Immune-interferon (IFN-gamma), macrophage-activating factors (MAFs), and colony-stimulating factors (CSFs) secreted by T cell clones in limiting dilution microcultures, long-term cultures, and by T cell hybridomas

LEF-1 negatively controls interleukin-4 expression through a proximal promoter regulatory element

Lymphoid enhancer-binding factor 1 (LEF-1) and T cell factor (TCF-1) are downstream effectors of the Wnt signaling pathway and are involved in the regulation of T cell development in the thymus. LEF-1 and TCF-1 are also expressed in mature peripheral primary T cells, but their expression is down-regulated following T cell activation. Although the decisive roles of LEF-1 and TCF-1 in the early stages of T cell development are well documented, the functions of these factors in mature peripheral T cells are largely unknown. Recently, LEF-1 was shown to suppress Th2 cytokines interleukin-4 (IL-4), -5, and -13 expression from the developing Th2 cells that overexpress LEF-1 through retrovirus gene transduction. In this study, we further investigated the expression and functions of LEF-1 and TCF-1 in peripheral CD4+ T cells and revealed that LEF-1 is dominantly expressed in Th1 but not in Th2 cells. We identified a high affinity LEF-1-binding site in the negative regulatory element of the IL-4 promoter. Knockdown LEF-1 expression by LEF-1-specific small interfering RNA resulted in an increase in the IL-4 mRNA expression. This study further confirms a negative regulatory role of LEF-1 in mature peripheral T cells. Furthermore, we found that IL-4 stimulation possesses a negative effect on the expressions of LEF-1 and TCF-1 in primary T cells, suggesting a positive feedback effect of IL-4 on IL4 gene expression.

Th2-Specific Protein/DNA Interactions at the Proximal Nuclear Factor-AT Site Contribute to the Functional Activity of the Human IL-4 Promoter

IL-4 is a pleiotropic immunoregulatory cytokine secreted by activated Th2, but not Th1, cells. The proximal IL-4 promoter contains MARE, C/EBP, P0, octamer-like, P1, and activating protein-1 elements. The half c-Maf binding site (MARE), P0, and P1 sites were previously shown to be involved in Th2-specific transcriptional activity. Except the MARE and P1 site, the molecular basis for Th2 specificity of the P0 site has not been analyzed. Here, we provide the first detailed analysis of the P0 binding factors and show that in Th2, but not in Th1, cells, NF-AT and proteins of the activating protein-1 family are involved in cooperative binding to the P0 and the adjacent octamer-like site. In the mouse Th2 D10 cells, Oct-1/Oct-2 are also found to participate in formation of the P0-binding complexes. Mutation, deletion, and methylation interference analysis demonstrate that both the P0 and the octamer-like sequence are required for inducible binding. Furthermore, we provide the first report of the functional relevance of each site in the human IL-4 promoter by mutagenesis/transfection analysis and demonstrate that the octamer-like, P0 and P1 sites are important for the biologic function of the IL-4 promoter. The MARE site, although it was shown to be critical for the function of the murine IL-4 promoter, does not appear essential for human IL-4 promoter activity in Jurkat T cells. These findings suggest that besides c-Maf, another Th2-specific factor(s) may be involved in tissue-specific expression of the IL-4 gene.

Characterization of constitutive and inducible transcription factors binding to the P2 NF-AT site in the human interleukin-4 promoter

Interleukin-4 (IL-4) is a pleiotropic immunomodulatory cytokine secreted by T helper 2 cells. The IL-4 promoter contains multiple sites with DNA sequences homologous to the IL-2 NF-AT binding site. One of these sites--the P2 site--located between -173 and -150 was previously found to be flanked by two octamer-like motifs. NF-ATp/c and octamer proteins were suggested to bind to this region and to cooperatively activate the promoter activity (Chuvpilo et al., 1993). To precisely analyze the P2-binding factors we used antibodies against NF-ATp, NF-ATc, Fos, Jun, Oct-1 and Oct-2 in EMSA. We show here that nuclear extracts from T-cells form two P2-binding complexes--a PMA/ionomycin-inducible and a constitutive one. The PMA/ionomycin-inducible complex contains NF-ATp/c, Fos and Jun. No octamer binding factors could be detected in either of the two complexes. Analysis of the precise DNA contact points of the two complexes showed that both complexes are formed in the center of the NF-AT consensus site. No DNA contact points could be detected in the octamer-like motif site. Furthermore, purified recombinant POU domains of Oct-1 and Oct-2 failed to bind to the P2 site, suggesting that this site is not an independent octamer-binding site. Therefore, the DNA sequence at -173 to -150 of the IL-4 promoter is a binding site for NF-ATp/c and AP-1. Octamer proteins are unlikely to cooperate with NF-ATp/c at this site.

