubbed Myc5, whose cells spontaneously lose Pax5 expression when cultured in vitro, but regain it when re-injected into syngeneic mice. In cultured Myc5 cells, the loss of Pax5 correlates with the acquisition of myeloid markers, such as CD11b and F4/80. Here, we sought to determine whether these cells are truly B-macrophage-restricted or, like Pax5-null progenitors, can give rise to additional hematopoietic lineages. In vitro differentiation assays with various cytokines showed that Myc5 cells do not differentiate into NK cells, dendritic cells, neutrophils, or osteoclasts. At the same time, in the presence of macrophage colony-stimulating factor (M-CSF), they readily phagocytose latex beads and provide T-cell help. Both phenomena are indicative of the bona fide macrophage phenotype. Conversely, enforced Pax5 re-expression in macrophage-like Myc5 cells led to down-regulation of the M-CSF receptor and re-acquisition of some B-cell surface markers (e.g., CD79a) and lineage-specific transcription factors (e.g., IRF4 and Blimp). Retrovirally encoded Pax5 also restored expression of several master B-cell differentiation proteins, such as the IL-7 receptor and transcription factor E2A. In contrast, levels of EBF were unaffected by Pax5 suggesting that EBF acts exclusively upstream of Pax5 and might contribute to Pax5 expression. Indeed, transduction with an EBF-encoding retrovirus partly reactivated endogenous Pax5. Our data reveal the complex relationship between B-cell-specific transcription factors and suggest the existence of numerous feedback mechanisms.

Mitogenic properties of pokeweed lectin-D isoforms on human peripheral blood lymphocytes: non-mitogen PL-D1 and mitogen PL-D2

We investigated native structures and mitogenic properties of pokeweed lectin-D isoforms (PL-D1 and -D2) on human peripheral blood lymphocytes along with other isolectins (PL-A to -C). Both native PL-D isoforms appeared to behave as monomers. PL-D2 proliferated the lymphocytes like PL-C, whereas PL-D1 had no mitogenicity. PL-D1 acquired mitogenic activity after trimming of the C-terminal dipeptide.

Regulation of soluble and surface-bound TRAIL in human T cells, B cells, and monocytes

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF/nerve growth factor superfamily that, apart from inducing cell death in susceptible cells, displays immunoregulatory functions influencing, for instance, T cell proliferation. It can be found in two forms: membrane-bound and soluble protein. The regulation of these is still not fully understood. In this study, we have analyzed the regulation of TRAIL surface expression and secretion in human T cells, B cells, and monocytes in response to specific stimuli. T cells, B cells, and monocytes were cultured in the presence of phytohemagglutinin (PHA)+interleukin (IL-2), anti-CD40+IL-4, and lipopolysaccharide (LPS), respectively. In particular, not only PHA+IL-2 but also LPS were able to induce secretion of soluble TRAIL, but did not enhance the expression of surface-bound TRAIL. Simultaneously, we investigated the effect of the pleiotropic stimulus interferon (IFN)-beta, known to target all leukocyte subsets, on TRAIL. Predominantly, monocytes were affected by IFN-beta, causing both release of soluble TRAIL and upregulation of the surface-bound form. IFN-beta, however, did not cause any upregulation of TRAIL in T cells. Our data serve as a basis to better understand the complex regulation of TRAIL in human peripheral immune cells and might help to clarify the role of the TRAIL system in immunopathology.

Endotoxins of enteric pathogens modulate the functions of human neutrophils and lymphocytes

The locomotor responses of human peripheral blood neutrophils and lymphocytes were measured by the change from spherical to polarized shapes in the presence of endotoxins (lipopolysaccharide, LPS) of enteric pathogens: S. dysenteriae type 1, V. cholerae Inaba 569B, S. typhimurium, and K. pneumoniae. We reported earlier that these endotoxins are chemotactic factors for the neutrophils since they stimulated cell polarization within a few minutes of incubation. Endotoxins had an inhibitory effect upon neutrophil phagocytosis of opsonized yeast and the cells engulfed fewer yeasts. Interestingly, endotoxins increased neutrophil adhesion to clean glass surfaces, but stimulated the cells to exhibit increased random locomotion (chemokinesis) through cellulose nitrate filters and show an enhanced ability to reduce nitroblue tetrazolium (NBT) dye. Unlike neutrophils, lymphocytes direct from blood do not show polarized morphology towards chemotactic factors but the cells acquire locomotor capacity during 24-72 h culture with mitogens such as phytohemagglutinin (PHA), phorbol myristate acetate or concanavalin A. Stimulation of blood lymphocytes with endotoxins did not induce cell polarization in short-term but long-term culture resulted in an increase in the proportion of polarized cells that acquired locomotor morphologies. The majority of these cells were identified as esterase negative B-lymphocytes that migrated through filters. Despite the optimum time of incubation for each of these cell types being different, we found that lymphocytes respond to much lower concentrations of endotoxins than the neutrophils. These findings suggest that endotoxins of enteric pathogens modulate the functions of human blood neutrophils and lymphocytes.

