Human immunosuppressive factors produced by T cell hybridoma

A Human OKT8-positive T cell hybridoma was established by using concanavalin A (ConA)-activated peripheral blood mononuclear cells (PBMC) fused with CEM-AGR cells. A culture supernatant of the established T cell hybridoma HI4.2D6 inhibited the mitogen induced proliferation of peripheral blood mononuclear cells (PBMC). It inhibited IL-1-, IL-2, or IL-3-dependent proliferation of each factor-dependent mouse cell lines. While the inhibitory activity of IL-1-induced proliferation was stable, that of IL-2- and IL-3-induced proliferation was abrogated within a week at 4 degrees C. Inhibition of IL-2-dependent growth was also observed using human IL-2-dependent cells, but the growth of other factor-independent human hematopoietic cell lines was not affected at all. By gel filtration, the activity inhibiting IL-2- or IL-3-dependent proliferation was found in the fractions with approximate molecular weight of 18,000 and 100,000.

Modulation of the immunosuppressive activities by blastocoelic fluid during rabbit pregnancy

Temporal variation in immunosuppressive activity was determined in biological samples such as embryo-foetal fluids (blastocoelic- or amino-allantoic fluid) and blood collected from pregnant and pseudopregnant rabbits. Each of the fluids to be analyzed was pre-incubated with mitogen stimulated human lymphocytes for 48 h and then inhibition of [3H]thymidine incorporation or IL-2 receptor expression was estimated. Both means of assessing immunosuppression indicated variations in the suppressive activity throughout pregnancy. This was observed in embryo-foetal fluids but not in autologous peripheral blood nor in homologous pseudopregnant blood. At days 9-13 of pregnancy, the immunosuppressive effects of blastocoelic fluids were higher than that of the autologous sera, reached a peak at days 12 and 13 and declined thereafter, to reach the lowest levels. In order to further characterize the biological activity of day-12 blastocoelic fluid and autologous serum, they were submitted to ultracentrifugation. No suppressive activity could be demonstrated in the lipoprotein fractions. But all the activity was found in the protein fraction. Precipitation with cold ethanol confirmed that the biologically active compound was a protein. Furthermore, results obtained after ultrafiltration suggest biologically active compounds of high mol. wt (greater than 300 kDa). From the above findings, we can suggest that in the rabbit, there is no pregnancy specific systemic immunosuppression. We can also infer that (1) the immuno-tolerance of the mother towards the embryo is more due to a localized effect; (2) this effect decreases with the progression of gestation and (3) a high mol. wt factor is responsible for the immunosuppression.

Purification of a suppressor lymphokine (SL) from a human T-cell line

Human T leukemia cell line 81-66-45 spontaneously releases into the medium a suppressor lymphokine (SL), able to inhibit PHA-stimulated normal peripheral blood T cell proliferation. Ion exchange and gel filtration chromatography were used successfully to isolate and purify this immunosuppressive lymphokine from culture supernatants. When the purified suppressor lymphokine was characterized with SDS-polyacrylamide gel electrophoresis under reducing conditions, it was found to be a single protein chain of 66,000 daltons. Titration curves of the purified suppressor lymphokine indicated that the inhibitory activity is dose dependent. The suppressor lymphokine is cytostatic and its addition to the peripheral blood lymphocytes (PBL) did not change the cell number or cell viability. This factor was stable at pH 2.0-8.5 and at 56 degrees C for 30 minutes. The structural relationship of this lymphokine with other T cell factors is discussed.

Characterization and analysis of soluble suppressor factor from early human decidual cells

To assess the role of decidual cells (DC) in the maintenance of pregnancy, immunosuppressive activity of culture supernatants from human DC were investigated. Dispersed DC suspensions from decidual tissue of early pregnancies were prepared by an enzyme digestion method using collagenase and DNase, and were enriched over 90 per cent without contamination of macrophages and lymphocytes in the fraction, with specific gravity between 1.033 and 1.044 (fraction 2 [Fr2] ) by a Percoll discontinuous density gradient method. The culture supernatants of Fr2 cells suppressed the responses of normal peripheral blood lymphocytes to PHA, MLR, and killer T cell generation at the 50 per cent concentration. To determine the mechanism of the immunosuppressive activity of the culture supernatants, the effect of the supernatants on interleukin-2 and gamma-interferon production, as well as IL-2 receptor expression, on PBL was investigated. The supernatants from 3 x 10(6)/ml of DC cells inhibited not only IL-2 and gamma-INF production, but also IL-2 receptor expression, compared with normal controls. The supernatants also suppressed immunoglobulin (IgG and IgM) production by pokeweed mitogen-stimulated B cells. To purify the suppressor factor from culture supernatants of DC, serum free culture supernatants of 3 x 10(6)/ml of DC, which showed 32 per cent of inhibitory activity on MLR, were applied to gel filtration. Fractions between mw 67,000 and 43,000 suppressed the MLR. These results suggest that DC from decidua of early pregnancy excrete an immunosuppressive factor with a molecular weight between 43,000 and 67,000 daltons.

Human suppressor factors constitutively produced by T-T cell hybridomas: functional and biochemical characterization

We have recently developed a new method (Hybridoma 6:589, 1987) for the generation of human T-T cell hybrids. This method is based on a new selection procedure that involves cloning the hybrids in soft agar, screening by HLA-typing or appropriate functional tests and recloning by limiting dilution. T-T cell hybrids were separated from the parent line on the basis of their ability to form colonies in soft agar, whereas the parent lymphoblastoid T cell lines did not. HAT medium was not used in our selection procedure. Using this method, we have succeeded in developing human T-T cell hybrids (as determined by HLA-typing) constitutively producing B cell growth factor (BCGF) (Hybridoma 6:589, 1987) or suppressor factors. These hybrids were obtained by fusing MLC or Con A T cell blasts with cells from the Molt 4 or Jurkat lymphoblastoid T cell lines. T-T cell hybridomas, derived by fusing Con A-stimulated lymphocytes with cells from the Jurkat T cell line, produced suppressor factors inhibiting: (1) proliferative response in vitro of human peripheral blood mononuclear leukocytes to mitogens and to allogeneic cells in mixed lymphocyte culture; and (2) immunoglobulin synthesis and secretion by mononuclear leukocytes in the PWM-induced differentiation system in vitro. A suppressor factor with these inhibitory properties was also identified in supernatants of the Jurkat T cell line. These suppressor factors were ammonium sulphate precipitable, pH 2 labile, non-dialyzable and they were inactivated by treatment at 56 degrees C for 30 minutes. They exhibited a molecular weight in the range of 50,000-70,000, as determined by gel filtration, and were not gamma or alpha interferon or lymphotoxin/TNF. They did not lyse human lymphoblastoid tumor cell lines nor did they affect the viability and cell numbers of human mononuclear cells even after prolonged incubation (88 hr). They appeared to be cytostatic rather than cytotoxic molecules. The Jurkat suppressor factor is different from those produced by the hybrids on the basis of: (a) different isoelectric points; and (b) the ability of the Jurkat factor to arrest proliferation to PHA of human mononuclear cells in the S phase, whereas the 160 and 169 factors arrest proliferation at the G1 phase of the cell cycle. Certain of these suppressor factors (produced by the hybrids 153, 160, 170, and the Jurkat T cell line) also inhibited proliferative responses of mouse lymphocytes in vitro. In contrast, suppressor factors produced by the 169 and 77 hybrids did not inhibit any murine responses.

