Lyt-23+ cyclophosphamide-sensitive T cells regulate the activity of an interleukin 2 inhibitor in vivo

In vivo administration of interleukin 2 stimulates mitosis in thymus and bone marrow

We have used short-term, high-density cultures to demonstrate that interleukin 2 (IL 2) in picomolar amounts causes entry of approximately 2% of thymocytes from 3-month-old rats into mitosis. Newborn and fetal animals show a higher response reflecting a greater proportion of cells which have been shown to express IL 2 receptors at this age. In vivo administration of nanogrammes of IL 2 or injection of rats with syngeneic spleen cells which had been stimulated in vitro with concanavalin A to release IL 2 were also shown to increase the proliferation of both thymus and bone marrow cells. This suggests that IL 2, in amounts which could be produced by peripheral lymphoid tissue during immune responses, could act to increase the turnover of lymphocytes in bone marrow and thymus.

Decreased interleukin 2 inhibitor in sera of patients with autoimmune disorders

The lymphokine, interleukin 2 (IL-2), is an important modulator of cell-mediated immune (CMI) responses. We report here the detection of an inhibitor of IL-2 in normal sera by measuring the inhibition of thymidine incorporation in IL-2 dependent murine CTLL cells. The inhibitor, partially purified by Sephacryl S-200 gel filtration, eluted with the 60,000-70,000 mol. wt fraction. The factor was destroyed at 56 degrees C for 30 min and did not bind to Protein A Sepharose, suggesting that it is not an immunoglobulin G. Of 26 normal sera tested, 23 had significant levels of the inhibitor. Since connective tissue diseases are often associated with deficient CMI responses, we examined the levels of IL-2 inhibitor in 26 systemic lupus erythematosus (SLE) and 22 rheumatoid arthritis (RA) patients. Only 8 SLE and 12 RA patients had normal levels of the inhibitor. Of the 18 SLE patients with low or undetectable levels, 15 had clinically defined active disease and of the eight with normal levels, three had active disease. The decrease in the IL-2 inhibitor level did not correlate either with steroid or cyclophosphamide treatment or with serum levels of DNA binding and C3. These data suggest that the function of the inhibitor is to control IL-2 activity under normal conditions. Decreased levels of the IL-2 inhibitor in these patients might be explained either as a reduced requirement of this regulatory protein secondary to decreased IL-2 production or a defect of the cells responsible for the production of both IL-2 and its inhibitor.

Administration of slowly released recombinant interleukin 2. Augmentation of the efficacy of adoptive immunotherapy with lymphokine-activated killer (LAK) cells

When recombinant human interleukin 2 (r-IL-2) was given to mice by single subcutaneous (s.c.) injection it rapidly disappeared from the blood. However, administration of slowly released r-IL-2 using mini-osmotic pumps caused a significant prolongation of serum levels of IL-2. Using a method for assaying IL-2 in vivo, it was also demonstrated that both the viability and the cytotoxicity of lymphokine-activated killer (LAK) cells could be maintained at a high level in vivo by administration of slowly released r-IL-2 rather than by a single injection of r-IL-2. In addition, we successfully treated EL4-bearing mice by combination therapy consisting of LAK cells and slowly released r-IL-2.

Modulation of cellular immune responses in mice with disseminated histoplasmosis by recombinant interleukin-2

Depression of the cellular immune responses in mice with disseminated histoplasmosis is associated with deficient production of interleukin-2 (IL-2) by splenocytes. Therefore, we examined whether a highly purified preparation of IL-2, recombinant human IL-2 (rIL-2), could modify the cellular immune responses in infected mice and whether this lymphokine could alter the severity of histoplasmosis in animals. Exogenous rIL-2, at concentrations of up to 1,000 U/ml, failed to augment the proliferative responses to concanavalin A by unfractionated splenocytes or splenic T cells from mice infected for 1 week. In addition, rIL-2 did not modulate the plaque-forming cell response to sheep erythrocytes by splenocytes from these same mice. However, at week 3, rIL-2 in concentrations ranging from 10 to 1,000 U/ml considerably augmented the proliferative response to concanavalin A and plaque-forming cell response to sheep erythrocytes by splenocytes from infected mice. Kinetics studies demonstrated that rIL-2 exerted maximal immunoregulatory activity when added on day 0 or 1 to cultures of splenocytes. In vivo administration of rIL-2, 200 to 20,000 U/day, for 10 days to normal and 3-week-infected mice did not alter the proliferative activity of splenocytes to concanavalin A; 200,000 U of rIL-2 per day actually depressed the proliferative responses of splenocytes from normal and infected mice. In vivo, rIL-2 did not modify delayed-type hypersensitivity responses to sheep erythrocytes or to histoplasmin by normal and infected mice. Moreover, treatment with rIL-2 in vivo did not reduce the number of Histoplasma CFU in spleens of mice. Thus, despite the immunoenhancing effect of rIL-2 in vitro, this lymphokine failed to exert similar effects in vivo.

Mechanisms of immunosuppression associated with severe nonthermal traumatic injuries in man: production of interleukin 1 and 2

Depression of cell-mediated immunity in patients following severe traumatic injury has been well documented in vitro and in vivo. However, the exact mechanism of this defect is still controversial. In this study, we have investigated the ability of injured patients' peripheral blood mononuclear cells (PBMC) to produce two important immunoregulatory molecules, interleukin 1 (IL 1) and interleukin 2 (IL 2). Eighteen traumatic injury patients were studied during the course of their hospital stay and their results compared with a group of 18 normal age- and sex-matched controls. The results showed the following. (1) Production of IL 2 by normal PBMC in response to optimal doses of mitogen may vary with sex as well as age. (2) Adherent mononuclear cells from trauma patients produced at least as much IL 1 as normals. (3) IL 2 production, however, was markedly suppressed (normals, 1.6 +/- 0.2 U; traumatic injury, 0.6 +/- 0.1 U; P = 0.001) and persisted for as long as 50 days postinjury. OKT4+ cells were not significantly decreased at any time, nor were OKT8+ suppressor/cytotoxic cells increased at any time. Decreased IL 2 production in patients treated with steroids or those who were septic was not different from that in those patients who were not treated with steroids or were not septic. These results suggest that the cause of the defect in IL 2 production in traumatic injury patients is not related to a lack of the IL 1 signal, producer T cells, or Ia+ monocytes or to increased suppressor T cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Human interleukin 2. Quantitation by a sensitive radioimmunoassay