Immunomodulatory effects of human foetal liver-derived mesenchymal stem cells

Adult mesenchymal stem cells (MSCs) have been suggested to decrease lymphocyte proliferation in vitro. We hypothesised that foetal MSCs (fMSCs) would have an immunosuppressive effect on allograft responses in vitro. Human MSCs were isolated and cultured from first-trimester foetal livers and characterised by flow cytometry. fMSC stained positive for CD29, CD44, CD166, CD105, SH-3 and SH-4, and negative for CD14, CD34 and CD45. When plated on adipogenic, chondrogenic and osteogenic media, fMSC differentiated into the respective cell lineage. Compared to adult MSC (aMSC), the proliferative capacity of fMSC was higher. Mitogen stimulation of PBL was inhibited by fMSC. The greatest inhibition (78%) was seen when 30,000 fMSCs were added to 150,000 lymphocytes stimulated by phytohaemagglutinin. Adult and fMSCs were added to mixed lymphocyte cultures (MLC) containing peripheral blood lymphocytes or foetal liver cells. Unlike aMSC, fMSCs did not inhibit MLC. fMSC could be culture-expanded several million folds with no loss of phenotype characteristics, which makes them ideal for ex vivo expansion. fMSC inhibit lymphocyte proliferation induced by mitogens, but not alloreactivity as measured by MLC.

Mesenchymal stem cells inhibit and stimulate mixed lymphocyte cultures and mitogenic responses independently of the major histocompatibility complex

We aimed to study the effects of mesenchymal stem cells (MSCs) on alloreactivity and effects of T-cell activation on human peripheral blood lymphocytes (PBLs) in vitro. MSCs were expanded from the bone marrow of healthy subjects. MSCs isolated from second to third passage were positive for CD166, CD105, CD44, CD29, SH-3 and SH-4, but negative for CD34 and CD45. MSCs cultured in osteogenic, adipogenic or chondrogenic media differentiated, respectively, into osteocytes, adipocytes or chondrocytes. MSC added to PBL cultures had various effects, ranging from slight inhibition to stimulation of DNA synthesis. The stimulation index (SI = (PBL + MSC)/PBL) varied between 0.2 and 7.3. The SI was not affected by the MSC dose or by the addition of allogeneic or autologous MSCs to the lymphocytes. Suppression of proliferative activity was observed in all experiments after the addition of 10,000-40,000 MSCs to mixed lymphocyte cultures (MLCs). Lymphocyte proliferation was 10-90%, compared with a control MLC run in parallel without MSCs. In contrast, the addition of fewer MSCs (10-1000 cells) led to a less consistent suppression or a marked lymphocyte proliferation in several experiments, ranging from 40 to 190% of the maximal lymphocyte proliferation in control MLCs. The ability to inhibit or stimulate T-cell alloresponses appeared to be independent of the major histocompatibility complex, as results were similar using 'third party' MSCs or MSCs that were autologous to the responder or stimulating PBLs. The strongest inhibitory effect was seen if MSCs were added at the beginning of the 6 day culture, and the effect declined if MSCs were added on day 3 or 5. Marked inhibitory effects of allogeneic and autologous MSCs (15,000) were also noted after mitogenic lymphocyte stimulation by phytohaemagglutinin (median lymphocyte proliferation of 30% of controls), Concanavalin A (56%) and protein A (65%). Little, if any, inhibition occurred after stimulation with pokeweed mitogen. Low numbers of MSCs (150 cells) were unable to inhibit mitogen-induced T-cell responses. MSCs have significant immune modulatory effects on MLCs and after mitogenic stimulation of PBL. High numbers of MSCs suppress alloreactive T cells, whereas very low numbers clearly stimulated lymphocyte proliferation in some experiments. The effect of a larger number of MSCs on MLCs seems more dependent on cell dose than histocompatibility and could result from an 'overload' of a stimulatory mechanism.

Effect of dithiocarbamate pesticide zineb and its commercial formulation, azzurro. II. micronucleus induction in immunophenotyped human lymphocytes