Bcl-2 down-regulates the activity of transcription factor NF-kappaB induced upon apoptosis

Among the many target genes of the transcription factor NF-kappaB are p53 and c-myc, both of which are involved in apoptosis. This prompted us to investigate the role of NF-kappaB in this process. We report that NF-kappaB is potently activated upon serum starvation, a condition leading to apoptosis in 293 cells. Similar to Bcl-2, a transdominant-negative mutant of the NF-kappaB p65 subunit partially inhibited apoptosis, indicating a direct involvement of the transcription factor in induction of cell death. As expected, the p65 mutant suppresses kappaB-dependent gene expression. Surprisingly, transiently or stably overexpressed Bcl-2 had the same effect. The transcription inhibitory activity of the two proteins correlated with their cell death protective potential. Like Bcl-2, the related protein Bcl-xL but not Bcl-xS was able to suppress kB-dependent transcription. Bcl-2 inhibited NF-kappaB activity by an unusual mechanism. It did not prevent the release of IkappaB in the cytoplasm but down-modulated the transactivating potential of nuclear p65. These data show that NF-kappaB can participate in apoptosis. We suggest that at least part of the anti-apoptotic potential of Bcl-2 may be explained from a hitherto undiscovered activity of Bcl-2 in controlling nuclear gene expression.

Cloning and sequencing of a cDNA fragment from Plasmodium chabaudi chabaudi that contains repetitive sequences coding for a potentially lysine-rich aspartic acid-rich protein

Screening of a cDNA library (prepared in lambda gt11) of the blood stages of Plasmodium chabaudi chabaudi (AS) with immune serum has revealed an antigen the elicits a strong antibody response in infected mice. The clone (clone 6) expressing that antigen contains a 0.7 kb insert and produces a beta-galactosidase fusion protein of about 150 kDa. In Western blot analysis performed on parasite extracts, monoclonal antibodies and polyclonal sera prepared against the fusion protein revealed that the fusion protein contains part of a malarial protein of 93 kDa. Northern hybridization with clone 6 insert as probe detected a plasmodial RNA of about 3.2 kb, which could well code for a protein of this size. The insert hybridized to a single EcoRI fragment and a single HindIII fragment in genomic Southern blotting, suggesting that the gene is present in one copy in the P. chabaudi genome. The DNA sequence of clone 6 insert predicts a hydrophilic, acidic polypeptide consisting of seven repeats of 23-34 amino acids rich in lysine (24%) and aspartic acid (17.5%).

Differential effects of glutathione depletion on T cell subsets

Glutathione (GSH) is known to play an important role in various lymphocyte functions. We now report that different T cell subsets express different requirements for intracellular GSH. Depletion of intracellular GSH by buthionine sulfoximine (BSO), a specific inhibitor of GSH biosynthesis, decreases the proportion of CD8+ cells (i.e., increases the CD4+/CD8+ ratio), and inhibits particularly the generation of large blast-like CD8+ cells and cytotoxic T lymphocyte (CTL) activity. CTL activity is restored by administration of exogenous GSH. Differential effects of GSH depletion were also seen at the level of individual T cell clones. The CD4+ helper T cell clone D10.G4.1.HD was found to express a high rate of interleukin 2 (IL-2) dependent DNA synthesis even after severe depletion of intracellular GSH, whereas other T cell clones including the clone 29 were severely inhibited by BSO. The results of these studies suggest that the decreased intracellular GSH levels of HIV-1 seropositive persons are probably not (directly) responsible for the selective depletion of the CD4+ T cell subset but may be responsible for a cellular dysfunction of the CD8+ subset and for the ultimate failure of the CTL to control the viral infection in these patients.