Using polyclonal and monoclonal antibodies to human recombinant IL-2 (rIL-2), we developed a sensitive radioimmunoassay (RIA) for quantitation of human IL-2. In this assay, microtitration plates pre-coated with an anti-rIL-2 monoclonal antibody (35H10), recognizing residues 59-72 of human IL-2, are incubated with serial dilutions of test samples. Captured IL-2 is quantitated by adding an affinity-purified rabbit anti-rIL-2 antibody followed by an 125I-labeled goat anti-rabbit IgG. Antibodies to chemically synthesized IL-2 peptides could replace the polyspecific rabbit anti-rIL-2 antibody as the second specific reagent in the assay. This configuration was more sensitive than others tested, approaching the level of detection of the conventional IL-2 bioassay, thus allowing detection of as little as 100-200 pg IL-2. Serum or plasma fluids, however, inhibited the assay, reducing its sensitivity by approximately 5-fold. This RIA correlated well with the conventional bioassay in measuring IL-2 levels in sera from IL-2-treated patients. This, and similar, RIAs may serve as a useful adjunct or alternative to the conventional IL-2 bioassay in detecting and quantitating human IL-2 in culture supernatants and clinical samples.

Advances in understanding cell interactions in tissue resorption. Relevance to the pathogenesis of periodontal diseases and a new hypothesis

Much of the connective tissue degradation that takes place in periodontal diseases is mediated by proteolytic enzymes. Previous studies have focused on the action of proteinases released by invading polymorphonuclear neutrophils and macrophages, and bacterial enzymes. In view of recent work establishing that resident connective tissue cells can be induced by cytokines to bring about the destruction of their own matrix, we propose a new hypothesis. In this we envisage that a critical step is the interaction of bacterial antigens with inflammatory cells, resulting in the production of a cytokine, interleukin-1. Our interpretation of in vitro evidence is that the loss of connective tissue attachment and bone matrix resorption in periodontal diseases is mediated by metalloproteinases such as collagenase and stromelysin released by cells of the periodontium. Such proteolytic destruction can be induced by interleukin-1, whose production may not be dependent on a specific microbial flora but may be triggered by a number of organisms. It is now clear that interleukin-1 has multiple actions on both immune and non-immune cells; these include the induction of lymphocyte differentiation and proliferation and the stimulation of bone and cartilage resorption, and prostaglandin and metalloproteinase synthesis by connective tissues. It seems likely that further knowledge about the production and function of this cytokine will have an increasing impact in many diseases that involve resorption, particularly since interleukin-1-like molecules can be produced by cell types other than monocytes/macrophages, including keratinocytes and fibroblasts.

Nonspecific inhibitor of DNA synthesis elaborated by T-acceptor cells. II. Requirements for its production and action

The production of a nonspecific inhibitor of DNA synthesis (nsINH) appears to be one of the final events in the T-suppressor cell circuit in mice exposed to contact sensitizers. We report here that: The nsINH suppresses the proliferative response to a polyclonal T-cell mitogen, concanavalin A (Con A), regardless of the dose of Con A used. It also suppresses DNA synthesis in lymphoid cells stimulated with alloantigens. This suppression can be completely eliminated by adding exogenous interleukin 2 (IL-2). DNA synthesis in lymphoid cells exposed to nsINH before the proliferative stimulus is uninfluenced so that activation of the lymphoid cells at the same time as exposure to nsINH seems to be a requirement for its action. Since the activity of nsINH can be absorbed by activated Lyt-1+ or Lyt-2+ lymphocytes, the early activated T cell appears to be a target of the action of nsINH. The production of nsINH is abolished or severely reduced by adult thymectomy. Natural killer (NK) cells are resistant to nsINH action and no interferon (IFN)-like activity can be demonstrated in nsINH preparation using a conventional assay for IFN.

Specific chemoimmunotherapy in tumor-bearing mice with extracted antigen, cyclophosphamide, and intrasplenic administration of interleukin-2

The effect of daily intrasplenic (I-SP) injection of interleukin-2 (IL-2) in conjunction with specific chemoimmunotherapy with extracted tumor antigens and cyclophosphamide was assessed with the use of methylcholanthrene (MCA)-induced fibrosarcoma in C3H/HeJ mice. Injections of 80 U of human IL-2 were delivered transcutaneously into the spleen (I-SP), which had been relocated to the subcutis with its blood supply intact. Six daily I-SP injections into mice bearing MCA-F tumors activated immune spleen cells (SPC), as evidenced by specific neutralization of the MCA-F, but not the antigenically different MCA-D tumor, in local adoptive transfer assays. The immune cell phenotype was Thy 1.2+ Lyt 2+, based upon abrogation of tumor neutralization after depletion with monoclonal antibodies and complement. In a second series of experiments, primary hosts bearing established MCA-F tumors underwent therapy with 1 microgram 1-butanol extracted, isoelectrophoretically purified TSTA injected subcutaneously, a single intraperitoneal (IP) dose of 20 mg/kg cyclophosphamide (CY), and/or either IP or I-SP IL-2 injection. Triple chemoimmunotherapy with I-SP, but not IP, IL-2 retarded tumor outgrowth more effectively than single or double treatment protocols. Furthermore, in a third series of investigations, the triple therapy group showed both decreased numbers and incidence of spontaneous metastases from a subcutaneous implant of clone 9-4, a highly metastatic variant of MCA-F. Indeed, 35% of hosts that received triple therapy, but none of the animals treated with other regimens, were free of lung metastasis (P less than 0.02). Thus, tumor resistance engendered by chemoimmunotherapy with TSTA and CY is potentiated in vivo by I-SP administration of IL-2.