The frequency of micronuclei was measured in human peripheral B-lymphocytes and some T-lymphocyte subpopulations exposed in vitro to 1.0-100.0 microg/ml of the dithiocarbamate pesticide zineb and its commercial formulation azzurro. The peripheral mononuclear lymphocytes were stimulated in vitro with phytohemagglutinin after pesticide treatment and B-lymphocytes and the various T-lymphocyte subsets were classified by the MAC (morphology, antibody, chromosomes) method, which allows the immunological identification of different cell lineages. An increased frequency of micronuclei in CD20(+) (P < 0.01), CD3(+) (P < 0.01), and CD8(+) lymphocytes (P < 0.01) was observed only when 25.0 microg/ml of zineb and azzurro were employed. The frequency of micronuclei in treated CD8(+) cells did not differ from treated CD20(+) lymphocytes (P > 0.05). Lower concentrations of pesticides did not increase the frequency of micronuclei from that observed in control cultures. Furthermore, for both zineb and azzurro cytotoxicity was observed at doses higher than 50.0 microg/ml. Significant increases in the proportion of CD20(+) (P < 0.01) and CD8(+) cells (P < 0.01) among mitotic and interphasic lymphocytes from both zineb- and azzurro-treated cultures were observed only when a concentration of 25.0 microg/ml was employed. In contrast, significant decreases in the proportion of CD3(+) (P < 0.01) and CD4(+) cells (P < 0.01) were found for both mitotic and interphasic lymphocytes from zineb- and azzurro-treated cultures. The MAC methodology revealed that among the different lymphocyte subpopulations analyzed (CD20, CD3, CD4, and CD8), the induction of micronuclei by zineb and its commercial formulation azzurro was restricted to CD20(+) B-cells and T-suppressor/cytotoxic CD8(+) lymphocytes.

Induction of proliferation and cytokine production in human T lymphocytes by lipopolysaccharide (LPS)

Lipopolysaccharide (LPS), also known as endotoxin, is a compound of the cell wall of Gram-negative bacteria, which has been demonstrated to induce inflammatory reactions in vitro as well as in vivo, including lethal shock. A great number of different cells have been documented to be reactive to LPS, e.g. monocytes/macrophages, vascular cells, polymorphonuclear cells, and even B lymphocytes. We have now established that T lymphocytes could also contribute to an inflammatory reaction to LPS. LPS is a potent inducer of human T-lymphocyte proliferation and cytokine production. The activation of T lymphocytes by LPS requires direct cell-to-cell contact with viable accessory monocytes. This interaction was found to be MHC-unrestricted, but strongly dependent on costimulatory signals provided by B7/CD28 interactions. The frequency of responding T lymphocytes is less than 1:1000. A very exciting finding was that not only monocytes, but also CD34+ hematopoietic stem cells, which circulate in peripheral blood in very low frequency, exert essential accessory cell activity during stimulation of T lymphocytes by LPS. In contrast, the response of T lymphocytes to conventional recall antigens is not controlled by blood stem cells. These conclusions are based on the observation that depletion of CD34-positive blood stem cells resulted in a complete loss of LPS-induced T-lymphocyte stimulation. Addition of CD34-enriched blood stem cells led to a recovery of reactivity of T lymphocyte to LPS. The characteristics of T-lymphocyte activation indicate that LPS is neither active as a mitogen, or as a superantigen, or as a classical antigen, but may activate T lymphocyte through a new, so far undescribed, mechanism. Furthermore, the involvement of hematopoietic blood stem cells in the activation of T lymphocytes by LPS demonstrates a role of these cells in inflammatory and immunological events.

CD34(+) hematopoietic stem cells exert accessory function in lipopolysaccharide-induced T cell stimulation and CD80 expression on monocytes

CD34(+) hematopoietic stem cells, which circulate in peripheral blood with very low frequency, exert essential accessory function during lipopolysaccharide (LPS)-induced human T lymphocyte activation, resulting in interferon gamma production and proliferation. In contrast, stimulation of T cells by "conventional" recall antigens is not controlled by blood stem cells. These conclusions are based on the observation that depletion of CD34(+) blood stem cells results in a loss of LPS-induced T cell stimulation as well as reduced expression of CD80 antigen on monocytes. The addition of CD34-enriched blood stem cells resulted in a recovery of reactivity of T cells and monocytes to LPS. Blood stem cells could be replaced by the hematopoietic stem cell line KG-1a. These findings may be of relevance for high risk patients treated with stem cells or stem cell recruiting compounds and for patients suffering from endotoxin-mediated diseases.

Biomechanical and morphological studies on osseointegration in immunological arthritis in rabbits

The biomechanics and morphology of the interface between bone tissue and threaded, commercially pure titanium implants were studied i an experimental model of monoarticular arthritis in New Zealand white rabbits (n = 8). Two of the eight rabbits died before evaluation. Immunisation with bovine serum albumin (BSA) and repeated intra-articular injections with BSA in one knee joint elicited an immune response and clinical signs of inflammation. The opposite joint was injected with saline. Three implants were inserted intra-articularly in the lateral femoral condyle in each joint. After a period of six weeks the stability of two of the three implants was evaluated by pull-out and torsion tests using a standardised biomechanical model. The rabbits were killed by perfusion fixation, and the implants and surrounding tissue were retrieved en bloc for histological analysis. The amount of bone, the degree of bone apposition, and the biomechanical evaluation showed that the absolute mechanical capacity of anchorage was not significantly reduced on the arthritic side compared with the control knees. These results indicate that it might be possible to obtain osseointegration in juxta-articular bone despite local joint inflammation.

