Functional heterogeneities among concanavalin A-activated OKT4+ and OKT8+ cells by using autologous erythrocyte rosette technique

In Vivo Acute Toxicity and Immunomodulation Assessment of a Novel Nutraceutical in Mice

Achieving and maintaining a well-balanced immune system has righteously become an insightful task for the general population and an even more fundamental goal for those affected by immune-related diseases. Since our immune functions are indispensable in defending the body against pathogens, diseases and other external attacks, while playing a vital role in maintaining health and modulating the immune response, we require an on-point grasp of their shortcoming as a foundation for the development of functional foods and novel nutraceuticals. Seeing that immunoceuticals are considered effective in improving immune functions and reducing the incidence of immunological disorders, the main focus of this study was to assess the immunomodulatory properties and possible acute toxicity of a novel nutraceutical with active substances of natural origin on C57BL/6 mice for 21 days. We evaluated the potential hazards (microbial contamination and heavy metals) of the novel nutraceutical and addressed the acute toxicity according to OECD guidelines of a 2000 mg/kg dose on mice for 21 days. The immunomodulatory effect was assessed at three concentrations (50 mg/kg, 100 mg/kg and 200 mg/kg) by determining body and organ indexes through a leukocyte analysis; flow cytometry immunophenotyping of lymphocytes populations and their subpopulations (T lymphocytes (LyCD3+), cytotoxic suppressor T lymphocytes (CD3+CD8+), helper T lymphocytes (CD3+CD4+), B lymphocytes (CD3-CD19+) and NK cells (CD3-NK1.1.+); and the expression of the CD69 activation marker. The results obtained for the novel nutraceutical referred to as ImunoBoost indicated no acute toxicity, an increased number of lymphocytes and the stimulation of lymphocyte activation and proliferation, demonstrating its immunomodulatory effect. The safe human consumption dose was established at 30 mg/day.

Concanavalin A directly stimulates bone-resorbing activity of osteoclasts and their gene expression of cathepsin K/OC-2

Concanavalin A (Con A), a plant lectin that recognizes cell-surface glycoproteins, up-regulates osteoclastic bone-resorbing activity of cultured isolated rabbit pure osteoclasts as well as unfractionated bone cells. The effect of Con A was blocked by alpha-methyl mannopyranoside. Several Con A-binding proteins were detected in the plasma membranes from osteoclasts. Furthermore, Con A increased the levels of transcripts of cathepsin K/OC-2, one of the proteases responsible for osteoclastic bone-resorbing activity. These results indicate that Con A directly enhances the function of osteoclasts by the association with surface glycoproteins of osteoclasts.

Induction of a subpopulation of suppressor cells by a single blood transfusion

Blood transfusion induces immunosuppression by a mechanism which is probably multifactorial and, in large part, obscure. In this study cellular immune suppression was examined in patients with end-stage renal disease (ESRD) following a single blood transfusion (BT). OKT8+ cells proliferated within four hours, their count increasing significantly, and reached their peak after four days. Since OKT4+ cells tended to decrease, the OKT4/OKT8 ratio declined significantly from the fourth day. Evidence in support of the above results is offered in studies on ability of concanavalin A reagent (ConA)-activated T cells to form autorosettes with human red blood cells (RBC); these T cells have been shown to function as suppressor effector cells. Autorosetting cells (RFC) proliferated in a similar pattern to OKT8+ cells. Moreover, the percentage of rise at one and two weeks of OKT8+ and RFC correlated directly, suggesting that the proliferating OKT8+ cells are in large part a subset of suppressor cells. Functional studies were performed to establish the suppressor activity of T cells before and at various times after blood transfusion. A significant increase in T cell ConA-induced suppressor activity was found one week after BT, peaking at two weeks following BT. Monocytes increased significantly from day 4 following BT, but prostaglandin E2 (PGE2) started to rise immediately, peaking at day 4. PGE2 might induce suppression by induction of suppressor cells or by direct suppression of interleukin-2. Both monocytes and suppressor cells respond immediately, but they probably induce suppression most effectively four days or more after BT.