Suppression of lymphocyte proliferation in vitro by macromolecules in the vesicle fluid and tissue extracts of hydatidiform mole

This study examines the effects of vesicle fluid and tissue extracts from hydatidiform mole trophoblast on lymphocyte proliferation in vitro. Samples were obtained by direct aspiration of vesicles (hydatidiform mole vesicle fluid (HMF] or homogenization of molar tissues (hydatidiform mole extract (HME] following therapeutic uterine evacuation of hydatidiform mole. Dialyzed and lyophylized HMF pooled from two patients exhibited a 30% suppression (P less than 0.05) of mitogen-induced lymphocyte proliferation at a concentration of 12.5 micrograms protein/ml. Similarly, lymphocyte transformation was significantly suppressed (P less than 0.05) by HME at concentrations of 500 and 250 micrograms/ml. Molecular weight chromatography of HME resolved 4 protein fractions. Fraction 3 (35--50 kDa) and fraction 4 (less than 35 kDa) significantly suppressed mitogen-induced lymphocyte transformation while fractions 1 and 2 demonstrated no immunosuppression. Heat treatment (56 degrees C, 30 min) abolished the immunosuppressive activity of HME as well as fractions 3 and 4. These results suggest that hydatidiform mole trophoblast contains heat-labile macromolecules which suppress mitogen-mediated lymphocyte transformation. Such trophoblast-derived factors may interfere with maternal rejection of the allograft.

Human embryo associated immunosuppressor factor(s) from pre- and post-implantation stages share some similarities

The present study demonstrates that embryo associated immunosuppressive factor(s) (EASF) secreted by the human embryo at pre- and post-implantation stages share some similarities. Human EASF was partially purified from embryo growth media of in vitro fertilized ova and from first trimester pregnancy sera. Non-pregnancy sera were fractionated in parallel. During each step of purification the fractions were tested for immunosuppressive properties using concanavalin A-stimulated lymphocyte proliferation assay. Analysis of EASF positive fractions on SDS-PAGE identified 14 kDa and 24 kDa molecules in embryo growth media and pregnancy sera. No such molecules were found in control sera, suggesting that these factors are embryo associated. The relationship of pre- and post-implantation EASF was also analyzed by EASF binding assay using murine anti-EASF antibody, which was raised against EASF isolated from embryo growth media. Results show that murine antibody bound to EASF purified from pregnancy sera, but not to identical fractions from control sera, indicating that these post-implantation EASF possess some similarity with pre-implantation EASF. Results also indicate that a species of suppressor factors present in embryo growth media and pregnancy sera were unique for their origin. Presence of these three EASFs at various stages of gestation may play a role in suppressing maternal cellular immune responses thereby preventing maternal rejection of the embryo.

Lung derived surface active material (SAM) inhibits natural killer cell tumor cytotoxicity

Natural killer cells have been identified in lung tissue but have been found to have significantly less tumor cytotoxicity than natural killer cells found elsewhere in the body. The natural killer cells in the lung are still functional, since their killing can be enhanced by Interleukin-2. The surface active material (SAM) of lung lining fluid has been shown to have immunomodulating activity, including the suppression of lymphocyte blast transformation and enhancement of macrophage tumor cytotoxicity. We studied the effect of SAM purified from lung lining fluid on natural killer cell tumor cytotoxicity. SAM markedly inhibited tumor killing (Percent cytotoxicity of cells alone: 41 +/- 7.3% (mean +/- SEM); cells plus SAM: 10 +/- 9.7%, p less than 0.02). Further studies demonstrated that some phospholipids, including phosphatidylcholine, the major phospholipid of SAM, also significantly inhibited natural killer cell tumor killing. This inhibition of natural killer cell tumor cytotoxicity could be reversed by the addition of Interleukin-2 to the natural killer cells. These studies demonstrated that the surfactant found in lung lining fluid significantly inhibited natural killer cell tumor cytotoxicity and this effect could be reversed by Interleukin-2.

Purification and analysis of an antigen-specific suppressor factor from a T cell hybridoma specific for phenyltrimethylamino hapten

The synthetic monovalent antigen L-tyrosine-p-azophenyltri-methylammonium (tyr (TMA)) induces in A/J mice, a cascade of regulatory T cells in the absence of any detectable effector function (e.g., CTL, delayed-type hypersensitivity, etc.). An important component of the activated T cells is a first order suppressor T cell or Ts1 that is Ly-1+2-, functions only at the afferent limb of the anti-TMA response, binds the TMA ligand and bears cross-reactive idiotypes associated with anti-TMA antibodies. This Ts1 produces a suppressor factor (TsF1) that binds the TMA ligand, bears the cross-reactive idiotypes and I-J determinants and functions to induce an idiotype-specific Ts2 population. To study the biochemistry of this TsF, use was made of T cell hybridomas that constitutively produce TMA-TsF1 (8A.1 and 8A.3). The TsF1 was purified from culture supernatant or cell extracts by (NH4)2SO4 precipitation, reverse phase HPLC and either affinity chromatography or by preparative IEF. The TsF1 has an isoelectric point of 6.5 and a m.w. of 26,000 or 62,000 as analyzed by SDS-PAGE or high performance molecular sieve chromatography. Its precipitation in 30 to 40% (NH4)2SO4; elution pattern from reverse phase high performance columns; its capacity to bind to a mAb specific for L-glutamic acid 60L-alanine30-L-tyrosine10 (GAT)-TsF1 strongly suggest that this protein belongs to the same family of proteins as do the GAT-TsF1 described previously. Most noteworthy is that although these TsF1 proteins show remarkable similarities, they are absolutely specific in their biologic activity; TMA-TsF1 will not suppress the response to GAT-BA-TNP and GAT-TsF1 will not suppress the response to TMA-BA-TNP. Thus the TMA-TsF1 represents a second example of a unique group of Ag-specific proteins whose function is to induce or activate other suppressor T cells in the primary immune response to Ag.

Inhibition of bovine peripheral blood mononuclear cell blastogenesis by fractionated mammary secretion

1. Bovine mammary secretion whey obtained during late involution markedly inhibited mitogen-induced blood mononuclear cell blastogenesis. 2. Whey proteins eluting in the first and second absorbance peaks following molecular exclusion chromatography were associated with greatest inhibition of mononuclear cell blastogenesis. 3. Greatest inhibition of concanavalin A-stimulated mononuclear cell blastogenesis was associated with high concentrations of whey proteins in absorbance peak 1. 4. Whole mammary secretion whey and whey proteins in absorbance peak 2 caused similar inhibition of concanavalin A- and phytohaemagglutinin-treated mononuclear cells. 5. Differential inhibition of mitogen-induced blastogenesis may reflect the presence of immunosuppressive substances in bovine mammary secretion whey which differ in specificity for bovine T-cell subsets.

Isolation and characterization of a T-suppressor factor specific for the lupus-associated autoantigen RNP-Sm

We have previously described a monoclonal antibody, B16G, which has been found to be specific for T-cell derived suppressor factors (TsF). B16G has been shown to react with T-suppressor cells, TsF in the spleen of normal or tumor-bearing mice, the TsF produced by tumour-specific, or hapten-specific T-cell hybridomas, and with polyclonal whole human TsF isolated from tonsillar tissue. This pan-reactivity inherent to the B16G antibody suggests that it recognizes some common, shared epitope of the TsF molecule. In this study, we have used B16G as a probe to isolate a TsF-producing T-cell hybridoma, S-50, from CBA mice (H-2k) that is specific for the Lupus-associated antigen, RNP-Sm. The TsF bound specifically to RNP-Sm and inhibited the production of anti-RNP-Sm antibody cell cultures from MRL-lpr mice. SDS-PAGE analysis of purified S-50 TsF revealed a B16G-reactive band with a molecular weight of 43 kd.

Active suppression of host-vs graft reaction in pregnant mice. IX. Soluble suppressor activity obtained from allopregnant mouse decidua that blocks the cytolytic effector response to IL-2 is related to transforming growth factor-beta

Non-Ts cells in murine allopregnancy decidua release potent immunosuppressor factors in vitro that block the action of IL-2. Previous studies have shown that both primary and secondary CTL responses are inhibited as well as the generation of Il-2 activated killer cells. In this paper we show that the suppressor factor(s) can arrest ongoing IL-2 dependent CTL responses but does not block binding of anti-IL-2R antibody or radiolabeled IL-2 to the IL-2R. The suppressive activity is associated with molecules that adhere to hydroxylapatite and con A-agarose but do not bind to activated charcoal or partition as lipids. HPLC TSK 3000 separation showed a major peak of suppressive activity at 60 to 100 kDa, with additional activity at 300 kDa, and at less than 1000. Under acid conditions, suppressive activity resolved as a major peak at 13 kDa with some residual activity at 65 kDa and at less than or equal to 1000. A specific rabbit IgG antibody to transforming growth factor-beta neutralized suppressor activity in unseparated supernatant and in the 13-kDa fraction whereas neutralizing antibodies to progesterone or PGE-2 did not affect suppression but could neutralize their respective ligands. Inasmuch as transforming growth factor-beta has a 25 kDa Mr, the 13-kDa decidua-associated suppressor factor would appear to represent a related but distinct regulatory molecule that associates with a variety of carrier molecules.