Pseudomonas aeruginosa exoenzyme S induces proliferation of human T lymphocytes

Pseudomonas aeruginosa is a gram-negative bacterium that is responsible for devastating acute and chronic infections, which include bronchiectasis in cystic fibrosis, nosocomial pneumonia, and infection of burn wounds. Previous studies have demonstrated that these patients have impaired host responses, including cell-mediated immune responses, which are important in anti-Pseudomonas host defense. The P. aeruginosa exoproduct, exoenzyme S, has a number of characteristics which suggest that it might be important in cell-mediated immunity. To determine whether exoenzyme S activates lymphocytes to proliferate, peripheral blood mononuclear cells (PBMC) from normal volunteers were stimulated with purified exoenzyme S, and the lymphocyte response was assessed by measuring [3H]thymidine uptake and by counting the number of cells after various times in culture. Ninety-five percent of healthy adult donors had a lymphocyte response to exoenzyme S. The optimal lymphocyte response occurred on day 7, with 4 x 10(5) PBMC per microtiter well when cells were stimulated with 10 micrograms exoenzyme S per ml. [3H]thymidine uptake correlated with an increase in the number of mononuclear cells, indicating that proliferation occurred. In unseparated PBMC, T cells, and to a lesser extent B cells, proliferated. Purified T cells proliferated, while purified B cells proliferated only after the addition of irradiated T cells. Thus, T lymphocytes are necessary and sufficient for the proliferative response to exoenzyme S. We speculate that exoenzyme S from P. aeruginosa is important in T-lymphocyte-mediated host defense to P. aeruginosa. In strategies to enhance impaired cell-mediated immunity, exoenzyme S should be considered as a potential stimulant.

Relative immunocompetence of the newborn harbour seal, Phoca vitulina

The immune system of many mammalian species is not fully developed at birth, with newborns obtaining temporary immunological protection from maternal antibodies. Little is known of the immune system of the harbour seal, and developmental aspects of its immune system have not been systematically studied. We collected blood and milk samples from nine free-ranging mother-pup pairs throughout the lactation period on Sable Island, Canada, in an effort to characterise developmental aspects of the immune system of this newborn pinniped. Pup lymphocytes responded stronger to the mitogens concanavalin A, phytohaemagglutinin, and pokeweed mitogen than the lymphocytes of their mothers. In contrast to newborn cats and dogs, newborn seal pups developed high specific antibody responses after immunisation with an inactivated rabies vaccine. Circulating levels of total IgG in newborn pups were low (3% of maternal levels), but increased rapidly after colostrum intake (to 65% of maternal levels after 15 days). A similar pattern of increase in pup serum was observed for phocine distemper virus specific antibodies which had been detected in the serum and milk of mothers, suggesting that the transfer of colostral antibodies is an important feature of temporary protection for the pup. We speculate that the relative immunocompetence of the harbour seal at birth reflects an adaptation to its relatively short nursing period and limited maternal care.

Mitogen and antigen induced B and T cell responses of peripheral blood mononuclear cells from the harbour seal (Phoca vitulina)

In vitro assays were developed for studies concerning the functioning of the immune system of the harbour seal (Phoca vitulina). Proliferative responses of peripheral blood mononuclear cells (PBMC) were measured after stimulation with different concentrations of the mitogens concanavalin A (Con A), pokeweed mitogen (PWM), phytohaemagglutinin (PHA) or lipopolysaccharide from Salmonella typhimurium (LPS). Con A and PWM induced strong proliferative responses, while PHA and LPS induced comparatively low proliferative responses. Responses of mitogen stimulated PBMC to recombinant human interleukin-2 (rhIL-2) and in vitro immunoglobulin production by mitogen stimulated PBMC were measured to discriminate between stimulation of T cells and B cells. It was found that Con A and PHA stimulate phocine T cells, PWM stimulates both T cells and B cells and LPS predominantly stimulates phocine B cells. Antigen-specific immune responses were measured after immunization of seals with an inactivated rabies vaccine and/or with tetanus toxoid. Antigen-specific proliferation of PBMC and the presence of antigen-specific antibody forming cells were demonstrated for both antigens in the PBMC of immunized animals. The responses measured in vitro correlated well with the development of specific serum antibody titers to these antigens.

Tissue response to titanium implants in experimental antigen-induced arthritis

The healing of threaded, non-alloyed titanium implants in bone was studied in an experimental model of monoarticular arthritis in New Zealand white rabbits. Immunization with bovine serum albumin (BSA) and repeated intra-articular injections with BSA elicited an immune response and clinical signs of inflammation. Implants were inserted and 6 wk after surgery, with full weight-bearing, the rabbits were killed by perfusion fixation. Light microscopic morphometry showed that the cartilage was thinner and the subchondral bone had a lower density in the arthritic joints compared to the control side. The titanium implants in the arthritic joints had a lesser degree of mineralized bone-implant contact and surrounding bone than the implants inserted in control joints. The present study shows that the healing of titanium implants in the rabbit knee joint is impaired in experimental immunologic arthritis. This model may be useful for the study of biomaterial-tissue interactions under pathological conditions.