Alterations in serum cortisol, CD4+CD8+ lymphocyte sub-population ration and T cell mediated suppression of immune responses in the malnutrition of anorexia nervosa

Serum cortisol and T lymphocyte sub-populations (CD3+, 4+ and 8+) were studied in 22 consecutively admitted patients with anorexia nervosa (AN) who had a mean weight loss of 30%. In addition Concanavalin A (Con A) mitogen induced T cell suppression of lymphocyte response to PPD (purified protein derivative of tuberculin antigen) was analysed. Increased serum cortisol concentrations were found in the AN-patients compared to the control group, with mean levels 654 and 418 nmol/l respectively. The relative numbers of CD4+ lymphocytes (mean 36.2%) and the CD4+ CD8+ ratio (mean 1.54) were significantly reduced (p < 0.05) in the AN-patients compared to the control group (mean 41.6% and 2.14 respectively). T cell mediated, Con A induced suppression of lymphocyte response to PPD was increased in AN-patients compared to the control group with low (1mug/ml) Con A concentration, but unchanged with high (5 mug/ml) Con A concentration. There was no correlation between serum cortisol concentrations and the numbers of T lymphocyte subpopulations or T cell suppressor activity. In contrast, a highly significant correlation existed between serum cortisol and the duration of AN (p < 0.002), but not with relative weight loss or anthropometric variables: triceps skin-fold (TSF) and arm muscle circumference (AMC). Immunological variables were not correlated with duration of disease. Thus, immunological alterations of the T cell system are detectable in AN, but are subtle and their clinical importance is not well known.

Effect of hemodialysis on T lymphocyte subsets, con-A-activated suppressor cell activity, and interleukin-2 receptor expression on lymphocytes in chronic uremic patients

Effect of hemodialysis (HD) on some indices of immune response was studied in nine chronic uremics. Total lymphocyte, OKT4+, and OKT8+ cell numbers significantly decreased during the first 20 min of HD, and they were decreased till the third hour of the procedure, whereas the OKT4+/OKT8+ cell number ratio did not change significantly. Before HD, Con-A--activated suppressor cells exerted a stimulatory action on autologous responder cells measured in two-step culture. During HD, Con-A-activated suppressor cell activity transiently appeared, with its peak at 60 min after the start of HD. It was accompanied by a transient rise in lymphocyte count with spontaneous interleukin-2 (IL-2) receptor expression, whereas the number of cells expressing IL-2 receptor following phytohemaglutinin (PHA) stimulation was progressively decreased during HD. A significant correlation was found between the increment of Con-A-activated suppressor cell activity and the increment of spontaneous IL-2 receptor expression on lymphocytes during one single blood flow through the dialyzer. The results supply further evidence that HD may impose additional disturbances on immune regulation in chronic uremics.