CD4 rat x rat and mouse x rat T cell hybridomas produced by fusion of established T cell lines and clones to W/Fu (C58NT)D

Previously, fusion of established T cell lines or clones has been claimed to be difficult. We now report our experiences in the fusion of both long term cultures of rat T cell clones and mouse T cell lines to rat W/Fu (C58NT)D. Upon fusion of rat T cell clones the hybrids obtained expressed antigen specificities identical to those of the parent clones. In addition, C58 was used for interspecies hybridisation of murine T cell lines. The specificity of intra- and inter-species hybrids was maintained by subcloning. We conclude that the C58 cell line can be used to generate continuously growing monoclonal T-cell reagents of sufficient stability using both intra- and inter-species hybridisation.

Interleukin-2 mRNA expression, lymphokine production and DNA synthesis in glutathione-depleted T cells

The stimulation of DNA synthesis in lymphocyte populations was previously shown to depend strongly on the intracellular glutathione (GSH) level. Since T cell growth is known to depend on interleukin 2 (IL-2), the experiments in this report were designed to determine whether intracellular GSH depletion may inhibit IL-2 production or the IL-2 dependent DNA synthesis. Our experiments revealed that IL-2 production and DNA synthesis of mitogenically stimulated splenic T cells have indeed different requirements for GSH. The addition of relatively high concentrations of GSH (5 mM) to cultures of concanavalin A (Con A)-stimulated splenic T cells was found to augment strongly the DNA synthesis but inhibited the production of IL-2. Moderate intracellular GSH levels, however, are apparently not inhibitory for IL-2 production, since intracellular GSH depletion by cysteine starvation or by graded concentrations of DL-buthionine sulfoximine (BSO) had virtually no effect on IL-2-specific mRNA expression and the production of T cell growth factor (TCGF). The DNA synthesis activity, in contrast, was strongly suppressed after GSH depletion with either method. As in cultures of splenic T cells, GSH depletion had no substantial effect on the induction of IL-2 mRNA and TCGF production in several mitogenically stimulated T cell clones. Taken together, our experiments suggest that complex immune response may operate best at intermediate GSH levels that are not too high to inhibit IL-2 production but sufficient to support DNA synthesis.

Macrophages regulate intracellular glutathione levels of lymphocytes. Evidence for an immunoregulatory role of cysteine

Macrophages consume cystine and generate approximately equivalent amounts of acid-soluble thiol. Stimulation of macrophages with bacterial lipopolysaccharide (LPS) or tumor necrosis factor (TNF) strongly augments the amount of thiol released into the culture supernatant. Cysteine constitutes most of the acid-soluble thiol. The intracellular glutathione level and the DNA synthesis activity in mitogenically stimulated lymphocytes are strongly increased by either exogenously added cysteine, or (syngeneic) macrophages. This cysteine dependency is observed even in the presence of relatively high extracellular cystine concentration as they occur in the blood plasma. The extracellular cysteine concentration also has a strong influence on the intracellular glutathione concentration, viability, and DNA synthesis of cycling T cell clones. Moreover, the cysteine concentration in the culture medium on Day 3 and Day 4 of a 5-day allogeneic mixed lymphocyte culture (i.e., in the late phase of incubation) has a strong influence on the generation of cytotoxic T cell activity, indicating that regulatory effects of cysteine are not restricted to the early phase of the blastogenic response. The inhibitory effect of cysteine starvation on the DNA synthesis of the T cell clones and on the activation of cytotoxic T lymphocytes can be explained essentially by the depletion of intracellular glutathione, since similar effects are observed after treatment with buthionine sulfoximine (BSO), a specific inhibitor of the glutathione biosynthesis. BSO has practically no influence, however, on the N alpha-benzyloxycarbonyl Ne-t-butyloxycarbonyl-L-lysine-thiobenzyl-ester (BLT)-esterase activity and hemolytic activity of the cell lysates from cytotoxic T cells against sheep red blood cells (perforin activity). Taken together, our experiments indicate that cysteine has a regulatory role in the immune system analogous to the hormone-like lymphokines and cytokines. It is released by macrophages at a variable and regulated rate and regulates immunologically relevant functions of lymphocytes in the vicinity.