Inhibition of suppressor cell generation by mouse serum in culture

Normal C57BL/6 mouse spleen cells cultured for five days in the presence of fetal calf serum (FCS-induced suppressor generation culture) were shown, in mixing experiments, to suppress the primary humoral response of freshly explanted C57BL/6 spleen cells against sheep erythrocytes (SRBC). This suppressor cell generation was largely dependent on the FCS concentration in the suppressor generation culture. Ten or 5% FCS effectively supported the generation of suppressor cells, but 1% FCS only marginally supported it. When mouse serum (MS) from normal C57BL/6 mice was added to the suppressor generation culture, it inhibited the generation of the suppressor cells. Sera from allogeneic mice and athymic nude mice were also effective. The effect of MS was resistant to heat treatment (56 degrees C, 30 min). The inhibitory activity of MS was not dialyzable, and concentrated into the fraction which was not precipitated by 50% saturation of ammonium sulfate and which was eluted at a concentration of about 0.2 M NaCl from a DEAE-Sephadex A-50 column. The active fraction of MS also effectively inhibited the growth of Ehrlich tumor cells in culture. Further, MS also inhibited the generation of Con A-induced suppressor cells. The inhibition by MS of FCS-induced suppressor generation was eliminated by an interleukin 2-containing preparation.

Interleukin 2-activated killer cells: generation in collaboration with interferon gamma and its suppression in cancer patients

The generation of lymphokine activated killer (LAK) cells by recombinant IL2 (rIL2) in collaboration with interferon gamma (IFN gamma) was examined in peripheral blood mononuclear cells (PBMC) from patients with malignant tumors of the digestive organs and breast cancer. LAK cytotoxicity could be induced by rIL2 at 10 units/ml in 10 of 12 patients and 20 of 37 using fresh autologous tumor cells and PK-1, an established solid tumor cell line as a target, respectively. Among 34 patients, in which titers of IFN gamma produced were assayed, 12 showed no IFN gamma production. All of these 12 patients had no or extremely low LAK activity, suggesting the correlation of LAK generation with the production of IFN gamma in response to rIL2. LAK induction by rIL2 in PBMC of cancer patients was almost completely inhibited by addition of anti-IFN gamma serum. Depressed LAK generation, which was accompanied by no or low levels of IFN gamma production, was partially restored by addition of exogenous recombinant IFN gamma. These results indicate that LAK induction by rIL2 in cancer patients involves the production of IFN gamma and its interaction with rIL2. The results also suggested the presence of a factor(s) suppressing LAK induction by rIL2 in the serum of cancer patients. Based on these results, the cancer patients could be divided into the following three groups. Group 1, in which the serum suppressor activity was undetectable, had the same level of LAK cytotoxicity in PBMC as healthy controls. Group 2 showed the serum suppressor factor and had the lower level of cytotoxicity in PBMC when cultivated in autologous serum (AS) compared to healthy controls. The depressed LAK induction in AS medium was restored to a normal level in culture with fetal calf serum (FCS) plus rIL2, or by addition of rIFN gamma, or high concentrations of rIL2 in AS medium. The last group (group 3), in which the serum suppressor factor was also found, had the lowest level of cytotoxicity compared to healthy controls. The LAK induction in these patients could not be restored to a normal level by culture in FCS medium, addition of exogenous rIFN gamma or high concentrations of rIL2, suggesting the possibility that the deficit of LAK generation in this group might involve the dysfunction or the lack of IL2 responder cells, in addition to the presence of a serum suppressor factor(s).

In vivo activity of interleukin-2: conversion of a stimulus causing unresponsiveness to a stimulus causing contact hypersensitivity by the injection of interleukin-2

The intravenous injection of hapten-modified (picrylated) cells causes unresponsiveness. When conventional or recombinant interleukin-2 (IL-2) is also injected, strong contact sensitivity occurs. This IL-2 is effective when given 7 hr after the injection of the picrylated cells or 2 days later, but has no effect when given beforehand. It is suggested that picrylated cells given intravenously fail to induce contact sensitivity secondary to a failure of IL-2 production, and that IL-2 may be one of the second signals which converts a 'tolerogenic' stimulus into an immunogenic stimulus.

Is IL-2 regulated by a serum inhibitor?

Normal murine serum inhibits the proliferation of cloned cytotoxic T lymphocytes driven by pure interleukin 2 (IL-2), indicating that a component of normal murine serum is directly inhibitory to IL-2-dependent proliferation. However, the effect is not specific to such cells, since an IL-2-independent variant cell, and a number of lymphoid tumor cell lines are similarly inhibited. Addition of purified IL-2 does not overcome the inhibition, although its degree is reduced. Fractionation of murine serum showed that there are at least two inhibitory activities, which migrate with globular proteins of molecular weights greater than or equal to 10(6) and 4 X 10(4), respectively, on gel chromatography. Neither of the activities was specific for IL-2-dependent cells. Furthermore, murine IL-2 is stable in murine serum in vitro, although it disappears rapidly from the circulation after intravenous injection. It is therefore unlikely that serum inhibitor of IL-2 is an important immunoregulator in vivo.

Consequences of cyclophosphamide treatment in murine lymphocytic choriomeningitis: evidence for cytotoxic T cell replication in vivo

Administration of a large dose (400 mg/kg) of cyclophosphamide (Cy) prior to infection with lymphocytic choriomeningitis virus (LCMV) suppresses the virus-immune cytotoxic T lymphocyte (CTL) response. Treatment with 150 mg/kg of Cy before, at the time of, or on the day after LCMV infection has little effect on CTL function. In contrast, when given on 2-7 days after LCMV, this dose profoundly depresses the day-8 CTL response and delays the onset of neurological disease. Administration of as little as 50 mg/kg of Cy has a marked effect on CTL activity when given 5 days after virus. Therefore it seems likely that CTL are replicating for 5 or 6 days during this primary response. Multiplication of these T cells is apparently completed by day 8, since inoculation of 150 mg/kg of Cy at this time has little effect on the level of CTL activity measured on day 9. The CTL activity is not reconstituted by in vitro culture with added helper factors. The interpretation that CTL are replicating in vivo following inoculation of LCMV is in accord with other analyses of virus-specific precursor frequency in primed and naïve mice.