Two distinct subsets of patients with systemic lupus erythematosus

This study was undertaken to examine the levels and function of peripheral blood immunoregulatory T cell subpopulations in systemic lupus erythematosus (SLE). T cell subpopulations can be distinguished by the T cell differentiation antigens CD4 (recognized by the monoclonal antibodies OKT4 or Leu3) and CD8 (recognized by the monoclonal antibodies OKT8 or Leu2). All SLE patients tested had normal percentages of CD8 cells in their peripheral blood. The SLE patients, however, fell into two groups based on their CD4 cell numbers. Fifty-five percent of the SLE patients had normal levels of CD4 cells (Group A) and therefore normal CD4/CD8 cell ratios, whereas 45% of the SLE patient population had markedly depressed CD4 cell levels (Group B) and significantly low CD4/CD8 cell ratios. T cells from normal donors and SLE patients were further examined for their ability to stimulate allogeneic normal B/M phi cells to secrete IgM in the presence of pokeweed mitogen (PWM). Utilizing this assay system two forms of immunosuppression were observed: (1) that mediated by high concentrations of purified CD4 cells and (2) that mediated by CD8 cells. High concentrations of purified CD4 cells, added to a constant number of allogeneic normal B/M phi cells, suppressed PWM-stimulated IgM synthesis. Group B SLE patients, with significantly low CD4 cell numbers, had defective CD4 cell-mediated suppression which was concentration dependent. This result was confirmed in a study using identical twins discordant for SLE. In this case CD4 cells from the SLE twin did not induce immunosuppression at a high concentration of CD4 cells whereas similar concentrations of CD4 cells from the normal twin resulted in suppression. SLE patients (Group A) with normal levels of CD4 cells had normally immunosuppressive CD4 cells. Suppression mediated by CD8 cells was demonstrated by the fact that removal of CD8 cells resulted in enhanced IgM synthesis induced by the remaining CD4 cells. Although all the SLE patients in this study had normal peripheral blood levels of CD8 cells, SLE Group A patients had defective CD8 cell suppression whereas CD8 function appeared to be normal in Group B patients. These results suggest that in SLE patients with depressed CD4 cell numbers (Group B) there is a corresponding defect in CD4 cell function. We demonstrate that in SLE Group B patients, defective suppression is due to a subset of T cells that bear the CD4 antigen. The SLE patient population (Group A) with normal CD4/CD8 ratios and normally functioning CD4 cells, however, appear to have normal CD4 cell-mediated suppression but defective CD8 suppressor cell function.

Human alveolar macrophage suppression of lymphocyte proliferation. Accessory characteristics for the generation and functional expression of con A-induced suppressor cells

Human alveolar macrophages (AM) provide less accessory support for mitogen- and antigen-stimulated lymphocyte proliferation than do autologous blood-derived macrophages (BM). This is at least in part due to suppression mediated by AM, but the mechanism of such suppression is not understood. To determine whether AM-mediated suppression is related to AM interaction with suppressor lymphocytes (Ts), we examined the accessory cell function of both AM and BM for the generation and functional expression of Ts induced by concanavalin A (Con A). The data indicate that human AM are equivalent to BM for the generation of Con A-induced Ts, but AM mediate less suppression of Con A-induced Ts, once generated, than do BM. Addition of indomethacin did not increase lymphocyte proliferation when AM served as accessory cells. Supernatant fluids of Con A-exposed AM promoted greater proliferation of human T-lymphocytes and mouse thymocytes than did supernatant fluids from Con A-exposed BM. Interleukin-1 inhibitor activity was not detected in the supernatant fluids. These observations make it unlikely that soluble factors alone account for AM-mediated suppression. Thus, at least for the Con A-induced Ts system, AM do not mediate suppression either via better generation or greater functional expression of suppressor cells relative to BM. The paradoxically greater proliferation of lymphocytes stimulated by the supernatant fluids of Con A-exposed AM raises the possibility that suppression of Con A-stimulated lymphocyte proliferation observed when AM serve as the accessory cells in primary culture may be related to AM secretion of a molecule with IL-1-like activity.

Alternative pathway of complement activation by stimulated T lymphocytes. I. Binding of C3 fragments

Human blood lymphocytes cultured for 3 days with concanavalin A (Con A), phytohemagglutinin or pokeweed mitogen, in mixed lymphocyte culture with added interleukin 2 and stimulated by a lymphoblastoid cell line were found to activate and bind C3 molecules when exposed to human serum. The split products of C3 were detected in the supernatants and on the surface of the activated cells. The surface-attached C3 fragment on the Con A blast was identified as C3b by immune adherence i.e. binding of CR1 carrying human erythrocytes. In the Con A-stimulated population the majority of cells that activated and bound C3 were CD3 and Fc gamma receptor (CD16)-positive but complement receptor-negative blasts. In this cell subset both CD4 and CD8-positive cells were detected but their frequency suggested that a proportion of them carried both markers.

The immune system during the pre-cancer and the early cancer period. IL-2 production by PBL from post-menopausal women with and without endometrial carcinoma

We report on alterations in IL-2 production and cell proliferation following PHA stimulation of peripheral blood lymphocytes (PBL) from stage-I endometrial carcinoma (EC) patients, and on mechanisms involved in these alterations. Our study includes 3 groups: EC patients, post-menopausal women at high risk of developing EC, and age-matched healthy women. IL-2 production was markedly lower in most EC patients than in healthy controls. Varying levels of IL-2 were produced by PBL from women in the high-risk group. The proliferative response of PBL to PHA appeared to correlate with levels of IL-2 production. Our results suggest that macrophages are involved, in part, in the modulation of T-cell functions of EC patients.