Cytotoxic effector cells of the immune system

The organism contains several types of cytotoxic cells which are able to lyse host and foreign cells. Cytotoxic T-lymphocytes (CTL) appear to play the most important role among the killer cells but other lymphatic cells, such as natural killer (NK) cells and lymphokine-activated killer (LAK) cells as well as macrophages are also highly effective in the lysis of appropriate targets. The various cytotoxic effector cells differ distinctly concerning origin, phenotype, morphology and target cell specificity, but they bear the common feature that they destroy the target cells in a contact-dependent non-phagocytotic process. CTL are characterized by typical lysosomal granules and by the expression of a characteristic pattern of surface molecules. They recognize specific antigens which are presented in context with molecules of class I major histocompatibility complex (MHC). NK cells, on the other hand, kill the appropriate targets without prior immunisation and without requiring recognition of MHC molecules at the target cells. They also bear a typical pattern of surface markers which differ in several aspects from that of CTL. Human NK cells are further characterized by peculiar cytoplasmic granules with parallel tubular arrays which are not present in other cytotoxic cells. LAK cells constitute an additional, only recently described, killer cell population which arise from lymphatic cells in the presence of interleukin-2. They appear to represent a functional unique cytotoxic effector cell system with an exceptionally wide target cell spectrum including normal and malignant cells of different origin. LAK cells, however, show a profound heterogeneity concerning the expression of phenotype surface markers and it is not yet clear whether they are a unique cell line. By electron microscopy they display peculiar intranuclear inclusion bodies which may be associated with prolonged stimulation by interleukin-2. CTL, NK and LAK cells appear to possess similar mechanisms for cytolysis including secretion of pore-forming proteins, serine proteases and other proteins. Furthermore, they are able to trigger the cleavage of DNA in the target cell nucleus by a hitherto unknown pathway. Macrophages differ substantially from other cytotoxic effector cells concerning morphology, phenotype, kinetic of activation and target cell spectrum. They perform a variety of functions whereby contact-dependent target cell lysis represents only one of their properties. After target cell binding they release over 20 different molecules such as interleukin-1 and tumor necrosis-factor-alpha as mediators for cytolysis.(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of guinea pig leukocyte antigens using interspecies T cell hybrids

In the guinea pig system, there are no T lymphocyte tumors available. In addition, in this species the production of T cell lines in vitro for analysis of T cell markers or function proved to be difficult. As an alternative approach, guinea pig X mouse and guinea pig X rat T cell hybridomas were obtained by fusion of guinea pig T cells with HAT-sensitive mouse or rat thymomas. In ten fusions a total of 578 hybrids were produced and kept in culture for periods ranging from weeks up to several months. The highest yield was obtained when the Mb C 12 line was used as tumor parent. BW 5147 and the rat thymoma W/Fu(C58NT)D gave slightly lower fusion efficiencies. The yield depended also on the pretreatment of the parental cells. Activation by MLR proved to be most effective. A number of interspecies hybrids expressed guinea pig T cell differentiation antigens as detected by a cell ELISA. The positive hybrids were recloned several times and exhibited a stable expression of these markers, even after continuous culture for more than 2 months. Western blot analysis was used to confirm antigen expression at the protein level by comparing the hybrids with both parental cells. The hybrids expressed the proteins of the guinea pig lineage. No reaction was observed with the murine or rat thymomas. Therefore, the application of interspecies T cell hybrids provides an alternative for studies of guinea pig T cells. The cells are easy to grow and to clone and may be stored frozen in liquid nitrogen. The hybrids should permit analysis at the clonal level also for functional studies.

Treatment with gamma-interferon triggers the onset of collagen arthritis in mice

We investigated the effect of gamma-interferon (gamma-IFN) on the development of type II collagen (CII)-induced arthritis. DBA/1 mice were immunized with rat CII and 16 days later, were treated with subcutaneous injections of recombinant rat gamma-IFN into the right paws twice a week. Compared with controls, the gamma-IFN-treated mice developed arthritis with a higher frequency and severity. Immunohistochemical analysis of gamma-IFN-treated paws from CII-immunized mice revealed an increase in the numbers of class II antigen-expressing cells and an infiltration of CD4+ lymphocyte-like cells. The auto-antibody response toward CII was suppressed by gamma-IFN treatment. The findings implicate gamma-IFN in a role that triggers arthritis by enhancing local inflammatory processes in the joints, or possibly, by permitting homing of T cells to the joints.