Delineation between T- and B-suppressive molecules from human seminal plasma: I. Partial characterization of a 180-kD protein inhibiting the B response to T-independent antigens

The immunosuppressive activity of fractionated human seminal plasma (SP) was investigated both in vitro (on human lymphocytes) and in vivo with Balb/c mice. SP fractionation by dialysis allowed delineation of the major suppressor factors according to their respective sizes--small (less than 12 kD) or large (greater than 12 kD). In vitro, large molecules were found to suppress the B-cell proliferative response induced by the Nocardia mitogen, while small molecules suppressed the T-cell proliferation induced by phytohemagglutinin. In vivo, immunosuppression was obtained almost exclusively on T-independent responses after preliminary treatments either with unfractionated SP or with large SP molecules. Both type 1 and type 2 T-independent responses were suppressed, as evidenced by plaque-forming cells and antibody assays. In contrast, no immunosuppression was found in vivo after treatment by small SP molecules. Purification of the B-cell suppressor by gel filtration and high-performance liquid chromatography, as well as by preparative isofocusing, indicated that its molecular weight was 180 kD and its isoelectric charge was between pH 5 and 6. This factor is a protein, as evidenced by pronase digestion. A possible role for this molecule in the protection of sperm against the female immune system is discussed.

Hydatidiform mole macromolecules inhibit interleukin-2-mediated murine lymphocyte proliferation in vitro

Macromolecules extracted from hydatidiform mole trophoblast inhibit mitogen-induced lymphocyte proliferation. To characterize the mechanism of this immunomodulation, we determined the effects of hydatidiform mole vesicle fluid (HMF) and tissue extracts (HME) on lymphokine function in vitro. Utilization of interleukin-1 (IL-1) and interleukin-2 (IL-2) were determined by using a lymphoma cell line (LBRM-33-1A5) and a murine T cell line (CTLL2), respectively. HMF suppressed (P less than .05) IL-2-dependent CTLL2 cell proliferation at 500 (36.4% of controls) and 50 (74.9% of controls) micrograms/ml. HME also suppressed CTLL2 proliferation (P less than .05) at 500 (46.0% of controls), 100 (67.2% of controls), 50 (71.5% of controls), and 10 (85.4% of controls) micrograms/culture ml. In contrast, HMF exhibited no effect on IL-1-stimulated LBRM-33-1A5 production of IL-2. However, 500 micrograms/ml of HME inhibited (P less than .05) IL-2 production (63.0% of controls) in the IL-1 utilization assay. This suppressive effect was probably due to a carry over of HME from the LBRM-33-1A5 culture to the target cells (CTLL2) used to measure IL-2 production. Molecular weight chromatography of an HME sample eluted an IL-2 inhibitor in a low molecular weight (35-50 kd) and high molecular weight (greater than 250 kd) fraction. These data suggest that one way in which macromolecules derived from hydatidiform mole could interfere with in vitro immunologic responses is by modulating interleukin-2 function.

The response of human marrow colony-forming units-granulocyte and macrophage to inhibition by prostaglandin E and acidic isoferritins is associated with expression of MHC class II antigens and requires the participation of a CD8+ T lymphokine

The in vitro expression of MHC class II Ag by human bone marrow colony-forming unit-granulocyte and macrophage (CFU-GM) and their proliferative response to negative growth regulators in agar culture are transient and can be modulated in vitro by 24-h suspension culture in the presence of PGE. Analysis of the participation of accessory cells in this phenomenon indicates that the ability of PGE to modulate CFU-GM MHC class II expression, the proportion of CFU-GM in S-phase of the cell cycle and the responsiveness of CFU-GM to inhibition in vitro by two negative growth regulators, acidic isoferritin inhibitory activity and PGE itself, requires the participation of CD8+ T lymphocytes. This effect is mediated by a lymphokine of m.w. 27,000 that we have purified to apparent homogeneity. This lymphokine possesses neither colony stimulatory nor inhibitory activity, is produced by both peripheral blood and bone marrow CD8+ T lymphocytes, as well as the CEM T-ALL cell line, and requires the obligatory presence of PGE for activity.

Suppressive substance produced by T cells from mice chronically infected with Trypanosoma cruzi. III. Genetic restriction and further characterization

Earlier papers in this series reported that the culture supernatant of splenic L3T4+, Lyt-2- T cells from susceptible CBA mice chronically infected with Trypanosoma cruzi contain a SS3 that can inhibit the induction of delayed-type hypersensitivity to a wide range of Ag. The SS is a glycoprotein with an apparent molecular mass of 30 to 60 kDa and is distinct from T. cruzi Ag, IL-1, IL-2, IL-3 or IFN-gamma. It also has no effect on Th cells for antibody, cytotoxic T cells or immediate-type hypersensitivity. In this paper, we report that SS can suppress the induction of proliferating T cells but not the presentation of Ag to a cloned T cell line (D10). It also has no effect on the induction of delayed-type hypersensitivity in vitro. SS is produced by a number of inbred mouse strains irrespective of their susceptibility to infection with T. cruzi (BALB/c, highly susceptible; CBA, susceptible; C57BL/10, resistant) but only CBA mice are sensitive to the suppressive action of SS. This is so whether the SS is derived from CBA, BALB/c, or C57BL/10. The sensitivity to SS is not a feature of the H-2k haplotype inasmuch as B10.BR and BALB/k mice (also H-2k) do not respond to SS. Attempts to purify SS with a range of biochemical techniques substantially enriched the specific activity but failed to produce a substance visualizable by analytical gel electrophoresis. IEF chromatography revealed SS activity spanning a pH range from 6 to less than 4. This suggests that SS is likely to be a minor heterogeneous component of the suppressive supernatant. The genetically highly restricted nature of its action is intriguing and may explain some of the contradictory reports in the literature on this subject.

Human immunodeficiency virus-induced cytotoxicity for CD8 cells from some normal donors and virus-specific induction of a suppressor factor

Several aspects of human immunodeficiency virus (HIV)-induced pathology in vitro warrant close examination to ascertain their role in the development of disease in vivo. The ability of HIV to produce cytopathology of CD4 cells has been well documented, although the extent and mechanism(s) may be varied. Further, immune suppression by HIV envelope (env) is well documented in vitro, but its importance in vivo remains unknown and the role of other HIV components in immune suppression has not been examined. We have exposed peripheral blood mononuclear cells (PBMC) from normal donors to ultraviolet-irradiated HIV (uv-HIV) at concentrations similar to those found in AIDS patient serum and determined that in some normal donors (3/7) depletion of CD8 cells as well as CD4 cells is demonstrable. Abrogation of phytohemagglutinin (PHA)-induced proliferation by uv-HIV was also examined in the same normal donors. Immune suppression, unlike CD4 cell killing, does not require intact virus and occurs at physiologically relevant concentrations of HIV. Furthermore, PBMC exposed to uv-HIV in the presence of PHA produce a heat- and protease-labile suppressor factor(s) following removal of virus, whether or not they are reexposed to PHA. Our results suggest that cell killing may be a more broad event than previously described, including the killing of at least CD8 cells either directly or indirectly. In addition, suppressor factors produced following exposure of patient lymphocytes to agents that induce proliferation may exacerbate the development of opportunistic infection.