Serum IL-2 inhibitor in mice. II. Molecular characteristics

The molecular characteristics of a serum IL-2 inhibitor were determined by fractionating active sera from normal and malaria-infected mice, and assaying inhibitory activity in blocking production and expression of IL-2 activity. Using isoelectric focusing and ion exchange chromatography, the activity resolved in a single peak (pI = 6.2). HPLC gel filtration resolved two peaks of activity (50,000 and 25,000 MW) which are probably related. The molecule is precipitated by 50% saturated ammonium sulphate, and is destroyed by heating above 56 degrees or by acidification below pH 4.

Serum IL-2 inhibitor in mice. I. Increase during infection

Serum from normal mice contains an inhibitor of interleukin-2 (IL-2) which probably interacts directly with IL-2. Athymic mice and normal mice kept under specific pathogen-free conditions do not show this activity, whereas mice infected with malaria parasites have increased serum levels of inhibitor. This IL-2 inhibitor may play an important part in regulating T-cell function.

Staining and fluorescence-activated cell sorter analysis of human lymphocytes using antibodies to a short, chemically synthesized human IL-2 peptide

A rabbit antibody against a chemically synthesized peptide (p84), encompassing residues 59-72 of mature human interleukin 2 (IL-2), has been shown to react specifically with natural or recombinant IL-2. This antibody was used in immunoperoxidase and immunofluorescence techniques for identification of IL-2-containing cells in human peripheral blood or tonsils. Lymphocytes were stimulated with T-cell mitogens (PHA, PWM), fixed, and incubated with affinity-purified anti-p84 antibody, followed by appropriately conjugated secondary antibodies. FACS analysis demonstrated a low fluorescence intensity in 5 to 15% of unstimulated cells. In contrast, 40-60% of mitogen-stimulated cells were stained at a high fluorescence intensity. Staining was inhibited by preincubating the anti-p84 antibody with the homologous peptide or recombinant IL-2, but not by unrelated peptides. In immunoperoxidase staining, anti-p84 antibody reacted selectively with an enriched T-cell population which was 95% Leu 5+, 80% Leu 3+, and 60% Tac+. Thus, this antibody to a synthetic IL-2 peptide reacts selectively with activated T cells, and may serve, therefore, as a useful tool for visualization and enumeration of IL-2-containing cells in blood and tissues.

Effector mechanisms of syngeneic anti-tumour responses in mice. II. Cytotoxic T lymphocytes mediate neutralization and rejection of radiation-induced leukaemia RL male 1 in the nude mouse system

We demonstrated the efficacy of a long-term cultured cytotoxic T-lymphocyte line, CTLL-D4, on tumour growth inhibition using athymic nude mice as recipients. CTLL-D4, specific for a unique surface determinant on a radiation-induced leukaemia RL male 1 of BALB/c origin, was obtained from the limiting dilution culture of MLTC cells performed between spleen cells of a CB6F1-nu/+ mouse immunized in vivo and RL male 1 stimulator cells, and cultured for several months in the absence of added TCGF as described in our preceding paper (Kuribayashi, 1985). The specific inhibition of tumour growth by CTLL-D4 was demonstrated both in Winn-type neutralization assay and in systemic transfer experiments. A subcutaneous inoculation of the mixture of CTLL-D4 and RL male 1 cells resulted in the complete inhibition of tumour growth, even at the effector to tumour cell ratio of 1:1, whereas non-cytolytic D4f, which was self-Ia antigen(s)-reactive, composed entirely of Lyt-1+23- T cells and derived originally from CTLL-D4 but completely lost its cytotoxic activity during culture with the irradiated syngeneic feeder cells alone, had no inhibitory effect at all. In the adoptive transfer studies, the subcutaneously established tumours were rejected by the single i.v. transfer of 2 X 10(7) CTLL-D4 cells into CB6F1-nu/nu mice. However, D4f was ineffective again in this systemic transfer system. When the effect of CTLL-D4 cells on tumour rejection in vivo was compared to that of non-cultured spleen cells hyperimmunized with RL male 1 cells, the former exhibited more rapid rejection in nude mice after i.v. transfer than the latter did, suggesting that CTLL-D4 cells also attack the tumour cells much more effectively as effectors in vivo. Thus, it is conceivable that CTLs are mainly involved in tumour rejection in this adoptive transfer system using RL male 1 tumour cells and athymic nude mice.

Ongoing hapten-specific delayed-type hypersensitivity prevents generation of cytolytic T lymphocytes to the same hapten

Cytolytic T lymphocytes (CTL) specific for trinitrophenyl (TNP)-altered self antigens can be generated in vivo through the simultaneous injection of TNP-modified syngeneic spleen cells and H-2-compatible, minor histocompatibility locus (Mls)-disparate auxiliary spleen cells into the footpads of mice. The latter stimulates host helper cells to produce differentiative and proliferative signals required for the generation of CTL. Advent of this protocol allowed investigation of the initiation of two different cell-mediated immune responses, delayed-type hypersensitivity (DTH) and the generation of CTL, in the same experimental animal. Mice presensitized for CTL were able to develop DTH as well as normal controls. However, when mice were first sensitized for DTH, they were thereafter incapable of generating CTL. This effect was hapten specific, relatively long lasting, and preventable by treating mice with cyclophosphamide before sensitizing for DTH. Adoptive transfer of lymphoid cells from DTH-immune mice conferred DTH reactivity upon naive recipients but not a suppressed CTL response. Therefore, cells mediating DTH were not responsible for suppression of CTL. The mechanism for suppression has been discussed from the viewpoint of the suppressor-T-cell circuits that are known to be generated when animals are sensitized for DTH and which are susceptible to treatment with cyclophosphamide.

