Con A-induced Suppressor Cell Research Articles

Immunomodulating anticancer alkylating drugs: targets and mechanisms of activity.

CY and L-PAM potentiated specific anti-tumor response in addition to their killing effect. The immunomodulating effect of a low dose of either CY or L-PAM was expressed in mice bearing large s.c. MOPC-315 plasmacytoma tumors. Cured mice were resistant to a challenge dose of the syngeneic tumor and their spleens contained specific cytotoxic T cells. Induction of specific anti-tumor response by a low dose of alkylating drugs was due to expression of "latent anti-tumor" capability. This fitted with the conception that "suppressed concomitant immunity" occurring in tumor-bearing animals can be activated. The immunomodulating activity of alkylating drugs was related to enhancement of T-cell functions:impairment of suppressor T-cell activity,enhancement of effector T-cell activity and increase in production of cytokines at the tumor site. The target tumor killing activity of a low dose alkylating drug was dissociated from its immunomodulating activity by treating mice bearing a tumor resistant to an alkylating drug. A low dose of CY had an immunomodulating effect in human cancer such as reduction of ConA-induced suppressor cell activity in melanoma, some improvement in addition to use of melanoma vaccine, and potentiation of DTH in cancer patients. The immunomodulating effect of alkylating drugs suggest that their use might be beneficial not only for killing tumor cells but also for promoting specific anti-tumor immune response.

Prednisone and plasma exchange improve suppressor cell function in chronic inflammatory demyelinating polyneuropathy

We have recently demonstrated that ConA-induced suppressor cell function is defective in chronic inflammatory demyelinating polyneuropathy (CIDP). To assess whether this defect plays a role in disease activity and its reversal is important in recovery, we studied modifications of ConA-induced suppressor cell function induced by prednisone and plasma exchange in 20 patients with CIDP. We found a significant increase towards normal of ConA-induced suppressor cell function after treatment in concurrence with clinical improvement. Induction of suppression, presumably through favorable modifications of the cytokine network or other humoral mediators, might be one, among others, of the mechanisms through which prednisone and plasma exchange are effective in CIDP.

Effects of an anti-IL-10 monoclonal antibody on rIFN β-1b-mediated immune modulation. Relevance to multiple sclerosis

The mechanism of action of recombinant IFN β 1b (IFN β-1b), as a therapy for multiple sclerosis (MS), is still unknown but may result from the enhancement of ConA-induced suppressor cell function and the inhibition of IFN γ secretion by lymphocytes. We previously demonstrated that IFN β-1b stimulated modest amounts of IL-10 secretion by monocytes and IL-10 activity, as cytokine synthesis inhibitory factor, was normal in MS. To determine whether IL-10 plays a role in IFN β-1b modulation of immune function in MS, we studied ConA-induced suppressor cell function and IFN γ production in presence of IFN β-1b and an anti-IL-10 monoclonal antibody (mAb). Anti-IL-10 mAb significantly reduced the effect of IFN β-1b on ConA-induced suppressor cell function and IFN γ production in healthy subjects; MS patients showed a trend of inhibition. We hypothesized that IL-10 may play a role in mediating the effects of IFN β-1b on suppressor cell function and IFN γ production but suppressor molecules other than IL-10 could be also involved.

Modulation of suppressor cell activities by cyclophosphamide in breast cancer patients.

We investigated the immunomodulatory effect of cyclophosphamide on the induction of suppressor cell activities in peripheral blood lymphocytes. The sera from advanced breast cancer patients as well as concanavalin-A (Con-A) induced suppressor cell activities in lymphocytes from healthy volunteers. Pretreatment of these lymphocytes, including CD4+ T cells with 4-hydroperoxycyclophosphamide (4-HC), an active form of cyclophosphamide, abrogated the induction of suppressor cell activities by either cancer sera or Con-A. A decrease in CD4+CD45RA+ suppressor/inducer T cells and reduction of Con-A induced suppressor cell activities were observed in breast cancer patients with metastases that were treated with cyclophosphamide (CPM). These results suggest that cyclophosphamide may modulate the immune responses of breast cancer patients by interference with suppressor/inducer T cells.