Immunosuppressive effects of rabbit blastocoelic fluid and embryo culture medium

In order to understand the mechanism of the feto-maternal immune relationship, we assayed the immunosuppression activities of fresh blastocoelic fluid and decomplemented peripheral serum collected from day-9 pregnant white New Zealand rabbits and of rabbit embryo culture medium (ECM). Because the viability of the human lymphocytes was not affected by either of these biological fluids and since they were easy to obtain in sufficient quantities, they were used uniformly in all the experiments. Immunosuppressive effect was calculated by the relative inhibition of proliferation of Con A-stimulated lymphocytes. The immunosuppressive effect of blastocoelic fluid of the 9-day pregnant rabbits was significantly higher than that of autologous decomplemented serum (P less than 0.001). The inhibition by the serum was non-specific because sera from non-pregnant animals as well as sera from different stages of pregnancy and pseudo-pregnancy showed the same level of inhibition. The ECM of 6.5-7-day-old embryo showed a pronounced immunosuppressive effect. When embryos of 1,3 and 5 days were cultured and their culture media were assayed only with 5-day-old embryo the effect had begun to appear, but it was far less than that of 7-day-old embryo (P less than 0.02). The suppressive activity of both the blastocoelic fluid and ECM was not due to cytotoxic effect, since this fluid supported the in vitro growth of single-cell rabbit embryos up to the stage of blastocyst. These results suggest that the immunologic tolerance of the embryo might be due to the immunosuppressors secreted by the embryo and that there might be a localized effect at the implantation site rather than a maternal systemic immunosuppressive effect.

Purification and characterisation of an immunosuppressive factor from normal human seminal plasma

We have previously described the presence of a human seminal plasma component which may prevent the immunologic sensitization of females against sperm and seminal plasma antigens. Purification of the immunosuppressive factor (ISF) by saturated ammonium sulphate precipitation, followed by Sepharose 4-B column chromatography and Con-A Sepharose 4-B affinity chromatography is described here. An apparently single-band protein on SDS gel electrophoresis, having a molecular weight of 35,000, has been isolated. Amino acid analysis of this glycoprotein shows that it is rich in isoleucine, glycine, glutamine and proline, while methionine, tyrosine and asparagine are present in traces.

Antigen-specific immune-suppressor factor in herpes simplex virus type 2 infections of UV B-irradiated mice

UV B-irradiation (280 to 320 nm) of mice at the site of cutaneous infection with herpes simplex virus type 2 (HSV-2) induced suppressor T-cell circuits that decreased HSV-2-induced proliferative responses of HSV-2-immune lymph node cells. Adoptive transfer experiments indicated that splenocytes from UV B-irradiated HSV-2-infected animals contain L3T4+ cells that suppress proliferative responses in vivo, consistent with suppressor inducer cells. However, following in vitro culture of the splenocytes with HSV-2 antigen, the proliferation of immune lymph node cells was inhibited by Lyt2+ suppressor T cells, consistent with antigen-induced suppressor effector cells. Antigen-specific and nonspecific suppressor factors were fractionated from supernatants of HSV-2-stimulated spleen cells by molecular-sieve chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the Sephadex fraction that contained the antigen-specific suppressor factor, in the presence or absence of 2-mercaptoethanol, defined a 115-kilodalton protein consisting of two disulfide-bound components with molecular sizes of 70 and 52 kilodaltons. The implications of these results with respect to the regulation of HSV-induced cell-mediated immunity following UV B-irradiation are discussed.

Partial purification and characterization of systemic lupus erythematosus derived factors that suppress production of interleukin-2

We report here on interleukin-2 (IL-2) suppressive factors, synovial fluid (SF) peripheral blood mononuclear cells (PBM), derived from short term cultures of unstimulated PBM of patients with systemic lupus erythematosus (SLE). SF PBM suppressed production of IL-2, but not proliferative responses to this lymphokine. It was sensitive to acid (pH 2.6), heat (56 degrees C), and tryptic digestion. It retained activity in the presence of 2-mercaptoethanol (2-ME), had no interferon activity and no non-specific cytotoxicity. Although crude SF PBM contained IgG and PGE2, these were not associated with its 2 active fractions. SF PBM was partially purified on a G-200 Sephadex column. IL-2 suppressive activity was detected in 2 fractions of molecular weights corresponding to greater than 150 kD and 40-60 kD, the latter acting only in the presence of monocytes. SF PBM appear to affect directly the IL-2 producer cell, since it suppressed IL-2 production by (1) mitogen stimulated PBM depleted of CD8+ suppressor cells and by (2) mitogen induced Jurkat cells. These "spontaneous" suppressive factors were ubiquitous in SLE, and may be important tools for studying the defective IL-2 production in SLE and its significance in the development of the disease.

Identification of two species of suppressive factor of differing molecular weight released by in vitro fertilized human oocytes

Preimplantation human embryos have been shown to release factors that have immunosuppressive activity and that are highly correlated with successful implantation. The present study was undertaken to determine the molecular weight of these factors using HPLC. Two peaks of suppressive activity were found associated with molecular weights of 3.7 +/- 0.3 and 1.2 +/- 0.1 kd, respectively. The potential significance of low molecular weight immunosuppressor factors in avoiding maternal inflammatory and immunologic responses is discussed.

Purification to homogeneity and biochemical characterization of two suppressor factors from human malignant T-cells

A cell clone (GI-CO-T-9) derived from a long term T-cell culture (PF-382), established from a patient affected by acute T-lymphoblastic leukemia (T-ALL), was selected for the presence in the culture medium of factors suppressing T-cell proliferation. The crude supernatant has been subjected to a multi-step chromatographic fractioning, including: preparative gel permeation, anion exchange, and hydrophobic interaction High Performance Liquid Chromatography (HPLC). The highly purified material was characterized by polyacrylamide gel electrophoresis in sodium dodecyl sulfate (SDS-PAGE), revealing single bands of 115 Kd and 80 Kd. The isoelectric points (pI), determined by flat-bed isoelectric-focusing, were 7.4 for High Molecular Weight Suppressor Factor (HMWSF) and 3.5-3.6 for Low Molecular Weight Suppressor Factor (LMWSF).

Partial characterization of suppressor factors in spleen cell culture supernatants of Mycobacterium lepraemurium-infected mice

Suppressor factors (SF) were released into the culture supernatant when spleen cells from M. lepraemurium-infected C57BL/6 mice were incubated at 37 degrees C in the absence of any inducing agents. Some of the SF appeared to be specific in that they inhibited the blastogenic response to mycobacterial antigens by opposition to the others which inhibited the blastogenic responses to PHA, Con A and LPS. All SF seemed to be produced in a cyclic manner. In mice infected 9 weeks earlier, the release of "specific" SF occurred early (4-8 h) during the incubation period whereas, the nonspecific SF were released later on (12-32 h). Adoptive transfers of SF-containing culture supernatants depressed the expression of DTH to M.1m antigens but not its induction.

Human seminal plasma suppresses lymphocyte responses in vitro in serum-free medium

The in vitro immunosuppressive properties of human seminal plasma have been re-investigated in serum-free medium in view of recent suggestions that the previously observed effects might be dependent on the presence of exogenous serum co-factors present in the culture media. The present studies reveal that low concentrations of seminal plasma can inhibit the ability of peripheral blood leukocytes to lyse K562 target cells in the absence of fetal calf or new-born calf serum. These inhibitory effects could be achieved by pre-incubating the effector cells in seminal plasma at 37 degrees C prior to use in the natural killer cell assay or by incorporating it into the assay system. Additional studies revealed that human seminal plasma could also inhibit the proliferative response of peripheral blood lymphocytes to phytohaemagglutinin in serum-free HB103 medium. These effects were most marked and consistent if the seminal plasma was present throughout the period of culture. Overall, these studies indicate that the previously reported suppressive effects of human seminal plasma in these systems cannot be entirely attributable to cytotoxic factors generated by exogenous serum components.