Radiation induced micronuclei in subpopulations of human lymphocytes

The micronucleus expression in T-helper, T-suppressor and B lymphocytes of the peripheral blood was studied after in vitro exposure to high (2.5 Gy and 5 Gy) and low (0.5 Gy and 1 Gy) doses of ionizing radiation. Investigations were carried out by combining the micronucleus assay with immunofluorescence staining using subpopulation specific antibodies. While in the higher dose range B cell proliferation was inhibited nearly completely-so that micronuclei could not be expressed-we found after exposure to lower doses that B cells were the lymphocyte subpopulation which was most sensitive to micronucleus induction. Among the T cell population, the T-suppressor subset revealed a higher yield of micronuclei than T-helper cells, whereas with regard to the effect of radiation on proliferative ability, T-helper cells reacted more sensitivity than the T-suppressor lymphocytes. Our studies provide insight into the effect of radiation exposure on the micronucleus expression of lymphocyte subpopulations and new information which may be useful for the further development of biological dosimetry.

The effect of Lasso herbicide on human immune function as measured by in vitro assays

Using in vitro assays, this study was undertaken to determine whether the components of Lasso herbicide formulation had an effect on the human immune system. Mononuclear cells from human peripheral blood were exposed to analytical alachlor, alachlor conjugated to human serum albumin or Lasso formulation over a concentration range from .01 microM-1.0 microM. The effects of the test materials on the following immunological functions were determined: lymphocyte proliferation induced by mitogen or antigen; antibody synthesis of IgG and IgM isotypes in pokeweed stimulated mononuclear cell cultures; cytotoxic T cell proliferation; lysis of target cells by natural killer cells and lymphokine activated killer cells. The data demonstrated that the test compounds had no significant, dose related effect on the function of immunocompetent cells. Hence, the data suggest that the components of the Lasso formulation have no effect on the human immune system.

Effects of endometrial IgG on PHA-induced T cell mitogenesis

To clarify the characterization and immunologic mechanisms of endometrial extract as a suppressive factor in tissues of the implantation site, the effects of endometrial extract and IgG on mitogen-stimulated cultures of lymphocytes from human peripheral blood were investigated. The inhibitory activity of endometrial extracts was observed to be augmented markedly in the secretory phase of the menstrual cycle as compared to the proliferative phase. Secretory endometrial extract, at a concentration of 0.6 mg protein/ml, caused 50% suppression of PHA-induced lymphocyte blastogenesis (PHA-BL). Column fractionation of endometrial extract on a Sephadex G-200 column showed a profile with three peak fractions and demonstrated that the 2nd peak fraction was mainly responsible for the suppression of PHA-BL. The 2nd peak fraction was shown to contain IgG by the method of immunodiffusion with anti-human IgG. The 2nd peak fraction from which IgG was removed with affinity chromatography caused significant depression of PHA-BL. Furthermore, the Fc fraction of IgG showed marked suppression compared to the F(ab')2 fraction. From these results, we suggest the possibility of an endogenous substance containing IgG as a suppressive factor which is implicated in the suppression of T cell function. The Fc fragment seemed to be the major fraction possessing such suppressive activity.

Production of IgG and IgM autoantibody to the alternative pathway C3 convertase in normal individuals and patients with membranoproliferative glomerulonephritis

To understand the origin of autoantibody production, we studied the ontogeny of antibody to the alternative pathway C3 convertase (C3 nephritic factor or C3NeF). Peripheral blood mononuclear cells from newborns, normal adults, and patients with membranoproliferative glomerulonephritis produced IgM and IgG C3NeF after culture for 14 days with pokeweed mitogen. Both IgM and IgG moieties appear to have the same paratope and are able to inhibit each other's binding and function. The affinity constant for each of the C3NeF molecules was moderately high (10(8) liters/mol) and there appeared to be little difference between the Ka values for the IgG and the IgM autoantibodies or between Ka values for autoantibodies isolated from newborns, adults, and patients. These data, then, indicate that the ability to produce C3NeF autoantibody is present from the time of birth in normal individuals. The high affinity of these autoantibodies under normal conditions suggests that C3NeF may play a more important physiological role than previously anticipated.

Frequencies of interleukin-5 mRNA-producing cells in healthy individuals and in immunoglobulin-deficient patients, measured by in situ hybridization

Interleukin-5 (IL-5) has previously been demonstrated to enhance immunoglobulin synthesis, especially IgA. Thus, it could be hypothesized that a defect production of IL-5 may cause immunoglobulin deficiency. We have analysed the frequency of IL-5 mRNA-producing cells in healthy adults and in patients with common variable immunodeficiency or selective IgA deficiency. Unstimulated lymphocytes were rarely found to synthesize IL-5 as measured by in situ hybridization. However, pokeweed mitogen and several other activating ligands induced the synthesis of IL-5 mRNA in peripheral blood and spleen lymphocyte cultures. After pokeweed mitogen activation, the number of IL-5 mRNA-producing cells most often peaked on day 3 with a maximal frequency of around 1-2% of mononuclear cells. In a kinetic study we were unable to detect any peak frequency differences between healthy controls (mean 0.44%) and 20 patients (mean 0.58%). Thus, although IL-5 has been reported to be an important regulator of IgA synthesis, a defect production does not seem to be the underlying mechanism in human immunoglobulin deficiency.