Concanavalin a-induced suppressor cell activity in patients with renal cell carcinoma

Concanavalin A (Con A)-induced suppressor cell activity against the proliferative response of autologous lymphocytes to phytohemagglutinin was examined in peripheral blood lymphocytes derived from 12 normal control subjects and 25 patients with renal cell carcinoma (RCC). The Con A-induced suppressor cell activity in patients with RCC (23.4 +/- 21.4%) was significantly higher than that in control subjects (9.7 +/- 10.7%, P less than 0.05). No significant difference between the degree of suppressor cell activity and stage of disease, grade of malignancy, or cell type was found, although the suppressor activity in patients with tumor microscopically infiltrated by lymphocytes was significantly higher than in patients without lymphocyte-infiltration into the tumor (P less than 0.05). Furthermore, compared with control subjects, Con A-induced suppressor activity in patients with high stage and in those with lymphocyte infiltration into the tumor was significantly higher (P less than 0.05 and P less than 0.01, respectively). In conclusion, because patients with RCC have high suppressor cell activity, abrogation of this activity may be necessary to treat the RCC.

Con A-induced suppressor cell function depends on the activation of the CD4 +CD45RA inducer T cell subpopulation

Human T cells incubated for 48 hr with Con A suppress B cell Ig production. We sought to define the interactions between CD4 + T cells and CD8 + T cells in the generation of suppressor cell activity following Con A stimulation. Con A-activated CD4 + inducer T cells suppressed Ig production in autologous cocultures of T cells and B cells by 84%, while PHA-activated CD4 + T cells could not. However, Con A-activated CD4 + T cells are not themselves suppressors. When Con A-activated CD4 + T cells were added to coculture of B cells plus T cells depleted of CD8 + T cells, no suppression of Ig production was observed. Furthermore, these Con A-activated CD4 + T cells were able to provide excellent help for Ig production. Therefore, Con A-induced suppressor cell function requires a CD4 + suppressor/inducer acting on a CD8 + suppressor/effector ultimately resulting in the down regulation of B cell Ig synthesis. Human CD4 + inducer T cells can be functionally dissected into helper/inducer or suppressor/inducer T lymphocytes based on their expression of either the CDw29 or CD45RA surface molecules, respectively. Following incubation with Con A the expression of CD45RA on CD4 + T cells increased from 34 to 80% ( P = 0.001) while CDw29 expression was unchanged. Incubating lymphocytes with PHA resulted in a non-specific increase in both CD45RA and CDw29 expression by CD4 + T cells. The increase in CD4 +CD45RA expression was a result of active proliferation by the Con A-stimulated T cells. Suppression of Ig secretion was directly correlated with the enhanced CD45RA expression following Con A activation. We demonstrate that enhanced suppressor/inducer function is unique to Con A stimulation and was not observed following activation by PHA. Furthermore, short-term culture with Con A results in the selective expansion of the CD4 +CD45RA T cell subpopulation.

Enhancement of immune reactivities of regional lymphnodes by oral administration of OK-432 in colon cancer patients

Effect of oral administration of OK-432 on the immune reactivities of regional lymphnode (RNLs) and peripheral blood lymphocytes (PBLs) in colon cancer patients were investigated. Twenty KE of OK-432 was given orally on 7 days prior to the operation, and peripheral blood and regional lymphnodes were collected at the time of operation. As for the immune reactivities of PBLs such as lymphocyte proliferative response to phytohemagglutinin (PHA), natural killer (NK) cell activity and Concanavalin A (Con-A) induced suppressor cell activity, there were no significant differences between patients with oral OK-432 (OK-432 (+) group) and those without OK-432 (OK-432 (-) group). NK cell activity of RLNs was significantly higher in OK-432 (+) group than in OK-432 (-) group. Furthermore, the decline of Con-A induced suppressor cell acivity was found in OK-432 (+) group. T cell subsets in regional lymphnode tissues were identified with the use of monoclonal antibodies and immuneperoxidase technique. Both of Leu-2 a and Leu-7 positive cells distributed more frequently in lymphnodes from OK-432 (+) group than in those from OK-432 (-) group. Thus, these results suggested that immune reactivities of regional lymphnodes were en-hanced by oral administration of OK-432 in colon cancer patients.

Effect of oral colchicine on T cell subsets, monocytes and concanavalin A-induced suppressor cell function in asthmatic patients.