Processing of concanavalin A-receptor complexes by rat osteoclasts in vitro

The osteoclast is a large multinucleate cell that is widely accepted as the primary effector cell responsible for normal bone resorption. In a previous study, we demonstrated that concanavalin A (con A) has a dose-dependent biphasic effect on the bone-resorbing capacity of osteoclasts, using a 45Ca bone-organ culture system; bone resorption was stimulated at low concentrations and inhibited at high concentrations. The mitogenic property of con A in lymphocyte cultures is well documented; therefore con A has been used extensively to study the manner in which lymphocytes and other mononuclear cells process the cell-bound lectin. In this study, we have investigated the processing of con A-receptor complexes by osteoclasts in culture, using con A-FITC to evaluate the redistribution of cell-bound con A via epifluorescence microscopy and using con A-ferritin to determine whether the lectin receptor complexes are internalized. The osteoclasts were obtained from the long bones of newborn rats and allowed to attach to glass coverslips at 37 degrees C. Following attachment, the nonadherent cells were removed by rinsing. The adherent osteoclasts were preincubated in 50 micrograms/ml con A-FITC or con A-ferritin at 4 degrees C for 10 min, washed to remove unbound con A, and incubated at 37 degrees C for 15 or 30 min in the absence of con A. Positive controls were fixed immediately after preincubation at 4 degrees C; negative controls were preincubated in con A-FITC and alpha-methyl mannoside, the haptenic inhibitor of con A binding. The results demonstrate that redistribution and endocytosis of con A-receptor complexes occurs within 30 min. These findings confirm the hypothesis that cell-bound con A can alter the structure and activity of osteoclast membrane components in a manner similar to that observed in mononuclear cell cultures. The internalization of con A may be important in altering osteoclastic activity by mediating intracellular mechanisms involved in the bone-resorbing process.

Analysis of interleukin-2 activity in patients with Behçet's disease. Ability of T cells to produce and respond to interleukin-2

We examined interleukin-2 (IL-2) activity in patients with Behçet's disease. T cells from all patients with Behçet's disease were able to produce normal levels of IL-2 in response to phytohemagglutinin; however, responsiveness to IL-2 was impaired in their concanavalin A-activated lymphoblasts. This defect was due to decreased numbers of cells bearing IL-2 receptors in patients with early active disease; in patients with chronic active or with inactive disease, there was a decrease in density of IL-2 receptors on T cells bearing these receptors. Unresponsiveness of T cells to IL-2 may thus contribute to immunologic aberrations in Behçet's disease.

Abnormal B cell function in patients with Behçet's disease

We evaluated B lymphocyte function in 23 patients with Behçet's disease at various stages. The patients with active disease, but not those with inactive disease, were found to have elevated numbers of cells spontaneously secreting immunoglobulin and a decreased B cell response to the T cell-independent B cell mitogen, Staphylococcus aureus Cowan 1. Moreover, B cells from almost all patients with Behçet's disease were unresponsive to the T cell-dependent polyclonal activator, pokeweed mitogen. These results indicate that B cell abnormalities, including some which are associated with disease activity, could be involved in the pathogenesis of Behçet's disease.