Generation and activity of suppressor peptides following traumatic injury

Severe trauma is known to produce pathophysiologic changes leading to the generation of immunosuppressive compounds. With recent advances in biotechnology, a number of these factors have been identified and characterized. Many of these substances have been found to be degradation products of normal serum and tissue proteins. These degradation products have profound biologic activity both in vivo and in vitro. This report briefly focuses on a number of these factors and summarizes the current work involved in the determination of the identity and mechanisms of a previously reported suppressor-active peptide isolated from the serum of trauma patients.

Suppressive substance produced by T cells from mice chronically infected with Trypanosoma cruzi. I. Preferential inhibition of the induction of delayed-type hypersensitivity

Culture supernatants of spleen cells from susceptible CBA mice chronically infected with Trypanosoma cruzi were able to inhibit the induction of delayed-type hypersensitivity (DTH) to a wide range of antigens as measured by 24-hr footpad swelling, bone marrow homing, and radioactivity accumulation assays. The suppressive activity, which was also present in the serum of these chronically infected mice, appears to be specific for the induction of DTH and had no effect on the 3-hr immediate-type hypersensitivity. It also failed to modify the expression of DTH in presensitized mice. Furthermore, it did not affect the synthesis in normal recipients of specific antibody or the induction of helper T cells or cytotoxic T cells. It also failed to induce DTH tolerance as recipient mice with markedly reduced DTH were able to develop a normal DTH response after secondary immunization. The suppressive activity was produced by an Ig- macrophage-depleted splenic T cell population, whose capacity to secrete the suppressive substance was completely abrogated by treatment in vitro with anti-L3T4 antibody and complement, but not with anti-Lyt-2 antibody and complement. These results therefore demonstrate that L3T4+ T cells from mice chronically infected with T. cruzi can produce substances which interfere with the induction of DTH. This finding may help to identify the differential antigenic stimulatory requirement for the activation of the various subsets of T cells.

Murine interstitial nephritis. VII. Suppression of renal injury after treatment with soluble suppressor factor TsF1

We prepared soluble suppressor T cell factor (TsF1) from donor spleens harvested from mice primed with tubular antigen-derivatized lymphocytes to analyze both its functional interactions with a larger suppressor T cell network and its influence on the nephritogenic effector T cell response producing interstitial nephritis to a parenchymal antigen. Our findings indicate that TsF1 is antigen-specific, genetically restricted by I-J in its direct mediation of suppression, and capable of inhibiting the development of interstitial lesions. TsF1 also provides an inducing signal for the activation of effector Ts-2 suppressors following presentation by accessory cells. The induction of a Ts-2 effect, however, requires that the factor-presenting cell and the recipient of such cells share homology at I-J, and that the TsF1, the precursor Ts-2 cells, and the recipient of the Ts-2 effect share the same Igh-V allotype. Finally, the results of this current report clearly demonstrate a possible therapeutic role for soluble suppressor factors in the management of interstitial renal disease.

Isolation of an antigen-specific T suppressor factor that suppresses the in vivo response of DBA/2 mice to ferredoxin

A T cell hybridoma (Fd11) has been produced from B10.D2 mice that secretes a putative antigen-specific T suppressor factor (TsF). The TsF is isolable from culture supernatants of Fd11 by affinity purification over columns containing either a monoclonal antibody (B16G) shown previously to be capable of binding murine TsF or ferredoxin (Fd), the nominal antigen to which the Fd11 TsF binds. Specificity of the Fd11 TsF for Fd was established by comparing it to another TsF isolated by us (A10 TsF) in a sandwich ELISA, and by demonstrating the specific reactivity to Fd of the hybridoma in calcium flux studies. The Fd11 affinity-purified TsF was shown to contain two major unique components with m.w. in the region of 80,000 and 35,000 when run on reducing polyacrylamide gels in the presence of sodium dodecyl sulphate. Specific immunosuppressive properties of Fd11 were demonstrated when Fd11 TsF (10 micrograms) was injected i.v. into Fd-primed syngeneic mice at the time of antigen boost. Fd11 TsF specifically and significantly diminished the secondary antibody response to Fd in DBA/2 mice.

Soluble factors secreted by naturally occurring suppressor cells that interfere with in vivo graft-vs.-host disease and with T cell responsiveness in vitro

A potent immunosuppressive factor (SUF) is found in the supernatant of short-term cultures of unstimulated thymocytes or spleen cells of neonatal mice and rats and in culture medium of hybridoma cell lines established by fusing neonatal mouse spleen cells with T lymphoma cells (the BW 5147 line). In vitro incubation of spleen cells with SUF suppresses the acute in vivo graft-vs.-host disease, normally induced by allogeneic spleen cells in lethally irradiated mice. Incubation of bone marrow cells with SUF does not affect the hemopoietic stem cells. The addition of SUF to mixed lymphocyte reaction cultures strongly suppresses lymphocyte proliferation. The non-species-restricted inhibition of cell proliferation induced by SUF is shown not to be due to toxicity or nonspecific interference with DNA synthesis. Molecular size fractionation of crude SUF revealed two active moieties: a large moiety of molecular mass greater than 100 kDa and a small moiety of less than 3 kDa. The high kDa moiety mediates T cell unresponsiveness both in vivo and in vitro. In vitro studies revealed that this moiety primarily affects an early event in the proliferative response to alloantigen and mitogen, that prevents interleukin 2 (IL 2) receptor expression and, consequently, blastogenesis and DNA duplication. It does not affect, however, the synthesis of IL 2. The suppressive activity of the low kDa moiety can be demonstrated only in in vitro systems. Pre-treatment of donor lymphocytes with this fraction cannot prevent graft-vs.-host disease mortality. The inhibition of cell proliferation induced by this fraction in vitro is most likely due to interference with the utilization of IL 2, as suggested by its suppressive effect on the proliferation of CTLL-2 cells (an IL 2-dependent cell line).

T cell suppressor factor from human glioblastoma cells is a 12.5-kd protein closely related to transforming growth factor-beta

T cell suppressor factor produced by human glioblastoma cells inhibits T cell proliferation in vitro and more specifically interferes with interleukin-2 (IL-2)-dependent T cell growth. Here we report the purification of this factor from conditioned medium of the human glioblastoma cell line 308. Amino-terminal sequence analysis of the 12.5-kd protein demonstrates that eight out of the first 20 amino acids are identical to human transforming growth factor-beta. Purified glioblastoma-derived T cell suppressor factor and transforming growth factor-beta from porcine platelets inhibit both IL-2-induced proliferation of ovalbumin-specific T helper cells and lectin-induced thymocyte proliferation with similar specific activities. If released by glioblastoma cells in vivo, the factor may contribute to impaired immunosurveillance and to the cellular immunodeficiency state detected in the patients.

A functional idiotypic network of T helper cells and antibodies, limited to the compartment of "naturally" activated lymphocytes in normal mice

As shown previously, idiotype (Id) sharing between anti-2,4,6-trinitrophenyl T helper (Th) cells and antibodies in BALB/c mice results from immunoglobulin (Ig)-dependent selection of the T cell repertoire. In contrast, a clonotype defined by the same F6(51) anti-Id antibody is expressed by C57BL/6 anti-(4-hydroxy-3-nitrophenyl)acetyl Th cells independently of Ig influences. We have now used these systems to test the hypothesis that Ig-dependent Th cell repertoire selection occurs in the compartment of "naturally" activated lymphocytes. "Naturally" activated or resting splenic L3T4+ cells were separated from normal BALB/c and C57BL/6 mice and tested, either directly or after in vitro priming, in hapten-specific helper assays for expression of the clonotope defined by the F6(51) anti-Id antibody. The results show the selective expression of the antibody-dependent T cell Id in the "naturally" activated helper cell compartment. In contrast, when the T cell Id is expressed in the absence of Ig-dependent selection, it is only detected in the resting helper cell repertoire. Furthermore, BALB/c "natural" IgM antibodies with anti-Id specificities similar to F6(51) show functionally relevant interactions with syngeneic "naturally" activated Th cells. These are also characterized by high paratopic/Id degeneracy, as compared to helper cells obtained by conventional immunization. These results demonstrate repertoire differences between the set of (resting) lymphocytes participating in immune responses, vs. those "internally" activated in normal individuals. They also suggest the importance of Id network interactions in the compartment of "naturally" activated T and B cells.