Asthmatic patients have a deficiency of concanavalin A-(Con A) induced suppressor cell function. We tested whether oral colchicine 0.5 mg twice daily for 7 days could correct this immunoregulatory abnormality. Peripheral blood mononuclear cells were incubated with Con A and then suppression of proliferation was measured by coculture of these cells with healthy volunteers' mononuclear cells and phytohaemagglutinin. Sixteen asthmatic patients had significantly (P less than 0.002) decreased Con A-induced suppressor cell function (17.0 +/- 17.2%, mean +/- s.d.) as compared to 13 healthy volunteers (37.9 +/- 14.9%). Oral colchicine significantly (P less than 0.05) increased, though only partially corrected, these 16 asthmatic patients' Con A-induced suppressor cell function (28.1 +/- 14.3%). Asthmatic patients had an increased number of monocytes (691 +/- 289 vs 388 +/- 271/mm3 for normals, P less than 0.01) and a normal number of lymphocytes, Leu 4+ total T cells, Leu 3+ helper/inducer T cells, and Leu 2+ suppressor/cytotoxic T cells as well as a normal Leu 3/Leu 2 ratio. Oral colchicine significantly (P less than 0.005) decreased the number of monocytes (451 +/- 255/mm3) without significantly affecting the number of lymphocytes, Leu 4+, Leu 3+, or Leu 2+ T cells, or the Leu 3/Leu 2 ratio. These results are consistent with the hypothesis that the deficiency of Con A-induced suppressor cell function in asthmatic patients may be due, in part, to an increased number and/or abnormal activity of monocytes. If so, then oral colchicine may have partially corrected the deficiency of Con A-induced suppressor cell function by decreasing the number and/or modulating the activity of monocytes.

Thymosin effects on immunoglobulin synthesis and suppressor T cell activity in normal subjects and patients with primary biliary cirrhosis

Peripheral blood lymphocytes from patients with primary biliary cirrhosis previously have been reported to demonstrate reduced pokeweed mitogen-stimulated immunoglobulin synthesis and diminished function of suppressor T cells. To determine whether thymic hormone preparations reverse these immunologic defects in vitro, the effects of thymosin fraction 5 and thymosin α 1 on immunoglobulin synthesis and concanavalin A-induced suppression of immunoglobulin synthesis were investigated in normal subjects and patients with primary biliary cirrhosis. In normal subjects, no effects of thymosin were observed on unstimulated and pokeweed mitogen-stimulated immunoglobulin synthesis, nor on Con A-induced suppressor cell activity. Lymphocytes from patients with PBC synthesized less IgG and IgM than normals when stimulated by pokeweed mitogen, and this difference was enhanced by both thymosin fraction 5 and thymosin α 1. Con A suppression of immunoglobulin synthesis was abnormal in only one PBC subject so that thymosin effects on impaired suppressor T cell activity could not be tested.

Immunological abnormalities in patient with IgA nephropathy.

T cell immunity and phagocytic activity were studied in the blood of patients with IgA nephropathy in order to clarify their roles in the pathogenesis of IgA nephropathy. The percentages of total T lymphocytes, helper T cell and suppressor T cells were significantly reduced in patients. A significantly elevated helper T cell/suppressor T cell ratio in patients showed a predominant reduction in suppressor T cells. There was a significant relationship between histologic findings and helper T cell/suppressor T cell ratio in patients. Natural Killer (NK) cell activity was significantly reduced but the lymphocyte response after phytohemagglutinin (PHA) stimulation was not in patients. ConA-induced suppressor cell activity was not depressed despite of a decrease in suppressor T cells in patients. Phagocytic activity of polymorphonuclear leucocytes (PMNs) ingesting yeasts was significantly reduced in patients. Also an inverse correlation was found between serum IgA levels and phagocytic activity of PMN. It is concluded that suppressor T cell defects, depressed phagocytic activity and impaired NK cell activity may play a role in the pathogenesis of IgA nephropathy.

Immunological profile in children with minimal change nephrotic syndrome.

Peripheral blood from patients with active stage of minimal change nephrotic syndrome (MCNS) was examined for concanavalin A (ConA)-inducible suppressor T cell activity, proliferative response to phytohemagglutinin (PHA) and in the autologous (AMLR) and allogeneic (MLR) mixed lymphocyte reaction, proportions of T cells with receptors for IgM (Tu) or IgG (T gamma) and the levels of serum immunoglobulin M, G and A. Six of 9 patients with MCNS studies showed deficiency of ConA-induced suppressor cell activity. In the AMLR, only one of 9 patients with MCNS demonstrated depressed proliferative response (p less than 0.05). In the allogeneic MLR, T cells from 5 of 9 patients with MCNS demonstrated poor proliferative response when stimulated with normal control non-T cells. Five of 9 patients with MCNS had depressed proliferative response to PHA. The proportion of total T cells, Tu cells and T gamma cells in the patient group were comparable to healthy control group. Serum IgG was significantly decreased in 7 of 11 patients. This study demonstrates multiple immunological abnormalities in patients with MCNS that might play a role in its pathogenesis.