Implications for the role of cognate interactions in in vitro human B cell activation by Staphylococcus aureus Cowan I and pokeweed mitogen

Human B cell-triggering mechanisms were investigated using the polyclonal activators Staphylococcus aureus Cowan I (SAC) and pokeweed mitogen (PWM). When the cultures of B cells, T cells, and monocytes were stimulated for 5 d by SAC or PWM, B cells could be activated by both mitogens to proliferate and secrete Ig. Even when T cells were substituted by T cell-derived soluble factors, SAC-stimulated B cells could differentiate into Ig-secreting cells. In contrast, interactions of B and T cells for at least the first 6 h of culture were necessary for the B cell triggering by PWM. Experiments that allow a more precise delineation of the B cell-triggering mechanisms by PWM demonstrated that interactions of B cells with T4+ but not T8+ cells are required for the B cell triggering; anti-Ia or anti-T4 antibody can block this triggering; in contrast, anti-T3 or anti-T8 antibody do not exert any effects on the B cell triggering. However, all these monoclonal antibodies could not modulate the ability of B cells that had been already activated by PWM to respond to T cell-derived factors. These data suggest that SAC can directly activate B cells, while cognate interactions between Ia-like antigens on B cells and T4+ cells are essential for B cell triggering by PWM. Furthermore, once B cells are triggered, they will proliferate, differentiate, and secrete Ig in response to T cell-derived factors; Ia-like antigens or T cell differentiation antigens may not be involved in the processes in this cascade.

Changes in T lymphocyte subsets following injury. Assessment by flow cytometry and relationship to sepsis

The increased susceptibility of severely injured patients to infection and death from sepsis has been attributed to abnormalities in cell-mediated immunity. The authors therefore assessed the relative number of peripheral blood T helper cells and T suppressor/cytotoxic cells and total T lymphocytes identified by the monoclonal antibodies (McA) OKT4, OKT8, and OKT3, respectively, in 25 patients with burns from 5 to 85% total body surface area (TBSA) (mean: 40%) and 21 patients with nonthermal injuries (mean Injury Severity Score (ISS): 21.4). Patients were compared to 21 healthy controls. Cells reacting with the McA were detected by flow cytometry, which enabled the examination of a population of cells the size of T lymphocytes, excluding larger contaminating cells that might bind the McA. Patients with burns of 30% TBSA or greater had a significant reduction (p less than or equal to 0.05) in OKT3+ cells up to 50 days post-burn. Both septic and nonseptic burn patients had reduced numbers of OKT3+ cells, as did patients after nonthermal injury, suggesting that this reduction was due to the injury itself. Patients with smaller burns (less than 30% TBSA) as a group did not have reduced OKT4+ cells, whereas those with larger burns showed significant reductions in OKT4+ cells (P less than or equal to 0.05) at 0 to 5, 6 to 10, 11 to 20, 21 to 30, and 41 to 50 days post-burn. Seven burn patients who became septic 10 days post-burn or later had significantly lower OKT4+ cells within 10 days of injury (mean: 33.75% +/- 7.4 SEM) than 10 patients who remained free of sepsis (mean: 42.2% +/- 5.4, p = 0.004). Patients with uncomplicated nonthermal injuries failed to show any significant reduction in OKT4+ cells. Following thermal injury, a reduction in OKT8+ cells was observed up to 10 days in patients with burns less than 30% TBSA, and up to 20 days in patients with larger burns. In both groups, at no time were increased OKT8+ cells found to correlate with clinical events. In patients with nonthermal injury, OKT8+ cells generally remained near the normal range.

Human autologous rosette-forming cells. IV. Functional role in T-cell activation

Human autorosette-forming cells (auto-RFC), which represent a T4/leu 3a+ cell subset, were investigated for their functional role in T-cell activation. Peripheral blood lymphocytes from healthy subjects either remained unfractionated or were separated into recovered or depleted auto-RFC populations. The phytohemagglutinin P stimulation of these three cell suspensions induced normal levels of proliferation, whereas the pokeweed mitogen activation was significantly decreased in the auto-RFC-depleted population compared to the auto-RFC-recovered subset or unfractionated cells. All three cell suspensions produced IL-2 in response to PHA stimulation. However the levels of lymphokine released were significantly lower in the recovered auto-RFC fraction than in the depleted auto-RFC. After activation, using anti-Tac antibodies, the synthesis of IL-2 receptors was evidenced in all the cell fractions regardless of the presence or absence of auto-RFC. In addition, both auto-RFC absorbed IL-2 activity from a reference supernatant. Taken together, these data suggest that auto-RFC can be expanded by T-cell mitogens, and that once activated, they express IL-2 receptors, but represent a minor source of IL-2 production.