Behavior of helper T lymphocytes in cyclosporine-mediated long-term graft acceptance in the rat

(LEW X BN)F1 cardiac allografts are rejected acutely (7 days) in unmodified LEW rats, yet survive indefinitely following cyclosporine (CsA) treatment (15 mg/kg im for 7 days) or in T-cell-deprived (B) recipients. Using these models, the function of T helper cells (Th) in the maintenance phase of CsA-mediated long-term graft survival was examined. With monoclonal antibody immunoaffinity fractionation techniques, Th (W3/25+OX8-) were separated from spleens of CsA-treated hosts 3-4 weeks after grafting (CsA-Th), from specifically sensitized (s-Th), or from normal ungrafted (n-Th) rats. Adoptive transfer of 60 X 10(6) CsA-Th into B recipients produced rejection of donor-specific, but not third-party grafts in 21 +/- 7 days, comparable to s-Th (17 +/- 4 days), but faster than n-Th (4-5 weeks, P less than 0.025). CsA-Th recombined with T cytotoxic/suppressor phenotype (CsA-Tc/s, OX8+W3/25-) in numbers contained in 100 X 10(6) CsA-T cells were ineffectual, even when supplemented with exogenous interleukin 2-rich conditioned medium (IL-2CM); in contrast 100 X 10(6) s-T cells + IL-2CM inevitably caused acute rejection in B hosts (11 +/- 3 days). Increasing numbers of Th incrementally to 100 X 10(6) augmented the effectiveness of s-Th (rejection in 13 +/- 2 days), but did not improve potency of CsA-Th (20 +/- 2 days). Suppressor activity produced by small numbers of contaminating CsA-Tc/s (c. 0.4%, 4-5 X 10(5) cells in 100 X 10(6) CsA-Th) accounted for extended graft survival in B recipients, as this small number of CsA-Tc/s transferred into untreated syngeneic rats increased test graft survival to c. 16 days (P less than 0.001). IL-2 production by spleen cells, depressed during CsA treatment, returned to normal levels 2-3 weeks following drug withdrawal, whereas transfer of CsA-Th into B recipients induced a shift of IL-2 levels from dramatically depressed to normal, findings suggesting normal IL-2 production by CsA-Th. This report demonstrates that an unresponsive state in CsA-treated animals is achieved despite the presence of fully potent donor-specific Th. Active suppressor activity plays a critical role in the maintenance phase of graft survival in rats treated transiently with CsA.

The generation of culture activated killer cells (AK) is interleukin-2-dependent and requires self-Ia recognition

Cytotoxic cells which lack major histocompatibility restriction for lysis are generated when murine spleen cells are cultured in the presence of FCS with or without allogeneic stimulation. The studies reported show that, following 3 days of culture with FCS, murine spleen cell cultures contain at least two cytotoxic populations. The first (AK-YAC), expresses an NK cell phenotype and target specificity while the second (AK-WEHI) shares the characteristics of the NC cell. Generation of the AK-YAC effector cell requires the presence of a pre-AK cytotoxic cell (Qa-5+, Lyt-2-) and is dependent on the generation of interleukin-2 (IL-2) during the culture period, while the AK-WEHI effector is independent of IL-2 production. IL-2 production in the cultures is shown to require syngeneic Ia recognition by an Lyt-1+, L3T4+ T cell. These findings suggest a role for IL-2 in the in vivo regulation of NCMC and describe a mechanism for its production in the absence of antigenic stimulation.

Augmentation of cell-mediated responses in vitro by a monoclonal anti-helper factor antibody

Previous studies have shown that monoclonal antibody AF3.44.4 has specificity for a constant region determinant on mouse antigen-specific helper factors and that it also binds to cultured T cells with functional helper cell characteristics. The antibody synergizes with antigen to enhance in vitro antibody responses; here we demonstrate that it will also enhance cell-mediated responses in vitro such as in the generation of proliferating cells in mixed lymphocyte responses and in the generation of specific killer cells in cytotoxic T lymphocyte cultures. The mechanism of AF3.44.4-generated enhancement was investigated. Increased levels of the lymphokines IL-2 and BCDF were detected in supernatants of AF3.44.4-treated cultures but the antibody itself could not replace interleukin-2 (IL-2), and would not stimulate primed cells in the absence of antigen. This type of monoclonal antibody which augments immunological responses in an antigen-dependent fashion may provide a new class of immunostimulant and a new approach to augmenting the responses of weak immunogens.

Mouse serum as a medium supplement for murine immune responses in vitro

In vitro generation of secondary anti-viral H-2 restricted cytotoxic T cells (Tc cells) alloreactive Tc cells, alloantigen-induced T cell proliferation, bacterial lipopolysaccharide (LPS)-induced B cell proliferation and anti-dinitrophenyl IgM and IgG antibody responses were used to evaluate pools of mouse sera (MS) and other animal sera as medium supplements by comparison with 5-10% fetal calf serum (FCS). Some batches of normal MS were comparable with FCS while others inhibited Tc cell responses when used at 1%, particularly with limiting stimulator cell numbers. In contrast, 2 pools of nude mouse sera and several pools of MS from thioglycollate-injected mice (TMS) used at 1% were consistently comparable with FCS at 5-10% in terms of in vitro generation of effector Tc cells and antibody secreting B cells. TMS at 1% was satisfactory for Tc cell responses either fresh, after heat inactivation at 56 degrees C for 30 min, or after storage for 6 months at -70 degrees C. 0.5% or 2% heat-inactivated rat and rabbit sera (but not guinea pig sera) were also satisfactory for Tc cell generation. Total thymidine incorporation into proliferating B or T cells was 5-15-fold lower in cultures with 1% normal MS, nude MS or TMS than with 5% FCS, but stimulation indices with 1% nude MS and TMS were similar to those with 5% FCS, whereas 1% normal MS apparently completely inhibited stimulation. One percent syngeneic TMS is a convenient, reliable alternative to 5-10% FCS in culture medium, supporting all the murine responses listed above.

Graft-vs.-host reactions: mechanisms and contemporary theories

A graft-vs.-host (GvH) reaction can be initiated by injection of immunocompetent lymphocytes into a histoincompatible host that is unable to reject these cells. The reaction is characterized by splenomegaly, hepatomegaly, lymph node atrophy, body weight loss, dermatitis, and diarrhea, often leading to mortality. The onset and severity of the GvH reaction are determined by differences in histocompatibility antigens between the donor and the acceptor, and by the number and nature of the transplanted allogeneic cells. Many different in vivo and in vitro systems have been devised for experimental studies of the GvH reaction. In several of these models, however, different parameters are measured. Furthermore, the conclusions drawn from these investigations sometimes contradict each other. This paper reviews the experimental data, and discusses the mechanisms underlying the GvH reaction.

