Human hybridoma suppressor factor acts selectively on CD4+ cells.

A human thymus cell hybridoma secretes an immunosuppressive lymphokine, referred to as hybridoma suppressor factor (HSF). This factor suppresses polyclonal immunoglobulin (Ig) production as well as Interleukin-2 (IL-2) production in pokeweed mitogen (PWM)-stimulated peripheral blood mononuclear cells (PBMC). Similar suppression of Ig and IL-2 production was observed in reconstituted cultures of CD4+ cells and non-T cells. Here we analysed, further, the mechanism of HSF-mediated suppression of Ig and IL-2 production. We demonstrated that HSF inhibited PWM-induced IL-2 production by CD4+ cells but not by CD8+ cells and its suppressive activity on Ig production was totally abrogated by preabsorption with CD4+ cells, but not by CD8+ cells. These results indicate a subset specific action of HSF.

Abnormal lymphocyte function in scleroderma: a study on identical twins.

This paper describes immunologic studies on a set of identical twins discordant for the presence of scleroderma. The affected twin had a low absolute T-cell count, low numbers of T4 helper/inducer cells, and an increase in the T8 suppressor/cytotoxic cell count. The T cells of the patient responded poorly to mitogens and to allogeneic and autologous stimuli. By contrast, T-cell-helper activity for pokeweed mitogen-induced IgM synthesis was markedly enhanced in the patient. Furthermore, activated mononuclear cell supernatants from the patient markedly enhanced the synthesis of collagen by normal cultured fibroblasts. The unaffected twin by contrast displayed normal responses in these assays. The results suggest that the immunologic defects in scleroderma are not entirely genetically determined.

Impaired autologous mixed lymphocyte reaction with normal concanavalin A-induced suppression in adult polymyositis/dermatomyositis.

Polymyositis/dermatomyositis (PM/DM) is an autoimmune disorder of unknown aetiology. In order to study whether immunoregulatory abnormalities might be involved in this autoimmune state, we investigated the autologous mixed lymphocyte reaction (AMLR) and concanavalin A-induced suppressor cell function (Con A-induced suppression) in adult patients with primary PM/DM. We found the AMLR to be significantly depressed in patients; responsiveness could not be enhanced by increasing the numbers of non-T stimulator cells in culture, nor by varying the day on which cultures were harvested. Con A-induced suppression of T cell proliferative responses to mitogenic stimuli was normal. These findings implicate abnormal immunoregulation in the pathophysiology of PM/DM. Further, the dissociation of AMLR reactivity from Con A-inducible suppression suggests that events important for immunoregulatory competence may occur in the AMLR culture, despite the absence of an observed proliferative response.

Mechanisms of Listeria monocytogenes-mediated modulation of tumor growth.

Studies using Listeria monocytogenes as an antitumor agent were initiated to determine the requirements for Listeria-mediated tumor inhibition to occur. When Strain 13 guinea pigs were injected with an admixture of viable Listeria and a methylcholanthrene-induced fibrosarcoma in a ratio of 1 bacterium to 100 tumor cells, Listeria had a marked capacity to inhibit tumor growth. This confirms an earlier study in our laboratory (M. M. Dustoor, A. Fulton, W. Croft, and A. A. Blazkovec, Infect. Immun. 23:54-60, 1979). At no time did animals exhibit overt symptoms of disease as a result of Listeria infection. Animals treated with antilymphocyte serum, which had previously been shown to abrogate T-cell functions, were no longer able to suppress Listeria-tumor cell mixtures. Treatment in vivo with carrageenan, a macrophage-inhibitory agent, also abrogated Listeria-mediated tumor inhibition. These results suggest that Listeria-mediated inhibition requires intact T-lymphocyte and macrophage function. Experiments in which Listeria was given in admixture with the tumor cells or in the opposite flank demonstrated that the antitumor effects require intimate association of the Listeria and tumor cells. Histopathological studies, showing that macrophages and lymphocytes are the predominant inflammatory cells present at sites of tumor destruction, further suggest a role for these cells in Listeria-mediated inhibition. Animals which had rejected prior Listeria-tumor cell inocula were resistant to rechallenge with the homologous tumor for more than 1 year. This work thus confirms in vitro studies demonstrating that both lymphocytes and macrophages are required for Listeria-mediated tumor inhibition to occur. This study demonstrates that viable Listeria can have potent antitumor effects without causing overt disease as a result of Listeria infection.