The effects of thymic epithelial monolayer-conditioned medium on suppressor cell function following chemotherapy in pediatric patients.

Human thymic epithelial monolayer-conditioned medium (TEM-CM) enhanced concanavalin A (ConA)-induced suppressor T-lymphocyte activity in 15 of 17 studies of fractionated light-density bone marrow mononuclear cells (LD-BMMC) obtained from pediatric cancer patients within 7 days of chemotherapy (P less than 0.001). However, TEM-CM depressed ConA-induced suppressor T-lymphocyte activity in 14 of 18 studies of LD-BMMC obtained from patients who had received their chemotherapy 14-21 days previously (P less than 0.05). In studies of LD-BMMC from normal subjects, TEM-CM did not show any significant effect on suppressor cell activity, nor did TEM-CM significantly affect spontaneous suppressor cell activity in patients or normals. The effect of direct culture on thymic epithelial monolayers was equivalent to the effect of TEM-CM in both ConA-induced and spontaneous suppressor cell assays. These data demonstrate thymic factor-mediated changes in suppressor T-cell activity of pediatric cancer patients and suggest a postchemotherapy alteration in the bone marrow population of inducible prethymic T cells.

Bestatin therapy of patients with atopic dermatitis

Ten adult patients with severe atopic dermatitis were treated for three months with estatin, which is a metabolite of Streptomyces olivoreticuli. Bestatin has been shown to increase tumor resistance in mice, augment a variety of immune responses and to reduce the level of IgE in non-atopic healthy persons. During bestatin therapy we were not able to see any clinical change of the atopic dermatitis. No influence was found on the concentration of IgE in serum and the number of eosinophils in blood. The percentage of T lymphocytes and the Con A-induced suppressor cell activity was not changed. (Received June 18, 1983.)

Comparative analysis of the suppression by cord blood mononuclear cells of adult and neonatal lymphocytes

The spontaneous or in vivo generated suppressor cell activity of adult and cord blood has been quantitated and compared in a system that examines the regulation of the T-cell response to mitogen. We confirmed previous findings that spontaneous suppressor cell activity is stronger in cord blood. This is only true, however, in a system that uses adult lymphocytes as responder cells. Cord blood responder cells are significantly more resistant to suppressor signals than are adult cells. Thus, the influence of cord blood suppressor cells on cord blood effector cells is equivalent to that seen in similar cocultures containing only adult cells. Spontaneous suppressor cell activity decreases rapidly among cultured adult cells but remains unaffected in cultures of cord cells for at least 4 days. Suppressor cell activity induced by concanavalin A (Con A) was significantly greater with adult cells. The sum of the spontaneous and Con A-induced suppressor cell activity among both cord and adult mononuclear cells was identical, indicating that the total potential suppressor cell function of the two populations is similar and that assays of spontaneous or Con A-induced suppressor cell activity are likely to be examining the same cell population. These findings strengthen the hypothesis that while fetal immunoregulatory cells may be potent suppressor of maternal (adult) lymphocytes, internal (fetal) balance is maintained by having responder cells relatively resistant to these fetal suppressor cells.

Biphasic changes of the immunological reactivity in the course of experimental lectin-induced arthritis of rabbits

A single injection of Lens culinaris lectin (LcL) into the knee joint cavity of non-sensitized rabbits produces an arthritis with an acute and chronic phase, lasting up to one year. The persistence of the lectin in the joint, related to the strong binding affinity of lectins to glycoproteins of connective tissue structures, and the presence of specific antibodies against LcL in the serum after the intra-articular injection make this model comparable to the antigen-induced arthritis. But in our system these conditions are further modified or amplified by the mitogenic activity of LcL itself. The cell-mediated immunity, studied by mitogenic stimulation of peripheral blood lymphocytes, is characterized by a biphasic change in the course of this experimental arthritis. Hyperresponsiveness to stimulation with LcL and Concanavalin A (Con A), decreased Con A-induced suppressor cell activity, and stimulatory serum factors could be detected in the early phase of inflammation. The late phase of arthritis (8 months after the induction) was characterized by hyporesponsiveness to mitogenic stimulation, normal suppressor cell activity and inhibitory serum factors. In spite of the differences of this experimental arthritis to the human rheumatoid arthritis, concerning mainly the initiation and the lack of systemic manifestation, there are surprising similarities between both, not only in the histopathological feature and the chronicity but also in the cell-mediated immune reactions. Therefore, similar pathogenetic mechanisms for the chronic phase can be suggested.

Immunoregulatory T cell function in patients with primary biliary cirrhosis.