Characterization of cell lines enhancing IL-2 production by human phytohemagglutinin-stimulated lymphocytes

Certain cell lines were found to significantly enhance IL-2 production by phytohemagglutinin-stimulated T lymphocytes, and the mechanisms involved in mediating such an enhancement have been studied. All B-lymphoblastoid cell lines (B-CL) tested had an enhancing capability, even lines which were immature, surface immunoglobulin negative, or negative for EBV-associated antigens or Fc receptors. Furthermore, a B-CL lacking HLA-A, B, and C, antigens as well as a HLA-DR-deficient mutant line enhanced IL-2 production. Autologous B-CL as well as allogeneic lines were able to augment IL-2 production. Cell lines from patients with T-cell acute lymphoblastic leukemia did not stimulate, while more mature, DR-positive T-cell lines did. Although all HLA-DR positive cell lines, regardless of their derivation, provided enhancement, several lines of evidence, including blocking experiments with anti-DR antibodies, indicated that the reaction was not HLA-DR mediated. The enhancing determinant(s) appeared to be cell associated since CL supernatants were ineffective, and it may serve as an important additional signal to the preactivated IL-2-producer T-cell.

Inhibition of interleukin-2 production by adherent cell factors from lepromatous leprosy patients

Twenty-four hour supernatants (MoF) were obtained from monocyte rich 2 h adherent cells of 19 leprosy patients and four healthy contacts. MoF from borderline and lepromatous patients produced 52-61% inhibition of human interleukin-2 (IL-2) production by a PHA conditioned T cell line (Jurkat). Non-adherent cell supernatants and MoF from tuberculoid and healthy individuals had little effect on IL-2 production. The suppression effected by MoF was in the first 12 h of initiation of PHA stimulated Jurkat cell cultures. Suppressive MoF did not interfere with (1) IL-2 release, (2) IL-2 utilization by Con A-induced T cell blasts or (3) constitutive proliferation of Jurkat cells. Such MoF were released spontaneously from adherent cells of bacilliferous leprosy patients but required in vitro antigen triggering in long term treated lepromatous patients. It is possible that the unresponsiveness associated with lepromatous leprosy is related to the inhibition of IL-2 production by suppressive factors, thereby, preventing the further expansion of antigen reactive T cells.

Mitomycin C-treated or irradiated concanavalin A-activated T cells augment the activation of cytotoxic T cells in vivo

The activation of cytotoxic T lymphocytes (CTL) in vivo after immunization of normal or cyclophosphamide-treated mice with allogeneic cells was strongly augmented by the administration of mitomycin C-treated or irradiated concanavalin A-activated spleen cells (Con A-spl). This effect of the Con A-spl was abrogated by treatment with Anti-Thy 1 antibody plus complement, and was therefore presumably mediated by activated "helper" T cells. (The term "helper" cell is only operationally defined in this context and indicates that the augmenting irradiation resistant T cells are obviously not CTL precursor cells). These observations indicated (i) that even the cytotoxic response against allogeneic stimulator cells suffers in vivo from insufficient "helper" T cell activity, and (ii) that the injection of Con A-spl may serve as a simple procedure to apply this "helper" activity in vivo. This procedure was at least as effective as the repeated injection of interleukin 2 (IL-2)-containing cell supernatants with up to four 30-unit doses of IL-2 per mouse. IL-2-containing cell supernatants were found to mediate similar effects only if injected into the footpads but not intravenously. This was in line with the reported observation that IL-2 has an extremely short half-life in vivo. The injection of Con A-spl was also found to augment the proliferative response in the regional lymph nodes.

Adoptive immunotherapy of established pulmonary metastases with LAK cells and recombinant interleukin-2

The activation of human peripheral blood leukocytes or murine splenocytes with interleukin-2 (IL-2) generated cells that were lytic in vitro for a variety of fresh tumor cells. The adoptive transfer of such lymphokine-activated killer (LAK) cells to mice with established pulmonary sarcoma metastases was highly effective in reducing the number (and size) of these tumor nodules when combined with repeated injections of recombinant IL-2. These findings provide a rationale for clinical trials of the infusion of human LAK cells generated with recombinant IL-2 as well as Phase I trials of the infusion of recombinant IL-2 systemically into humans.

Characterization of two suppressor cells that together prevent in vivo development of cytolytic T cells to hapten-altered self

Two suppressor cell populations that interact to down-regulate in vivo development of the cytolytic T-cell (CTL) response to trinitrophenyl-modified syngeneic spleen cells (TNP-SC) have been further characterized. Suppressor cells induced by the iv injection of trinitrophenyl-modified syngeneic spleen cells possess Thy 1.2 antigen. Their precursors are insensitive to pretreatment of host animals with cyclophosphamide (CY). Suppressor cells that arise after dermal sensitization with trinitrochlorobenzene are also Thy 1.2 antigen positive but their precursors are sensitive to pretreatment with CY. These characteristics of the two suppressor T cells (Ts) are identical to those of the two Ts that are generated by similar methodologies and that together suppress contact sensitivity (CS) to picryl chloride. Neither the CS nor CTL response was suppressed when host animals possessed only one set of Ts. In contrast to suppression of CS at the efferent phase, development of CTL was suppressed only when the two Ts were present early during sensitization (afferent phase). Since the results point to several similarities between the two sets of Ts that are active in the down-regulation of the CS and CTL responses, it is suggested that the two dissimilar immune responses directed to the same hapten, namely CS and CTL, may be controlled by the same suppressor cells. Since it appears that the two sets of Ts interact to affect different phases of the CS and CTL responses, down-regulation of each must be accomplished through different mechanisms.