Phenotypic analysis of human peripheral blood lymphocytes by automatic sampling flow cytometry after stimulation with mitogens or allogeneic cells

Human peripheral blood lymphocyte (PBL) phenotypes have been analyzed before and after stimulation with phytohemagglutinin (PHA), concanavalin A (ConA) and pokeweed mitogen (PWM) for 3 days and in mixed lymphocyte culture (MLC) for 7 days. PBL labeled with each of 10 fluorescent monoclonal antibodies were automatically sampled for flow cytometry from 96-well microtiter plates using a microsample delivery system. The reference phenotypic ranges were determined in fresh cells and control cultures. PHA was mostly mitogenic for T PBL bearing the CD3, CD5, CD7, CD8 and CD25 differentiation clusters, and a low density of CD1 and CD4 had a small effect on human natural killer cells (HNK) and also did not stimulate B (CD19) and HLA-DR+ PBL. There was an incomplete phenotypic overlapping between PHA- and ConA-stimulated cultures, ConA being more mitogenic for CD4 and less mitogenic for CD8 PBL. The mitogenic effect of PWM was evident on CD3, CD5, CD7, CD4, CD25 and CD8, but not on HNK, HLA-DR and CD19 B PBL, which presumably had already differentiated into antibody-secreting cells. After MLC stimulation all T, B and HNK PBL subsets tested were increased, but the cells bearing CD1, CD4, CD5, CD7, CD25, HNK, CD19 and HLA-DR had the greatest proliferation with respect to the unmixed control PBL. The present approach to the phenotyping of PBL subsets could offer more complete and accurate data for monitoring and follow-up of patients in transplantation and immunopathology hospital wards.

Evidence that production of autoantibody to the alternative pathway C3 convertase is a normal physiologic event

The origin of autoantibody production was studied with the use of antibody to the alternative pathway C3 convertase (C3 nephritic factor (C3NeF), as a model. Pokeweed mitogen stimulation of peripheral mononuclear cells from newborn infants, normal adults, and patients with membranoproliferative glomerulonephritis indicated that the ability to make C3NeF is apparently present in everyone from the time of birth. In addition, C3NeF appeared to express a single or very limited idiotope (21/21 isolates). The data also suggest that the elaboration of C3NeF may approximate an antibody response after immunization. Thus the C3NeF fraction of the total IgG or IgM produced in culture by pokeweed mitogen-stimulated mononuclear cells from normal neonates and adults, as well as from patients, was in the range of the production of specific antibody. Further, both IgG and IgM C3NeF produced by cells from these normal individuals, including newborn infants, had an affinity for antigen (10(8) to 10(9) L/mol) that was also in the range of specific antibody. Most of the autoantibody molecules (5/7) from serum were IgG3; two B cell clones producing C3NeF were CD5-negative. These experiments indicate that unmutated germline genes are used in the production of C3NeF and that a limited spectrum of antiidiotypic antibodies regulate its production.

Cell surface molecules involved in early events in T-cell mitogenic stimulation by staphylococcal enterotoxins

We tested the mitogenic response to staphylococcal enterotoxin (SE) type A and SE type B in spleen cells from five strains of mice and found consistent and significant differences among the strains. We chose to study the mitogenic responses of two of these strains, C58BL/6J and BALB/cJ, in greater detail. We investigated the effects of specific monoclonal antibodies to cell surface determinants on SE-induced mitogenesis. Monoclonal antibodies against Ia (class II major histocompatibility complex) determinants blocked SE-induced mitogenesis. Both I-A and I-E molecules can participate in the stimulation, and in BALB/cJ mice which express both types of class II molecules both must be blocked to prevent mitogenesis. Mitogenesis was not inhibited by monoclonal antibodies specific for class I major histocompatibility complex antigens or monoclonal antibodies specific for Mac-1, Lyt-1, or Lyt-2 cell surface proteins. Monoclonal antibodies specific for the T-cell surface antigens L3T4 and T3 also substantially inhibited SE-induced mitogenesis. This implicates participation of the T-cell antigen receptor complex in stimulation induced by the SEs. Elimination of L3T4+ helper-inducer T cells abolished the mitogenic response of spleen cells to SE. Reconstitution of L3T4-depleted spleen cells with L3T4+ T cells showed that the level of the mitogenic response was directly proportional to the number of L3T4+ cells added. Elimination of Lyt-2+ cells resulted in a 50% decrease in the response to SEs. These results indicate that L3T4+ T cells are required for the mitogenic response to SE, but both L3T4+ and Lyt 2+ T cells participate in SE-induced mitogenesis. Our results suggest that both Ia and the T-cell antigenic receptor complex are involved in SE-induced mitogenesis.