An evaluation of the existence of soluble suppressor factors in cloned antigen-specific T suppressor lymphocytes

The suppressive activity of two bovine serum albumin-specific class II-restricted T suppressor cell clones (BVI/5 and 83/2-D11) was compared to that of a feeder cell-independent, IL 2-dependent subline (HF1.IL-2) of an originally antigen-dependent class II-restricted Ts cell clone (HF1). No soluble suppressor factors can be found in BVI/5 and 83/2-D11 Ts cell extracts or culture supernatants under conditions where an unspecific factor can be derived from HF1.IL-2 cells. This factor, when isolated from cell extracts in the presence of n-octyl-beta-D-glycopyranoside, has a molecular weight of 70-80 kD. In absence of this non-ionic detergent, it has a high affinity to membrane fragments and is associated with a molecular weight of 300 kD or more. The data are discussed in connection with recent findings of direct T suppressor to T helper interaction by cell-cell contact.

Serum-mediated suppression of lymphocyte transformation responses in coccidioidomycosis

Lymphocyte transformation (LT) responses to coccidioidin (CDN) and spherulin were suppressed in 11 (73%) of 15 patients with active coccidioidomycosis when their mononuclear cells were assayed in autologous serum as compared to serum from healthy, CDN skin test-positive subjects. Suppressed LT responses were specific for Coccidioides immitis antigens in 7 (64%) of the 11 patients. Immunoaffinity chromatography of patient sera with Staphylococcus protein A adsorbed the suppressor component(s) and thereby established that suppression was attributed to immunoglobulin G, either alone or complexed with antigen. The possibility that suppression was mediated by immune complexes was examined by adding complexes formed in vivo or in vitro to mononuclear cell cultures of healthy CDN-reactive persons before LT assays. Although complexes prepared in this manner were reactive in an enzyme-linked immunosorbent assay designed to detect Coccidioides antigen-specific immune complexes, no suppression of LT responses was observed. We conclude that serum-mediated suppression of LT responses in coccidioidomycosis is attributed to monomeric and not immune-complexed immunoglobulin G antibody.

Purification and partial biochemical characterization of IgE-binding factors secreted by a human B lymphoblastoid cell line

IgE-binding factors (IgE-BFs) were purified from the culture supernatant of RPMI-8866 cells, a human lymphoblastoid B-cell line expressing IgE receptors. The material, purified by affinity-chromatography on immunoadsorbents coupled to IgE or to monoclonal antibody against IgE receptor, was comprised of two major components with apparent molecular weight (MW) of 25,000-27,000 and 12,000, as determined by SDS-PAGE and silver staining. Only the 25,000-27,000 MW molecules were identified as IgE-BFs, as demonstrated by their reactivity with MabER in the Western blot and the immunoprecipitation assays, and their ability to inhibit rosette formation of U937 cells with IgE- but not with IgG-coated erythrocytes. IgE-BFs were purified to homogeneity by combining affinity-chromatography and either DEAE-ion exchange or reverse-phase chromatography on an HPLC system. Chromatofocusing analysis demonstrated the microheterogeneity of IgE-BFs that were comprised of molecules with isoelectric points ranging from 5.0 to 4.4. IgE-BFs were sensitive to treatment with O-glycosidase but not with N-glycanase. These molecules were resistant to heat and to pH ranging from 2 to 9; their immunoreactivity was lost after treatment with trypsin and pepsin. Papain digestion of purified IgE-BFs generated 14,000-16,000 MW molecules that were still binding to IgE and to MabER.

Characterization of monoclonal nonspecific suppressor factor (MNSF) with the use of a monoclonal antibody

The secretion of immunoglobulin (Ig) from cultured mononuclear cells by lipopolysaccharide (LPS) stimulation is inhibited by monoclonal nonspecific suppressor factor (MNSF), a lymphokine produced by murine T cell hybridoma. In an attempt to develop a murine monoclonal antibody (MAb) with specific reactivity against MNSF, a cell fusion technique that incorporated immune murine splenocytes and HAT-sensitive murine myeloma cells was used. Cross-reactivity experiments confirmed that the MAb (MO6) does not bind to unrelated proteins such as bovine serum albumin, mouse IgG, and murine interferon-gamma (IFN-gamma). There are no effects when anti-IFN-gamma antibodies are used with MNSF. As far as biological activity is concerned, MO6 inhibits in vitro the activity of MNSF in terms of the Ig secretion from cultured lymphocytes. By using MO6, affinity chromatography and immunoblotting were performed. The MNSF on the SDS-PAGE showed a band with m.w. of approximately 70,000, indicating the formation of an aggregate in saline; but after treatment with 0.4 M pyridine-acetic acid buffer, separate bands of 24,000 and 16,000 daltons were evident. Therefore MO6 recognizes 70,000 and both 24,000 and 16,000 daltons. Thus we confirmed by using this MAb and affinity chromatography, the existence of human counterpart, human nonspecific suppressor factor (hNSF), in supernatant from concanavalin A-stimulated T cells. When hNSF was fractionated by high pressure liquid chromatography (HPLC), the activity was found in a region corresponding to 70,000 daltons. However, when fractionated in pyridine-acetic acid buffer, hNSF activity was distributed in a slightly wider range of 15,000 to 30,000 daltons. Physicochemical analysis showed that the purified hNSF is resistant to either heating at 56 degrees C or to 2-mercaptoethanol treatment; however, it is labile to acidification at pH 2.0 and is also sensitive to protease treatment, the characteristics of which were similar to those of murine MNSF. Thus MO6 was confirmed to be a pertinent tool for isolation of hNSF, as well as for murine MNSF.

Immunoregulatory factor released from a cell line derived from human decidual tissue

The culture supernatant of the TTK-1 cell line, established from human decidual tissue, was found to contain a factor that strongly suppressed the mixed lymphocyte reaction (MLR). The mechanism of the MLR-suppressive activity as well as the biochemical characterization of this factor was analyzed. The TTK-1 supernatant suppressed the MLR much more strongly than the culture supernatants of the three other malignant cell lines examined. The molecular weight of this factor was estimated to be between 43 kilodaltons (kd) and 67 kd by gel filtration chromatography. The TTK-1 supernatant also suppressed the proliferation of the interleukin 2 (IL-2)-dependent T cell lines, but did not suppress that of the IL-2-independent T cell lines, suggesting that the TTK-1 supernatant inhibited the action of IL-2 and subsequently suppressed the MLR. The fact that the TTK-1 cell line originated from human decidual tissue might imply the important role of this factor in immunological fetomaternal balance.

Spontaneous production of a suppressor factor by a human macrophage-like cell line U937. II. Suppression of antigen- and mitogen-induced blastogenesis, IL 2 production and IL 2 receptor expression in T lymphocytes

U937, a human macrophage-like cell line, spontaneously produces a factor which inhibited blastogenic responses of human blood T lymphocytes stimulated with tuberculin-purified protein derivative (PPD) or phytohemagglutinin (PHA). We investigated the mechanism of suppressor action of the U937 factor. The U937 suppressor factor inhibited interleukin 2 (IL 2) production by human blood T lymphocytes stimulated with PPD or PHA. IL 1 did not overcome the inhibitory action of the U937 factor on PPD-induced IL 2 production by human blood T lymphocytes. The U937 factor also inhibited the production of IL 2 by a human leukemic cell line, JURKAT, stimulated with PHA. The U937 suppressor factor interfered with the expression of Tac antigen (IL 2 receptor) on PPD- or PHA-stimulated blood T lymphocytes. The inhibitory activity of the U937 factor on Tac expression was not affected by the addition of IL 2 or a crude lymphokine-containing T cell supernatant. Tac expression was more sensitive than IL 2 production to inhibition by U937-conditioned medium. The U937 suppressor factor was precipitable by 33 to 67% saturated ammonium sulfate and was inactivated at pH 2 or pH 11. Sephacryl S-200 Gel filtration analysis of U937 culture supernatants revealed that the inhibitory activities for blastogenesis, IL 2 production, and Tac expression co-purified in fractions with an apparent m.w. between 67,000 and 130,000. These data indicate that U937 spontaneously produces a macromolecular suppressive factor with major locus of action on the production of IL 2 and the expression of the IL 2 receptor.