Evidence of cells bearing interleukin-2 receptor at sites of disease activity in sarcoid patients

The frequency of cells reactive with anti-Tac monoclonal antibody (MoAb), which recognizes the interleukin-2 (IL-2) receptor, has been evaluated in cell suspensions from peripheral blood and bronchoalveolar lavage (BAL), and in frozen sections from involved tissues in 18 patients with active sarcoidosis. Peripheral blood lymphocytes of sarcoid patients do not bear Tac determinant and reduced numbers of Tac+ cells are inducible following PHA stimulation. On the other hand, significant numbers of lymphocytes reactive with anti-TacMoAb are present in the cells obtained from the BAL and a number of Tac+ cells infiltrate the lung, lymph node and conjunctiva. The finding of Tac+ cells in the BAL fluid and in other organs in patients with sarcoidosis provides evidence that some T cells in these involved tissues have the characteristics of IL-2 responder cells and thus the potential to absorb IL-2, supporting the hypothesis that T lymphocytes replicate in situ at sites of disease activity.

In vivo regulation of the cytolytic T cell response to hapten-altered self: suppressor T cells induced in the regional lymph nodes by exposure to syngeneic spleen cells

During the course of examining the in vivo development of the cytotoxic T lymphocyte (CTL) response to hapten-modified self antigens in mice, we have observed that it can be abrogated through prior exposure of the host's regional lymph nodes (LN) to normal syngeneic spleen cells (NSC). Suppression appeared to be antigen nonspecific and was best seen when animals were injected in the footpads with NSC at least 72 h before sensitization for CTL. The ability to prevent the development of the CTL response was restricted primarily to syngeneic splenic T and B cells since syngeneic thymocytes stimulated only partial suppression and syngeneic LN cells, as well as hapten-coupled syngeneic spleen cells, did not at all. Suppression appeared to be a local phenomenon in that the NSC induced transferable suppressor T cells to appear in the popliteal LN draining the footpads but not in spleens. In addition, animals splenectomized prior to injections of NSC showed abrogated CTL responses equivalent to sham-splenectomized animals indicating that the spleen does not contribute to the mechanism of suppression. Finally, when only one footpad was injected with NSC, suppression was seen in the draining popliteal node and not in the contralateral node. Taken together, the evidence suggests that the source of the suppression and the suppressor T cells may be attributed to an in vivo syngeneic mixed lymphocyte reaction occurring between responder cells of the draining LN and injected stimulator spleen cells.

Local production of Ia-inducing activity in experimental immunogenic uveitis

The production of soluble lymphokine products of T lymphocytes was studied in the aqueous of rabbits with uveitis induced by intravitreal injection of 2.0 mg of ovalbumin. Aqueous from uveitic eyes demonstrated Ia-inducing activity at a dilution of 1:50 which diluted out at 1:250. The control aqueous and sera from normal or uveitic animals were negative. While production of interleukin 2(IL-2) in uveitic eyes could not be demonstrated in vitro, control rabbit concanavalin A-induced supernatants of nylon-wool-purified T cells contained both Ia-inducing and IL-2 activity. These data demonstrate antigen-driven production of a lymphokine activity in the aqueous of the uveitic eye. Local production of lymphokine may be a potent mechanism for amplification of the inflammatory process in uveitis.

Characterization of interleukin 2 (IL-2)-dependent cytotoxic T-cell clones. V. Transfer of resistance to allografts and tumor grafts requires exogenous IL-2

The adoptive transfer of resistance to tumor grafts with cloned interleukin 2 (IL-2)-dependent cytotoxic T-cell lines was examined. Two clones were used: clone CTLL-A2 which recognizes H-2Dd determinants and clone CTLL-R5 which recognizes a unique cell surface antigen of BALB/c leukemia RL male 1. Systemic transfer of resistance with these clones was accomplished only when exogenous (rat or human) IL-2 was administered at the same time. Intraperitoneal injection of CTLL-A2 cells accelerated rejection of sarcoma Meth A (H-2Dd), but not ascites sarcoma BP8 (H-2k) or leukemia EL4 (H-2b) inoculated subcutaneously into C57BL/6 mice. CTLL-R5 cells were examined in local (Winn tests) as well as systemic transfer experiments. When mixed with leukemia cells before subcutaneous injection, they suppressed the growth of leukemia RL male 1 without exogenous IL-2. When injected intraperitoneally, CTLL-R5 cells inhibited the growth of subcutaneous grafts of leukemia RL male 1 only when exogenous IL-2 was administered at the same time. CTLL-R5 did not inhibit the growth of other radiation-induced BALB/c leukemias.

Differential effects of positive and negative proliferative stimuli on murine cytolytic and helper T-cell clones

Studies were performed to determine whether substances could be identified which exhibited differential regulatory effects--either positive or negative--on the growth of murine alloreactive cytolytic (Tc) and helper (Th) cloned T-cell lines. The following lines of evidence suggested that Tc and Th proliferate in response to the same growth factor (GF). (1) When GF-containing fluids from cultures of phorbol myristic acetate (PMA)-activated EL4 thymoma were fractionated by a variety of biochemical techniques. Tc and Th eluted together. (2) Absorption of GF-containing supernatants with either cloned Tc or cloned Th depleted GF activity for each to a similar extent, and GF eluted from either Tc or Th to which it had adsorbed supported the proliferation of Tc and Th equally well. (3) Lectin-depleted supernatants from cultures of concanavalin A (Con A)-activated Th stimulated the proliferation of Th as well as Tc. (4) Recombinant human interleukin (IL-2) supported the growth of Tc and Th with equal efficiency. On the other hand, the following observations indicated that Tc and Th differed in their responses to inhibitors of GF-driven proliferation. (1) Con A at greater than or equal to 0.3 micrograms/ml inhibited the GF-driven proliferation of each of three Th lines but not either of two Tc lines. To the contrary, Con A enhanced GF-dependent proliferation of Tc. (2) Like Con A, allogeneic splenocytes selectively depressed GF-driven proliferation of Th but not Tc. (3) A substance generated during the acid elution of GF from cells, possibly a modified fetal calf serum component, greatly reduced the GF-driven proliferation of Tc but not Th. These results suggest that differential control of the proliferation of Tc and Th in cellular immune responses may be achieved via negative regulatory signals and raise the possibility that substances which can selectively depress the proliferation of specific T-cell subsets might be found which would be of therapeutic value.