Interleukin 1 as a tumor cytostatic mediator released from tumor ascites-treated macrophages

Peritoneal macrophages from DBA/2 mice, elicited by injection of Corynebacterium parvum (C.p.), were in vitro activated to Eb tumor cytostasis by incubation with tumor-induced ascites that was harvested 7 days after intraperitoneal Eb injection. The active cytostasis-mediating compound was found to be interleukin 1 (IL 1). When tumor ascites was fractionated according to molecular weight size, the most active IL 1-inducing fraction was found to comprise molecules of greater than 100,000 daltons. The data show that tumor-bearing hosts are capable of producing compounds that induce a high IL 1 secretion which may enable macrophages to mount an antiproliferative effect against tumor cells.

Preactivation of macrophages in mice acutely infected with Schistosoma mansoni

This paper shows that peritoneal murine macrophages become preactivated in vivo during the course of a Schistosoma mansoni infection. Thus, less macrophage-activating factor (MAF) was required to induce in vitro tumoricidal and schistosomulicidal activity in macrophages from S. mansoni-infected mice than in macrophages from uninfected control animals. Moreover, the respiratory burst activity, as measured by chemiluminescence, was enhanced in macrophages from S. mansoni-infected mice as compared to controls, whether or not lymphokine (LK) was present in the macrophage cultures. This response appeared at 3 weeks and persisted at least until 12 weeks after infection. Interferon-gamma (IFN-gamma) is most likely involved in the mechanisms leading to such an increased cytolytic and oxidative activity, since in vitro experiments showed: 1) that less IFN-gamma was required to induce tumoricidal activity in macrophages from infected as compared to macrophages from uninfected animals, 2) that the activity of (2'-5')-adenylate synthetase (2'-5' A-synthetase), an enzyme strongly induced by IFN, was elevated in cells from livers of S. mansoni-infected mice.

Immunogenetic analysis of cellular interactions governing the recruitment of T lymphocytes and monocytes in lymphocytic choriomeningitis virus-induced immunopathology

The Lyt2+ class I major histocompatibility complex (MHC)-restricted virus-immune T cells that induce murine lymphocytic choriomeningitis (LCM) are targeted onto radiation-resistant cells in the central nervous system of virus-infected mice. The use of appropriate bone marrow radiation chimeras as LCM virus-infected, (immunosuppressed recipients for immune T-cell transfer has established that, though bone marrow-derived cells can stimulate virus-specific cytotoxic T lymphocytes (CTL) in spleen, they do not reconstitute the barrier to T-cell recruitment from blood to cerebrospinal fluid. This is true for chimeras made up to 8 months previously, even though the inflammatory monocytes and macrophages in such chimeras are all of donor bone marrow origin. Radiation-resistant cells in the spleens of these chimeras are also still able to further stimulate virus-immune CTL. There is no requirement for H-2 compatibility between virus-immune T lymphocytes and secondarily recruited monocytes, or T cells of an inappropriate specificity. The key event in LCM immunopathology may thus be localization of T cells to the antigen-presenting endothelium in brain, leading to the secretion of mediators that promote the nonspecific recruitment of monocytes and other T cells.

Biological effects of a rat monoclonal anti-mouse IFN-gamma antibody produced by in vitro immunization

This paper describes the biological effect of monoclonal antibodies to murine IFN-gamma produced by in vitro immunization with only several nanograms of rIFN-gamma. Four mAbs binding to rIFN-gamma were selected. mAb U7 was characterized in detail and shown to bind specifically to rIFN-gamma in a Western blot and to specifically inhibit the antiviral effect of rIFN-gamma and natural IFN-gamma. The activities of IFN-alpha, beta and IL2 were not affected. The M phi activating effect of both rIFN-gamma and natural IFN-gamma was also inhibited by mAb U7. Thus, we showed that it is possible to produce specific mAbs with very small amounts of cytokines by in vitro immunization.