Antitumor activity of Listeria monocytogenes on a guinea pig fibrosarcoma.

Listeria monocytogenes-mediated tumor inhibition was studied in strain 13 guinea pigs by using a methylcholanthrene-induced fibrosarcoma (MCA-1). Mixtures of Listeria and tumor cells in ratios of 1:100, 1:200, or 1:400 (Listeria:MCA-1 cells) led to significant suppression of tumor growth. Intralesional injection of tumors on day 6 posttransplantation led to the regression of a highly significant number of tumors. Animals receiving injections of Listeria, either in a mixture with tumor cells or intralesionally, displayed enhanced skin test reactivity to a tumor extract. Tumor regressors were resistant for at least 2 to 3 months after the initial transplant to rechallenge with MCA-1 cells. Thus, with this particular tumor-host system, Listeria was successfully employed as an antitumor agent with no visibly detrimental side effects to the host.

Acquired cellular resistance, delayed hypersensitivity, and altered macrophage migration in Listeria monocytogenes-infected guinea pigs.

A Listeria monocytogenes infection in guinea pigs was used to study the interrelationship between antigen-induced macrophage migration inhibition, delayed-type hypersensitivity, and acquired cellular resistance. Early after infection (at 2 and 7 days), very significant enhancement of macrophage migration was observed. Migration inhibition was detected beginning on day 14 and was uniformly observed only on day 21 of the infection, after which a shift again to enhancement was seen. The early detection (by day 2) of migration enhancement suggested that this assay may be more sensitive than assessment of delayed type hypersensitivity in vivo, which in this system was first detectable only on day 4. Acquired cellular resistance, as measured by enhanced survival following a high dose challenge with Listeria, was present from day 7 after infection until at least day 60. By splenic clearance studies, however, acquired cellular resistance was present only until day 14 after infection, suggesting that in this system splenic clearance was not a very reliable criterion for measuring acquired cellular resistance.

Blastogenesis as an in vitro correlate of delayed hypersensitivity in guinea pigs infected with Listeria monocytogenes.

Randomly bred guinea pigs of both sexes were injected intracardially with one-half a 50% lethal dose of Listeria monocytogenes. When these animals were skin tested with 30 mug of a water-soluble extract of sonically disrupted Listeria, animals had uniformly detectable levels of delayed-type hypersensitivity (DTH) 6 days after infection. Histological examination of skin test reaction sites, after fixation in Helly fixative and Giemsa staining, revealed a classical tuberculin-type infiltrate consisting primarily of mononuclear cells with few polymorphonuclear cells. Many of the small vessels showed perivascular cuffing. When purified peritoneal exudate lymphocytes from these animals were cultured in vitro in the presence of various concentrations of Listeria antigen, it was fount that the optimal antigenic dose for specific antigen-induced incorporation of [3H]thymidine varied for individual animals. In contrast to the early onset of uniformly detectable levels of in vivo DTH, in vitro lymphocyte blastogenesis was not uniformly demonstrable until 14 days postinfection and remained highly significant on days 21, 28, and 84 postinfection. At 7 days postinfection, lymphocytes from 7 of 17 animals were capable of undergoing sifnificant blastogenesis. The Listeria antigen preparation was not mitogenic for peritoneal exudate lymphocytes from normal animals. It was found that no direct correlation exists between the in vivo levels of DTH and in vitro blastogenesis. Cell donors showing significant in vitro blastogenesis nevertheless were also skin test positive for most animals tested. Humoral antibody was found to play no significant role in the immune response of guinea pigs to a primary infection with Listeria monocytogenes.