Depression of cell-mediated immunity by tumour cell products: induction of resistance by immunotherapeutically active extracts of bovine ocular squamous cell carcinoma

Tumours produce substances that inhibit the expression of cell-mediated immunity, in the form of delayed-type hypersensitivity in mice. Phenol-saline extracts of bovine ocular squamous cell carcinoma (BOSCC) which have immunotherapeutic activity in cattle were able to immunize mice against this depressive effect. Such immunization was effective against products of BOSCC, a spontaneous rat tumour, three of four human tumour cell lines and (in other experiments) mouse tumours. Phenol-saline extracts of mouse tumour cell lines were immunogenic (protective against depression of delayed-type hypersensitivity) in mice. Fractions of BOSCC phenol-saline extracts which were immunotherapeutically active in cattle were generally also protective in mice. The protective activity was lost after treatment with proteinase K, and was present in the supernatant after precipitation with 55% ammonium sulphate. It was not affected by treatment with RNase or DNase or by heating to 50 degrees C for 2 h. It was present in gel filtration fractions with an apparent molecular weight of 10,000-37,000 daltons. The immunogenic factor in mice and the immunotherapeutic factor in cattle may be related to each other.

Characterization of Japanese encephalitis virus-specific suppressor T cells and their product in suppression of the humoral immune response in mice

Since Japanese encephalitis virus (JEV) induces the generation of suppressor T cells in mouse spleen which, through the production of a soluble suppressor factor (SF), suppress IgM plaque-forming cells (IgM-PFC) the present study was undertaken to further characterize these suppressor cells and the SF. The suppressor cells were Ly1-2+ and sensitive to hydrocortisone and a high dose of irradiation. SF was trypsin-sensitive, thermolabile and non-dialysable, and passed through a 450-nm filter. This SF was shown to be a low molecular weight substance, with an approximate MW of 18,000 daltons.

Isolation of functional polyclonal TsF from MRL-lpr spleens using monoclonal antibody absorbance

We have previously described a monoclonal antibody, B16G, which has been found to be specific for T-cell derived suppressor factors (TsF). B16G has been shown to react with T-suppressor cells, TsF in the spleens of normal or tumor-bearing mice, the TsF produced by a tumor-specific T-cell hybridoma, and with polyclonal whole human TsF isolated from tonsilar tissue. This panreactivity inherent to the B16G MAb has made it clear that it recognizes some common, shared epitope of the TsF molecule. In this study we have used B16G as a probe to isolate TsF from the spleens of MRL-lpr mice and compare the activity with these factors isolated from the spleens of an MHC compatible nonautoimmune strain, CBA. We find that equivalent quantities of functional TsF are isolable from both strains and thus, it can be concluded that the associated oligoclonal B-cell activation characteristic of MRL-lpr mice is not due to a polyclonal T-suppressor cell deficit, nor to the ability of TsC in these mice to produce soluble, functional TsFs. The molecular and biochemical characteristics of these TsFs are discussed.

Inhibition of interleukin 1 activity by a factor in submandibular glands of rats

With the sequential use of ammonium sulfate precipitation, gel filtration and chromatofocusing, we have partially purified from extracts of the submandibular glands of rats a factor (referred to as submandibular gland's immunosuppressive factor or SMG-ISF) capable of inhibiting the in vitro proliferation of mitogen- and antigen-stimulated murine lymphocytes. The semi-purified suppressor fractions had an isoelectric point of 4.4 to 4.5 and consisted of at least three molecular species. These active fractions suppressed the mitogenic effects of Concanavalin A phytohemagglutinin, and lipopolysaccharide. In vitro immune reactions such as the mixed lymphocyte culture MLC reaction and the production of cytotoxic T lymphocytes (CTL) across major histocompatibility barriers in mice were also suppressed. These in vitro immunosuppressive effects required the addition of the suppressor fractions early after the initiation of the cultures and were reversed if the factor was removed from the cultures at least 48 to 72 hr before the completion of the assays. The active fractions did not affect the proliferation of CTLL 2 cells induced by interleukin 2 (IL 2), but inhibited the mitogenic and co-stimulatory effects of IL 1 on mouse thymocytes, and in this effect showed a dose-response relation suggestive of a competitive mechanism. These characteristics of SMG-ISF indicate a specific inhibition of the activity of IL 1.

Characterization of an immunosuppressive factor from malignant ascites that resembles a factor induced in vitro by carcinoembryonic antigen

Oncodevelopmental antigens may cause immunologic suppression in the host through release of suppressor molecules from the host's own immunoregulatory cells. This concept has been difficult to study until recently when carcinoembryonic antigen was shown to induce the release of such molecules from normal circulating human mononuclear cells in vitro. However, the amount of the suppressor moiety generated was too small to adequately characterize, and its presence in vivo, i.e., in the cancer-bearing host, was unknown. Therefore, we sought to isolate and characterize a similar or identical macromolecule from ascites having an elevated CEA level in patients with cancer. A single malignant ascites, when precipitated at 0 to 35% ammonium sulfate saturation, was the source of suppressive factor for purposes of isolation and standardization. Suppression was quantitated by reduction of [3H]thymidine incorporation by phytohemagglutinin-stimulated normal human peripheral blood mononuclear cells. Sephadex G-200 chromatography revealed probable aggregation of the factor in isotonic buffers; aggregation was reduced in the presence of 8 M urea. Purification was achieved by precipitation with 5% trichloroacetic acid (TCA). The suppressor factor remained soluble in TCA and demonstrated a 95-fold increase in specific activity. Analytical sodium dodecyl sulfate polyacrylamide gel electrophoresis demonstrated a single protein band of 50,000 daltons. Ascites from three additional cancer patients gave identical results. Physicochemical characterization of the suppressor moiety revealed stability at 70 degrees C for 30 min and at pH 2 and pH 10 for 24 hr. Delipidation by chloroform-methanol extraction, proteolytic enzyme digestion, and protamine sulfate precipitation did not affect activity, suggesting that lipid, simple peptides, and nucleic acids were not crucial. However, periodate oxidation irreversibly destroyed suppressor activity, suggesting the importance of carbohydrate to the molecule and offering one explanation for protease resistance. Similarities in m.w. (50,000 daltons), isoelectric point (pI = 3.4), physical properties (heat and acid stability and resistance to proteases), and immunologic activity of this factor with that released from lymphocytes after in vitro exposure to carcinoembryonic antigen indicates they may be identical. Our results suggest that early aberrant events induced in the immunoregulatory network by tumor-associated antigens may be relevant and may lead to better understanding of immunosuppression in the cancer-bearing host.

A suppressive lymphokine of platelet cytotoxic functions

The in vitro stimulation of mononuclear cells from human peripheral blood with mitogens is known to induce the release of factors (monokines and lymphokines) that possess distinct biologic activities. The present data describe the presence in Con A- and antigen-stimulated T cell supernatants (of man or rat) of a factor able to inhibit, in a dose-dependent manner, the platelet cytotoxicity toward the young larvae of Schistosoma mansoni. The production of oxygen metabolites by IgE-coated platelets, stimulated by anti-IgE or the specific antigen, was, likewise, strongly inhibited by this lymphokine. The producing T lymphocyte subpopulation was identified as OKT 8+. This suppressive lymphokine of platelet functions had an m.w. of 15,000 to 20,000 and a pI of 4.6. It was heat- and acid-stable and sensitive to trypsin and proteinase K, but neuraminidase had no effect on its activity. This platelet suppressive activity was specifically absorbed by platelet membrane, suggesting its action through the binding to a receptor.