The cellular immune response to a purified antigen from Leishmania mexicana subsp. amazonensis enhances the size of the leishmanial lesion on susceptible mice

Immunization of BALB/c mice with gp10/20, a glycoconjugate purified from Leishmania mexicana subsp. amazonensis, induced a delayed-type hypersensitivity response to the antigen, and a significant increase was elicited in the size of the lesion induced by a subcutaneous infection with this parasite. The increase in the lesion size was observed when mice were immunized by the subcutaneous and the intraperitoneal routes. The subcutaneous immunization with gp10/20 was unable to reverse the prophylactic effect of an intravenous injection of irradiated promastigotes. An L3T4+ T-cell line specific for gp10/20 was able to transfer this lesion-enhancing effect and specific delayed-type hypersensitivity reactivity to normal syngeneic recipients. The same T-cell line was a good producer of a hematopoietic growth factor, granulocyte-macrophage colony-stimulating factor.

Efforts to produce human cytotoxic T-cell hybridomas by electrofusion and PEG fusion

Cytotoxic human T cells from different sources were fused with different types of human T-lymphoma cells and mouse B-myeloma cells using variations of the polyethylene glycol (PEG) method and electrofusion. Both techniques yielded proliferating hybridomas. The frequency of wells with proliferating hybridomas depended on the tumor fusion partner used; the best results were obtained with HSB-1, whereas fusions with JURKAT-1 and HPB-1 did not yield any hybridomas. For one tumor cell line (HSB-1), considerably more hybridomas were obtained with electrofusion than with the PEG fusion (with or without heat shock). There was no consistent relationship between the presence or absence of cytotoxic activity of the T lymphocytes against the tumor fusion partner and the yield of hybridomas. In human-human as well as in human-mouse hybridomas most of the lymphocyte derived chromosomes were lost. Four of the more than 600 hybridomas tested showed transient cytotoxic activity, but in none of them this function could be immortalized. Two of the hybridomas obtained with CEM-1 as tumor fusion partner expressed low levels of lymphocyte-derived CD3 antigens. Two hybridomas obtained with HSB-1 were highly invasive in vitro in rat hepatocyte cultures, whereas HSB-1 tumor cells were not.

Radiation leukemia virus-transformed immunocompetent T cells. II. Antigen-induced macrophage migration inhibition factor and leukocyte migration inhibition factor production

OVA-specific T cells were immortalized by infection with radiation leukemia virus (RadLV). Some clones derived from such population were shown to exhibit helper activity. We then tested clones without such function and found among them some that secreted macrophage migration inhibition factor (MIF) and leukocyte migration inhibition factor (LIF) upon exposure to the antigen in vitro. The lymphokine-producing clones, which were Thy-1+, Ly-1+ and Ly-2-, did not secrete MIF and LIF constitutively. Like other antigen-specific T cells, the immortalized clones could not be stimulated by free soluble antigen but required macrophages for presentation and for triggering the lymphokine production. The antigen-activated clones exclusively produced MIF and LIF, but not interleukin 2 or colony-stimulating factor. They neither provided helper activity nor induced delayed-type hypersensitivity. The data suggest that the T-cell clones carry the antigen receptors and that their antigen-inducible biological function is restricted to the migration inhibitory factor production.

B cell-stimulatory factor 1 (BSF-1) promotes growth of helper T cell lines

T cell-derived supernatants (SN) that contain B cell-stimulatory factor 1 (BSF-1) and lack IL-2 promote the growth of the IL-2-dependent T cell line, HT-2, as well as three other clones or lines of T cells that can provide help to B cells. The BSF-1 purified from these SNs promotes growth of HT-2 cells approximately 50% as effectively as purified IL-2. A potential involvement for contaminating IL-2 in the BSF-1 preparations was excluded by the demonstration that anti-BSF-1 mAbs blocked the BSF-1-induced growth of HT-2 cells; in contrast, these antibodies did not block the IL-2-induced proliferation of the HT-2 cells. In addition, anti-IL-2 mAbs or anti-IL-2-R antibodies blocked the HT-2 growth-promoting activity of purified IL-2, but not BSF-1. Finally, BSF-1 promoted only a very modest growth of Con A-induced T cell blasts, and failed to induce significant growth in seven other cytotoxic, alloreactive, and long-term T cell lines. Taken together, these results indicate that in addition to its known effects on resting and LPS-stimulated B cells, BSF-1 can promote growth of certain subsets of activated T cells, in particular, those that provide help to B cells.