Both concanavalin A (Con A)-induced suppressor cell activity and autologous mixed lymphocyte reaction (AMLR) were significantly decreased in patients with primary biliary cirrhosis (PBC) in comparison with those of healthy subjects (p less than 0.001) and p less than 0.001, respectively). Factors inhibiting lymphocyte transformation by Con A and PHA were demonstrated in sera from a majority of the patients with PBC. In approximately half of these patients, some serum factor(s) also induced a decrease of Con A-induced suppressor cell function of lymphocytes from healthy subjects. These results suggest that patients with PBC have impaired immunoregulatory lymphocyte function which may be related to some factor(s) present in serum.

Impaired conA suppressor cell activity in patients with rheumatoid arthritis shows normalization during fasting.

Normal controls and patients with rheumatoid arthritis (RA) were investigated with respect to quantitative lymphocyte proliferation (LP) after concanavalin-A (conA) activation and to conA-induced suppressor cell activity (conA-SC). Measurements and assessment of RA activity were made at the beginning and end of a 10-day fast. The controls showed depressed (p less than 0.05) LP at the end of the fast, but no change in conA-SC activity. The RA group showed subnormal (p less than 0.05) LP and conA-SC (p less than 0.01) at the beginning of the experiment. After fasting they showed clinical improvement, the LP was not further depressed, and the initially low conA-SC had become normal.

Contrasting effects of prostaglandin E 2 and indomethacin in modulating con A-induced human lymphocyte proliferation and suppressor cell development

Several chronic diseases that are characterized by depressed Con A-induced suppressor cell activity are also noted to exhibit depressed in vitro blastogenic responses to mitogens. We investigated the relationship between these two parameters to determine whether depression of lymphocyte proliferation would result in depressed suppressor cell function. First, a correlation in time was found between the degree of initial Con A-induced lymphocyte proliferation and subsequent suppressor development. Second, mitomycin C treatment of Con A-activated cells while preventing further blast cell proliferation, was found not to prevent their suppressor cell function. Third, inhibition of lymphocyte blastogenesis with physiological concentrations of prostaglandin E 2 was also associated with depressed suppressor cell generation. Finally, enhancement of initial lymphocyte proliferation with indomethacin added in vitro resulted in a significant increase in suppressor cell activity. This enhanced response was nullified in the presence of exogenous prostaglandin E 2. These observations strongly suggest that maturation of lymphocytes into blast cells is an important event in the generation of suppressor cells. In addition, these results suggest that caution be taken in interpreting results of Con A suppressor assays in patients with either depressed in vitro mitogen reactivity or in patients taking nonsteroidal anti-inflammatory drugs.

Abnormal generation of concanavalin A-induced suppressor cell function in human autoimmune hemolytic anemia

Lymphocyte reactivity to the mitogens Con A, PHA, and PWM and the generation of Con A-induced suppressor cells were assessed in 12 patients with autoimmune hemolytic anemia (AIHA) and in 20 normal controls. With suboptimal doses of Con A and PHA most patients (9 and 8 out of 12, respectively) gave a response above normal control values. However, no significant difference was observed when optimal doses of mitogen were used. Mononuclear cells from most patients (8 out of 10) also showed a decreased capacity to generate Con A-induced suppressor cell activity. These results support the hypothesis that in AIHA exists an immunoregulatory defect which might have a pathogenic role in the development of this disease.

In vivo and in vitro effects of 1,1-dimethylhydrazine on selected immune functions

The in vivo phase of the experiments reported here include the evaluation of immune function after short- or long-term treatment of mice with 1,1-dimethylhydrazine (UDMH). Long-term exposure (3 injections/week for 14 weeks) resulted in increased numbers of Jerne plaque-forming cells, a trend toward decreased induction of suppressor cell activity by concanavalin A (Con A), and no effects on mitogen-induced lymphocyte blast transformation (LBT), compared to saline-treated control mice. These effects were greatest at doses of 10 or 50 mg/kg, while higher doses had less of an effect. In vitro experiments were performed by adding UDMH to normal murine splenocytes in the LBT assay and con A-induced suppressor cell assay. The UDMH induced a significant enhanced response to lipopolysaccharide (LPS) at 10 and 50 μg/ml, and a suppressed response to both Con A and LPS at higher concentrations. The UDMH also caused a decrease in suppressor cell activity at 25 μg/ml. Selective abrogation of suppressor activity or alteration of the suppressor cell-helper ratio were suggested as possible mechanisms for the enhancement effect associated with UDMH.