OKT4+ and OKT8+ T lymphocytes produce soluble factors that can modulate growth and differentiation of human B cells

The human T cell subset(s) responsible for the production of soluble factors that can modulate B cell growth and B cell differentiation was investigated in the present study. For this purpose, highly purified OKT4+ and OKT8+ lymphocytes were stimulated with phytohaemagglutinin and phorbol myristate acetate. Subsequently, culture supernatants were analysed for B cell growth factor (BCGF) activity and B cell differentiation factor (BCDF) activity in the following systems: 1) maintenance of a proliferative state of Staphylococcus aureus of strain Cowan I (SAC)-stimulated B cells and 2) induction of plaque-forming cell responses of SAC-stimulated B cells. Mitogenic stimulation led to production of equivalent amounts of either BCGF activity or BCDF activity from both of the OKT4+ and OKT8+ subsets. These findings may provide a basis for further studies of the molecular mechanisms as well as cellular interactions involved in human B cell activation, proliferation and differentiation.

Effect of theophylline on the proportion and function of T-suppressor cells in asthmatic children

T-cell subpopulations and their function were studied in asthmatic children with or without theophylline therapy. A decreased proportion and function of theophylline-sensitive T-suppressor cells was found in fresh peripheral blood of asthmatic children. Following peripheral blood mononuclear cells (PBMC) incubation in theophylline-free medium, the proportion of theophylline-sensitive T-cells in asthmatic children treated with theophylline was elevated to normal values. However, their suppressive effect on control lymphocyte proliferation was unchanged.

Subset specificity of antilymphocyte antibodies in systemic lupus erythematosus. Preferential reactivity with cells bearing the T4 and autologous erythrocyte receptor phenotypes

The relative specificity of systemic lupus erythematosus antilymphocyte antibodies for T cell subsets bearing the OKT4, OKT8, or autologous erythrocyte rosette (A-RFC) markers was examined in complement-dependent microcytotoxicity assays and by indirect immunofluorescence. Target cells included normal OKT4+ or OKT8+ T cell clones established from mitogen-activated blasts, resting or phytohemagglutinin-activated peripheral T cells highly enriched for OKT4+ cells or OKT8+ cells, and A-RFC+ and A-RFC- populations. In the majority of sera, cytotoxicity for T4+ cells was greater than that for T8+ cells regardless of cellular activation status. Overall cytotoxicity was considerably higher for activated cells, however, especially when warm assay temperatures were used. A-RFC+ targets were more reactive than nonrosetting T cells, and this was associated with strikingly higher relative fluorescence intensity of IgM staining. Despite these consistent differences in relative cytotoxicity or staining, antibody titers against all cell types were strongly correlated in individual sera. Absorption experiments failed to demonstrate distinct antibody specificities for T4+ and A-RFC+ cells. These data suggest that the major determinant of cytotoxic reactivity may be a single or limited number of surface antigens common to all T cells. Superimposed on this dominant system(s) is a special reactivity with certain distinct subsets and with activated T cells generally.

In vitro selective effect of melphalan on human T-cell populations

In vitro treatment with 2 micrograms/2 X 10(6) cells melphalan (L-PAM: L-phenylalanine mustard) significantly decreased the total number of T lymphocytes from peripheral blood (PBL) of healthy human donors and of the OKT4 population (precursor suppressor/helper/inducer) T cells as defined by monoclonal antibodies OKT3 and OKT4, respectively. No changes in the OKT+8 lymphocyte population (cytotoxic/mature suppressor cells) were observed following the same treatment. Preincubation of PBL with L-PAM at concentrations that do not affect the rate of DNA synthesis in PHA-stimulated lymphocytes inhibited the generation of T suppressor lymphocytes by ConA, as shown by their effect on PHA stimulation. Treatment of allogeneic PBL with L-PAM had no effect on mature suppressor T cells already induced by ConA, as shown by incubation of PBL with L-PAM after incubation with ConA.