In vivo activation of macrophages by T cell-derived lymphokines: killing of tumor cells and schistosomula of Schistosoma mansoni

We investigated the role of T cell-derived lymphokines for macrophage activation in vivo. We show for the first time that macrophages from casein-pretreated mice can be primed in vivo by intraperitoneal injection of immune interferon (IFN-gamma) and can be triggered by lipopolysaccharide (LPS) in vitro to kill schistosomula of S. mansoni. Similar results were obtained for the activation of tumoricidal macrophages. Injection of casein-pretreated mice with concanavalin A (Con A)-induced supernatant of a long-term T cell clone containing IFN-gamma and macrophage cytotoxicity inducing factor 2 (MCIF2), however, induced macrophage activation in vivo without further addition of LPS in vitro. These experiments show that macrophages can be activated by lymphokines in vivo. In addition, the data suggest that a combination of IFN-gamma with MCIF2 might be more effective than IFN-gamma alone. These data may be relevant for the strategy of treating cancer and infectious diseases with lymphokines.

Suppression of cytotoxic T-lymphocyte activation by pyruvate and L-alanine

The activation of cytotoxic T lymphocytes (CTL) in allogeneic mixed-lymphocyte cultures was found to be strongly inhibited if 1-3 X 10(-2) M L-alanine or the structurally and biochemically related substance pyruvate was present in the period from 7 to 19 or from 19 to 120 hr. The cytotoxic response was not inhibited when L-alanine or pyruvate was present during the first 7 hr of the culture period. L-Alanine produced also little or no suppression, if added on Day 3 of the culture. L-Lactate or D-alanine at similar concentrations was not suppressive during the entire culture period. The suppression by pyruvate and L-alanine was strongly reduced by 1 X 10(-4) M adenosine. Adenosine in combination with an interleukin-2 (IL-2)-containing EL-4-cell supernatant was even more effective. Pyruvate and alanine (1-3 X 10(-2) M) also inhibited the DNA synthesis in mixed-lymphocyte cultures on Day 5 by about 50%, but both substances had practically no effect on DNA synthesis in cultures that had been supplemented with an IL-2-containing EL-4 supernatant. They had also no effect on the IL-2-dependent proliferation of several T-cell clones or of concanavalin A-activated thymocytes. These relatively selective regulatory effects of pyruvate and L-alanine may be useful for the analysis of the biochemical pathways during lymphocyte activation and/or for a selective manipulation of the immune response.

Influence of delayed immune reactions on human epidermal keratinocytes

The epidermal changes that occur in human cutaneous immune responses have been investigated in the tuberculin reaction and in the lesions of tuberculoid and lepromatous leprosy and cutaneous leishmaniasis. In each situation, there was a dermal accumulation of monocytes and T cells, and the epidermis exhibited thickening. In the tuberculin response, the thickness of the epidermis sometimes doubled in 48-72 hr, and this was attributed to increases in both size and number of keratinocytes. In addition, the phenotype of the keratinocytes changed from Ia- to Ia+. Similar changes in keratinocyte Ia-antigen expression occurred in the epidermis overlying untreated tuberculoid leprosy and cutaneous leishmaniasis lesions, but not in lepromatous leprosy. We suggest that one or more epidermal growth factors may be generated in the course of a delayed immune reaction in the dermis.