The production of T-cell growth factor (TCGF) in vivo in sheep

Lymph and supernatants derived from efferent lymphocytes leaving the popliteal lymph nodes of sheep responding to human red cells or dinitrophenylated bovine serum albumin were examined for the presence of T-cell growth factor (TCGF). Efferent cells from normal sheep, but not from antigen-stimulated sheep, were found to release low levels of TCGF when incubated in medium for 12 hr in the absence of any exogenous stimulus. High levels of TCGF were found in normal lymph and also in immune lymph collected from sheep during the first 6 hr of immune responses. There were no detectable levels of TCGF in lymph collected later in the response. The lymphokine appeared to be a single molecular species of 10,000-20,000 molecular weight as assessed by exclusion chromatography. Efferent cells expressing receptors for TCGF were found in efferent lymph during the first 12 hr of the response. The results demonstrate for the first time that TCGF is produced in vivo and that asynchrony exists between TCGF production and expression of receptors for TCGF on efferent cells released by the stimulated node. Based on the known kinetics of previously reported synergistic factors, mitogenic factors, and T-cell-replacing factors in sheep efferent lymph and their physical characteristics it was concluded that the TCGF detected in lymph is distinct from these factors.

Establishment of experimental malignant glioma-specific cytotoxic T lymphocyte clone by T cell growth factor

In an attempt to facilitate the long-term proliferative growth and subsequent cloning of cytotoxic T lymphocytes (CTL's) against syngeneic murine 203-glioma (20-methylcholanthrene-induced ependymoblastoma of C57BL/6 mouse origin), sensitized T lymphocytes from tumor-bearing mice were cultured in the presence of T cell growth factor (TCGF). Of five clones established by a limiting dilution technique, two clones (G-CTLL 1 and 2) exhibited tumor-specific cytotoxicity. G-CTLL 1 cells, which possessed much higher cytotoxic activity than G-CTLL 2 cells, were further analyzed. G-CTLL 1 cells were maintained in a TCGF-dependent exponential proliferative culture for over 18 months and continued to mediate an extremely high cytotoxic activity with the target specificity (50- to 100-fold increases over the peak cytotoxic activity of sensitized T lymphocytes in tumor-bearing mice). Their phenotypes of surface antigens were Thy-1+ (weak positive), Lyt-1.-2.+3+, and asialo-GM1-, and their cytotoxicity was blocked by adding only anti-Lyt-2 monoclonal antibodies. These results indicated that the cloned cells originated from CTL's. The cloned cells were characterized by the production of immune interferon with the glioma antigen-stimulation, suggesting that the immune interferon could enhance the cytotoxic activity of the CTL clone at the site of a clone-target cell recognition event.

Inhibition of IL 2 responsiveness of mitogen-stimulated lymphocytes by SMLR-generated plastic adherent suppressor cells

The proliferative response of spleen cells to concanavalin A (Con A) can be abrogated by plastic adherent suppressors generated in syngeneic mixed lymphocyte cultures of spleen cells. The addition of exogenously produced interleukins does not overcome the suppression, indicating that the suppressors are not simply competing for available growth factors. To examine the effect of the suppressors on IL 2 production and responsiveness, spleen cells were stimulated with Con A in the presence of the suppressors and assayed both for ability to produce IL 2 and for ability to bind IL 2. The culture supernates of suppressed spleen cells contained normal titers of biologically active IL 2, indicating that the suppressors do not inhibit IL 2 production or inactivate IL 2 after it is produced. Since IL 1 is required for IL 2 production, the failure of the suppressors to affect IL 2 production suggests that the suppressors have no effect on either production of, or responsiveness to, IL 1. The suppressed cells did, however, display a substantial reduction in ability to absorb IL 2 activity from a standard IL 2 preparation. The reduced frequency of IL 2 reactive cells did not appear to be due to a cytotoxic reaction insofar as no difference in viable cell recovery was noted between suppressed and nonsuppressed cultures at the time of assay. The suppressors therefore appear to inhibit the expression of IL 2 responsiveness without inhibiting the production of IL 2.

Changes in the capacity of macrophages and T cells to produce interleukins during murine malaria infection

Interleukin 1 (I1-1) produced by activated macrophages and interleukin 2 (I1-2) released by a subset of T lymphocytes upon antigen or mitogen stimulation are the soluble mediators involved in the mechanism of T-cell activation, proliferation, and differentiation. Since these T-cell responses are depressed during malaria infection, the capacity of macrophages to produce I1-1 following lipopolysaccharide (LPS) stimulation and that of lymphocytes to release I1-2 upon stimulation with concanavalin A (Con-A) in mice infected with either nonlethal Plasmodium yoelii (NLPY) or lethal Plasmodium berghei (PB) malaria parasites was analyzed. The results show that while adherent cells from spleen or peritoneal exudates of infected mice were able to produce I1-1, although to a different extent in the two infections, splenic lymphocytes were unable to produce I1-2, but capable of responding to it. This suggests that the diminished T-cell responses in malaria might be due to a defect of I1-2 synthesis.

T helper cell lines that augment in vivo cytotoxic T-cell responses to minor alloantigens

We have investigated the ability of long-term cultured T helper (Th) cell lines to help an in vivo cytotoxic T lymphocyte (CTL) response to non-H-2 alloantigens (minor antigens). Th cell lines specific for various single or undefined minor antigens were selected by regular restimulation with antigen in vitro. They were antigen specific and H-2 restricted in proliferation assays and were found to be able to help primary CTL responses to multiple minor antigens and secondary CTL responses to single minor antigens. Although the Th were antigen specific they did not determine the specificity of the CTL. Th cells were both necessary and limiting for an effective CTL response indicating that "helper-independent" CTL are not in themselves sufficient to generate a strong in vivo response. Under conditions where a CTL response was clearly H-2 restricted, Th cells were not. Thus, the Th cells appeared to be activated by reprocessed antigen rather than antigen on the surface of the injected antigenic cells even though the CTL themselves reacted directly to the injected antigen.