DNA analysis of stimulated lymphocytes by automatic sampling for flow cytometry

A microsample delivery system (MSDS) was tested for automatic flow cytometry (FCM) analysis of DNA synthesis in stimulated human peripheral blood lymphocytes (PBL) cultivated in wells of microtiter plates. After incubation, either for 1-3 days with phytohemagglutinin, concanavalin A, and pokeweed mitogen, or for 7 days with allogenic PBL, the cells, while in the wells, were washed in hypotonic Tris buffer and stained with ethidium bromide-RNAse solution. The results obtained from quintuplicate replicated wells, each of the five containing the same control or stimulated cultures, were reproducible in terms of the number of nuclei counted in each histogram of control, mitogen-stimulated PBL, and mixed lymphocyte cultures (MLC). Using a computer program that superimposes histograms and calculates their differences on the scale of fluorescence intensity, it was possible to quantify the intensity of the response to the mitogenic stimuli. This approach to the study of lymphocyte proliferation offers not only a simpler and faster analysis of DNA synthesis than the method of 3H-thymidine incorporation, but it also allows for the analysis of other FCM parameters, such as forward and 90 degrees light scatter and double fluorescence labelling of PBL nuclei.

Autoimmune thyroid disease: immunological, pathological, and clinical aspects

Autoimmune thyroiditis, most notably Hashimoto's thyroiditis, appears to be increasing in prevalence and is now more easily detected by sensitive laboratory tests and more invasive procedures such as fine needle aspiration. During the last decade, marked progress has been made in the understanding of these diseases. There is a greater awareness of the interaction between the humoral and cell-mediated arms of the immune system in autoimmune thyroiditis. Recent studies implicate a subpopulation of suppressor T lymphocytes which have an antigen-specific defect, resulting in their suboptimal interaction with the helper T lymphocytes and subsequent autoimmune manifestations. There is some evidence that thyroid epithelial cells which inappropriately express HLA-DR may enhance presentation of thyroid antigens to the immune system, possibly significant in the initiation or enhancement of the autoimmune response. The presence of various antithyroid autoantibodies allows the use of laboratory assays to confirm the clinical diagnosis and predict the results of treatment. There appears to be predisposing genetic factors in the development of autoimmune thyroiditis, with some geographical and racial differences. Environmental factors, most notably dietary intake of iodine, have also been implicated in the pathogenesis of Hashimoto's thyroiditis. Several animal models have been developed addressing such issues. Ongoing studies in the areas of postpartum thyroiditis and childhood thyroiditis are helpful in clarifying their relationship with Hashimoto's thyroiditis. Graves' disease and postpartum thyroiditis are being investigated as possible causes of postpartum depression. The association of Hashimoto's thyroiditis and carcinoma of the thyroid gland is still controversial, but its relationship with malignant lymphoma is now well accepted. Thus, although the pathogenesis of autoimmune thyroiditis remains elusive, there has been significant refinement of the clinical diagnosis, and immunological abnormalities of specific intrathyroidal lymphocytes have been identified. Hopefully, these new areas of knowledge will assist in the treatment of these diseases and in the prevention of the development of malignant lymphomas of the thyroid gland.

B lymphocytes respond specifically to phytohaemagglutinin after liposome-dependent transfer of purified phytohaemagglutinin receptors

Phytohaemagglutinin (PHA) receptor glycoproteins purified by affinity chromatography from porcine splenic lymphocytes, were reconstituted into vesicles made of phosphatidylcholine and phosphatidylserine, concomitantly with Sendai virus fusogenic proteins HN and F. The vesicles were used as a vehicle to insert the PHA receptor glycoproteins into a highly enriched population of porcine B lymphocytes. Fluorescence analyses showed that 52 +/- 2% of the reconstituted B cells had incorporated the lectin receptors. The modified B lymphocytes were assayed for their response (tritiated thymidine incorporation into nucleic acids) to PHA, concanavalin A (Con A), or to lipopolysaccharide (LPS). The results showed that porcine B cells fused with vesicles containing only viral fusogenic proteins failed to respond to either PHA or Con A. Tritiated thymidine incorporation was similar to background values. The cells did, however, respond to LPS with values of label incorporation similar to those observed in the case of pre-fused B lymphocytes. When purified B lymphocytes were fused with vesicles containing PHA receptors and viral fusogenic proteins, assays of thymidine incorporation showed a statistically significant (P less than 0.001) and specific response of the modified cells to PHA stimulation. Reconstituted cells cultured in the presence of PHA incorporated approximately nine times more radioactive label than pre-fused cells or cells fused with vesicles containing only fusogenic viral proteins. In marked contrast, reconstituted B lymphocytes did not show any significant label incorporation above background level in response to Con A, but they retained their ability to respond to LPS. Our findings suggest that B lymphocytes can be made to respond specifically to PHA by insertion of appropriate lymphocyte-derived receptors.