Killing of schistosomula of Schistosoma mansoni by macrophages: induction by T-cell clone-derived lymphokines and interferon-gamma

The induction of schistosomulicidal activity of peritoneal macrophages by concanavalin A-stimulated supernatants from long-term T-cell clones and by interferon-gamma (IFN-gamma) was investigated in detail. Optimal conditions of in vitro macrophage activation by T-cell clone supernatants were established. Macrophages from 13-week S. mansoni-infected mice responded to lymphokine activation as well as resident macrophages from uninfected mice. IFN-gamma was shown to play an essential role in induction of schistosomulicidal macrophage activity: recombinant IFN-gamma at high concentration could induce schistosomula killing, and an anti-IFN-gamma antiserum inhibited the induction of schistosomulicidal activity by T-cell clone supernatants. Our data also indicate that macrophage activation could be obtained by IFN-gamma in synergy with other lymphokines in the supernatant of long-term T-cell clones. Macrophages from mice injected with T-cell clone supernatants were primed in vivo and triggered to kill schistosomula in vitro in the presence of lipopolysaccharide (LPS). The data demonstrate that lymphokines produced by T-cell clones and, in particular, IFN-gamma can participate in the activation of schistosomulicidal macrophages.

Activation of macrophage tumor cytotoxicity by the synergism of two T cell-derived lymphokines: immune interferon (IFN-gamma) and macrophage cytotoxicity-inducing factor 2 (MCIF2)

This report describes the role of T cell-derived lymphokines in induction of macrophage (M phi) tumor cytotoxicity. M phi tumor cytotoxicity was tested with the murine M phi-like tumor PU5-1.8. This M phi-like tumor reacts to stimulation with T cell-derived lymphokines and shows tumor cytotoxicity comparable to resident peritoneal M phi. The experiments demonstrate that immune interferon (IFN-gamma) secreted by T cell clones in limiting dilution microcultures was insufficient to induce M phi tumor cytotoxicity. Induction of M phi tumor cytotoxicity by T cell-derived supernatants with quantities of IFN-gamma undetectable in the IFN assay, however, was completely inhibited by an antiserum raised against recombinant IFN-gamma. Taken together, these results could be thus explained: (a) a T cell-derived lymphokine distinct from but serologically cross-reactive with IFN-gamma induces M phi tumor cytotoxicity, and (b) IFN-gamma activity in supernatants positive for induction of M phi tumor cytotoxicity escapes detection in the IFN assay but can still be inhibited by the anti-IFN-gamma antiserum in the M phi tumor cytotoxicity assay. The latter explanation requires positive evidence for another T cell-derived lymphokine inducing M phi tumor cytotoxicity together with IFN-gamma. This lymphokine was found in the supernatant of T cells in limiting dilution cultures and a long-term T cell clone and was called M phi cytotoxicity-inducing factor 2 (MCIF2). MCIF2 synergizes with IFN-gamma in induction of M phi tumor cytotoxicity; IFN-gamma and MCIF2 alone were ineffective.

Activation of macrophages by lymphokines from T-cell clones: evidence for different macrophage-activating factors

The data reported in this paper demonstrate that macrophage-activating factors (MAFs) are a heterogeneous group of T-cell-derived lymphokines. Two long-term T-cell clones, Cl 96 and PK 7.1.2E8, were potent sources of MAFs (MAF96 and MAF7.1.2E8). These MAFs could be distinguished by differential activation of macrophages. Activation of resident murine macrophages with MAF7.1.2E8 enhanced RNA and glycoprotein synthesis, hexosemonophosphate shunt (HMPS) activity, release of oxygen metabolites (O-2 and H2O2), pinocytosis and tumor cytostasis, whereas no effect on schistosomula killing and tumor cytolysis could be observed. In contrast, MAF96 enhanced glycoprotein synthesis, HMPS activity, release of oxygen metabolites and prostaglandin E, schistosomula killing, and tumor cytostasis and cytolysis, while RNA synthesis and pinocytosis were decreased. These findings show that MAFs from both T-cell clones share some properties but markedly differ in others. In addition, the macrophage-activating properties of MAF96 but not of MAF7.1.2E8 could selectively be inhibited by a rabbit anti-lymphokine antiserum. This demonstrates a serological difference between MAF activities from both clones. Although at optimal concns both MAFs were active in the absence of lipopolysaccharide (LPS), the activity of suboptimal doses of MAF96 but not of MAF7.1.2E8 could be enhanced by LPS. These findings show that different MAFs from T-cell clones may be useful to clarify molecular mechanisms of macrophage activation.