Functional and biochemical characterization of a secreted I-J(+) suppressor factor that binds to immunoglobulin

A secreted product of a T cell leukemic cell line, LH-8, was examined for its biochemical and biological properties. The factor that we have termed Immunoglobulin-Binding T cell Suppressor Factor (IgB-TsF) was shown to be suppressive for the in vitro and in vivo humoral response to a variety (but not all) antigens tested. The cell surface phenotype of the LH-8.1 subclone was M.Ig(-), Thy-1(+), L3T4(-), Lyt-2(+), FcR(-), MAC-1(-), and H-2b(+). In addition, both the cell surface and secreted factor, IgB-TsF, of LH-8.1 expressed determinants that were recognized by anti-I-Jb mAbs but not by an anti-I-Jd monoclonal. The same factor also retained an affinity for the Fc portion of approximately 30% of randomly selected, purified mAbs. This binding could be abolished if the Fab or F(ab')2 fragments of these mAb were used, but was found to be unrelated to isotype of the respective mAbs. Using subclones that expressed quantitative differences in their ability to exert suppression as sources of biosynthetically labeled IgB-TsF, we have shown the suppressor activity correlated with a single, 28 kD protein. Furthermore, comparisons of these same subclones that differ in their suppressor activity, do not show any direct correlation of this biological activity with the expression of the previously described T cell receptor genes. It also suggests that at least some suppressor cell subsets may use the same or related family of T cell receptor genes for their recognitive stage of activation as helper and cytotoxic T cell subsets, but not for their effector stage of immunologic suppression.

Tumor-derived suppressor factors (TDSFs) in normal and neoplastic colon and rectum

Acid tumor-derived suppressor factors (TDSFs, isoelectric pH less than 3.0) in extracts of murine fibrosarcomas and human colorectal adenocarcinoma cell lines induce normal murine spleen cells to inhibit delayed-type hypersensitivity (DTH) to the sensitizer dinitrochlorobenzene (DNCB). We sought to determine if TDSF from normal and neoplastic human colon and rectum also inhibited normal human peripheral blood mononuclear cells (PBMC) responses to mitogen and to alloantigens. Collagenase-DNase digests of five freshly isolated carcinomas and paired autologous normal tissues were subjected to preparative isoelectric focusing (pIEF) over a pH range of 2.5 to 9.5. Fractions with isoelectric pH less than 3.0 from three of the five tumors induced normal C3H/HeN spleen cells to inhibit DTH to DNCB. Acid fractions from three tumors and four normal tissues also significantly inhibited the PBMC proliferative response to mitogen and alloantigens. However, the ability of acid fractions to suppress lymphocyte proliferation did not correlate with the induction of suppression of DTH to DNCB. Incubation of human PBMC with acid proliferation inhibitors did not induce suppressor cells that would inhibit the subsequent proliferative response of fresh, autologous PBMC. The acid suppressant from colorectal carcinoma was sensitive to treatment with trypsin but not RNase or DNase, whereas murine TDSF is sensitive to RNase and resistant to treatment with trypsin. The suppressive moiety from one tumor had an apparent mass of 45 kDa by gel filtration chromatography, in contrast to murine TDSF that has a mass of more than 300 kDa. Thus, the acid inhibitor in digests of human colorectal carcinoma is distinct from the TDSF that induces suppressor cells for DTH to DNCB.

Immunosuppressive effects of glycosylation inhibiting factor on the IgE and IgG antibody response

Glycosylation inhibiting factor (GIF) was purified from culture filtrates of a T cell hybridoma, 23A4, by affinity chromatography on anti-lipomodulin Sepharose. The factor exhibited phospholipase inhibitory activity upon dephosphorylation. Immunization of BDF1 mice with aluminum hydroxide gel (alum)-absorbed dinitrophenyl derivatives of ovalbumin (DNP-OA) resulted in persistent IgE and IgG antibody formation. However, repeated injections of the affinity-purified GIF into the DNP-OA-primed mice beginning on the day of priming prevented the primary anti-hapten antibody responses of both the IgE and the IgG1 isotypes. Treatment with GIF also diminished on-going IgE antibody formation in the DNP-OA-primed mice. The treatment changed the nature of IgE-binding factors formed by BDF1 spleen cells. Incubation of spleen cells from OA + alum-primed mice with OA resulted in the formation of IgE-potentiating factor, whereas spleen cells of OA-primed, GIF-treated mice formed IgE-suppressive factor upon antigenic stimulation. It was also found that Lyt-2+ T cells in the OA-primed, GIF-treated mouse spleen cells released GIF, which had affinity for OA and bore I-Jb determinant(s). Transfer of a Lyt-1+ cell-depleted fraction of the OA-primed, GIF-treated mouse spleen cells into naive syngeneic animals resulted in suppression of the primary anti-DNP IgE antibody response of the recipients to alum-absorbed DNP-OA, but failed to affect the anti-DNP antibody response to DNP-keyhole limpet hemocyanin. The results indicate that GIF treatment during the primary response to OA facilitated the generation of antigen-specific suppressor T cells.

Suppression of natural killer cell activity by human seminal plasma in vitro: identification of 19-OH-PGE as the suppressor factor

Human seminal plasma (SP) was found to contain a potent suppressor of human natural killer (NK) cell cytotoxic activity against the K562 erythroleukemia target in vitro. Pooled and filter-sterilized SP reduced the NK cell activity of normal blood donors in a concentration-dependent manner; strong reduction of target cell lysis was observed at a final dilution of 1/400. Possible toxic effects of SP on NK cells were ruled out, because donor leukocytes incubated in a final SP dilution of 1/100 remained greater than 99 percent viable as determined by trypan blue exclusion. SP did not affect the lysability of the tumor targets, but suppressed the cytotoxic activity of the effector leukocytes, an effect that was reversed after washing the leukocytes free of the SP. The suppressive action of SP was retained after heating to 95 degrees C for 10 min, but was removed after adsorption with activated charcoal (Norit-A). Lipids extracted from SP were tested for suppression of NK cell cytotoxic activity, and the active principle was identified with the acidic lipid fraction. Components of the acidic lipid fraction of a single freshly obtained SP sample were separated by high pressure liquid chromatography, and suppression of NK cell cytotoxic activity was found to be associated with the predominant prostaglandins (PG) in this fraction, 19-OH-PGE1 and 19-OH-PGE2. Suppression of cellular immune functions by SP has been described; however, the identity of the suppressor factor (or factors) is unknown. The 19-OH-PGE are present in high concentration in primate semen, and may minimize immunologic sensitization to sperm in females after insemination. In addition, these compounds may suppress NK cell antitumor and antiviral activities in the vagina, as well as in their tissues of origin.

Size and charge heterogeneity of murine IgG-binding factors (IgG-BF)

Size and charge of murine IgG-binding factors (IgG-BF) were determined. Four different sources were used to produce the factors: a) cells of a T cell hybrid (T2D4) constitutively secreting IgG-BF upon incubation in serum-free medium, b) T2D4 cells incubated with mouse monoclonal IgG1 antibody in order to induce in vitro the production of isotype-specific IgG1-BF, c) T2D4 cells induced in vivo by passage as ascites in nude mice and incubated in serum-free medium, and d) in vivo alloantigen-activated T cells (ATC) incubated in serum-free medium. IgG-BF were affinity purified on Sepharose beads coated with rabbit or mouse IgG and identified by their biologic activities, i.e., inhibition of in vitro secondary IgG antibody production to SRBC and inhibition of rosette formation between Fc gamma receptor-positive spleen cells and rabbit IgG-sensitized erythrocytes. IgG-BF produced by either of these cell sources was found to be heterogeneous in both size and charge. In each case, IgG-BF activities were recovered in three fractions of apparent Mr-74,000 to 78,000, 35,000 to 40,000, and 19,000 to 23,000-and in four fractions of pI-4.7 (or 5.3, depending on experimental conditions), 6.5, 7.7, and 8.4. Moreover, IgG-BF translated in vitro from T2D4 poly A RNA by using rabbit reticulocyte lysate exhibited the same heterogeneity. Thus, IgG-BF contain different proteins exerting similar biologic activities.