Immunoglobulin synthesis in myelodysplastic syndromes: normal B-cell and immunoregulatory T-cell functions

Peripheral blood cells from patients with myelodysplastic syndromes were assayed for B-cell and immunoregulatory T-cell functions. The B/T cell ratio in myelodysplastic patients (n = 11) was significantly higher than in controls (n = 12). These patients had a reduction in total T-cell (OKT3+) frequency and in T-cell subset (OKT4+/OKT8+) ratios. The response of patients' cells to both pokeweed mitogen (PWM) and phytohemagglutinin (PHA) was reduced, but patients' B cells responded normally to stimulation with Staphylococcus aureus Cowan (SAC). The levels of IgG and IgM detected in 7-day culture supernatants of PWM-stimulated patient and control cells were similar. Normal B-cell and immunoregulatory T-cell functions were subsequently demonstrated in allogeneic co-culture combinations of enriched T and B cells from patients and controls. The data presented indicate that the frequent infections of myelodysplastic patients are not causally related to impaired humoral mechanisms. The data also favor the possibility that the stem cell disorder in these syndromes is functionally expressed at a subsequent stage to the lymphoid differentiation pathway.

Optimized density gradient separation of leukocyte fractions from whole blood by adjustment of osmolarity

Some of the compounds used for density gradient separation of blood cells have high osmolarities at the concentrations needed to create the required specific densities. Several mixed media use a combination of hyperosmolar shrinkage and red cell aggregation to improve cell separation. Due to the characteristics of Percoll density gradient medium the density and osmolarity of the gradient can be controlled separately. In the present study, Percoll gradients were used to determine the buoyant densities of different human blood cells at the osmolarities 300 mosM, 350 mosM and 400 mosM. Cell volumes were measured at the same osmolarities using a Coulter counter with channelyzer. As expected, the cell buoyant densities increased and the cell volumes decreased at the higher osmolarities used. There were, however, quantitative differences between the cells with respect to the effects of an increased osmolarity, making a 350 mosM density gradient the most effective in separating mononuclear leukocytes from polymorphonuclear leukocytes. A 400 mosM gradient offered the best possibilities to separate red blood cells from polymorphonuclear leukocytes. A one-step centrifugation procedure, based on these principles, is presented. This procedure makes possible the simultaneous purification of mononuclear leukocytes and polymorphonuclear leukocytes, suitable for functional assays.

Measurement of single-cell DNA synthesis by pokeweed mitogen-stimulated mononuclear cells with combined light and scanning electron microscopy

The response of peripheral blood mononuclear cells to pokeweed mitogen (PWM) stimulation was investigated with combined light (LM) and scanning electron microscopy (SEM). The DNA content of the nucleus of a cell (measured by fluorescence) was compared directly with the diameter and morphological features (by SEM). It was found that upon PWM stimulation lymphocytes transform into blast cells without measurable increase of diploid DNA content (4C) were not seen. The results of DNA fluorescence measurements were comparable with [3H]thymidine uptake profiles, both having peak values on Days 4 and 5 after the start of stimulation. Lymphocyte-enriched populations stimulated by PWM showed a small but distinct population of cells with a diameter of approximately 4-5 micrometers and having a tetraploid DNA content on Days 3, 4 and 5 after the start of stimulation. This reflects the cells' ability to divide in response to mitogen stimulation. SEM showed no characteristic cell-surface morphology for blast cells with increasing DNA content.

Effects of anti-IgM on mitogen-induced proliferation of human B-lymphocyte malignancies

Therapeutic trials of anti-immunoglobulin antibody have produced a wide range of responses in attempts to control the growth of human B lymphoid neoplasms. This variability might reflect differences in intrinsic functional characteristics of malignant B lymphocytes that determine susceptibility to anti-immunoglobulin-mediated regulation of growth. To characterize B-lymphocyte malignancies, tissue samples from 24 patients were studied during short-term culture in vitro. Malignant B lymphocytes were stimulated to proliferate by the T-independent mitogens lipopolysaccharide, cytochalasin B, and Staphylococcus aureus that bears protein A. The effects of monoclonal mouse anti-human IgM on mitogen-induced malignant lymphocyte proliferation were then assessed. Mitogen-induced responses of malignant lymphocytes from three patients were abrogated by 2 micrograms/ml monoclonal anti-human IgM. Proliferation was also abrogated by polyclonal goat anti-IgM antiserum but proliferative responses were not affected by control monoclonal antibody. Further study showed that anti-immunoglobulin-mediated inhibition of proliferation was not dependent on Fc-determined interactions, nor was it dependent on the presence of T lymphocytes. These results indicate that a subset of human B-lymphocyte malignancies are susceptible to inhibition of proliferation mediated by anti-IgM.