Genetic studies on a tumor growth-inhibitory factor in serum of normal mice and its relationship to NK activity

It has been shown that normal mouse serum contains a tumor growth-inhibitory factor (GIF). and that strain-dependent levels of GIF correlate with mouse NK activity. To further analyze the genetic control of GIF we have studied the growth-inhibitory activity of normal mouse serum from 8 different mouse strains and their F1 hybrids. A sensitive method using a chromogenic substrate for an endogenous lysosomal enzyme was used to measure the inhibitory activity of normal mouse serum on the mouse B16 melanoma. The highest level of GIF was found in old mice, lower activity in serum of young animals and no activity in suckling mice. To compare the genetic control of GIF and NK, spleen NK activity against B16 as well as YAC-1 targets was measured in parallel in the same animals. Confirming previous results we found the H-2k strains CBA and C3H to have high levels of GIF as well as NK activity, while the strain A/Sn and the A congenic strain A.SW had low levels of both activities. Experiments with H-2d and H-2b strains, however, showed that GIF and NK had a different genetic control; thus the DBA/2 and Balb/c strains had considerably higher GIF activity than the C57B1 and Leaden strains, while the reverse was true for NK activity. In F1 hybrid crosses between strains with high and low activity, high activity was inherited as a dominant trait for both GIF and NK. A backcross analysis in (A X CBA) X A backcross mice, segregating for NK and GIF showed that the two activities did not cosegregate. These studies therefore demonstrate that GIF and NK activity are under different genetic control, and do not support any direct or simple relationship between GIF and NK cells.     

Growth modulation of human tumor cells by a growth-inhibiting activity derived from tumorigenic V79 chinese hamster cells

Summary A growth-inhibiting activity was identified in supernatants of the neoplastic V79 Chinese hamster cell line based on its ability to inhibit the proliferation of the same cell line. The partially purified activity, provisionally termed “growth inhibiting factor” (GIF) activity, inhibited the growth of a wide variety of human tumor cells, but not various normal human fibroblasts. This species-nonspecific activity was reversible, saturable, and highly potent in tumorigenic cell lines, and was noted in both monolayer culture and in soft agar. The inhibitory activity CIF was also exhibited in a chemically defined serum-free medium supplemented with insulin and transferrin. GIF activity was stable to acid, heat, trypsin, and dithiothreitol but sensitive to alpha-chymotrypsin. The pattern of growth modulation by GIF on V79 cells was apparently different from those exhibited by bifunctional peptides such as transforming growth factor-beta, tumor necrosis factor-alpha, and interleukin-1-alpha. In addition, GIF activity cannot be ascribed to these cytokines based on the physicochemical and immunologic properties. Although GIF has yet to be purified to homogeneity, these data suggest that GIF might be a novel growth regulator which has a critical role in regulating growth of V79 cells. The growth modulation of tumor cells by this tumor-derived growth inhibiting activity suggested the presence of an autocrine growth regulatory mechanism even in tumor cells.     

Allelopathy of rice (Oryza sativa L.) root exudates and its relations with Orobanche cumana Wallr. and Orobanche minor Sm. germination

Allelopathy has been considered not only as an environmentally friendly approach for weed control but also a potential reason causing autotoxicity in crop production. In this study, the responses of seeds of lettuce, wheat, rice, clover broomrape (CB), and sunflower broomrape (SB) to the root exudates of rice cultivars were studied. Lettuce germination was promoted by root exudates of Yliangyou 3218 and I-Kung-Pao. Wheat seedling growth was inhibited by all nine rice species. I-Kung-Pao and Ganxin 203 exerted greater autotoxicity than other cultivars. Yongyou 15 and I-Kung-Pao induced the highest germination rate of CB, while Yongyou 13, Zhongzao 22, and I-Kung-Pao induced the highest germination rate of SB. A significantly correlation was noted between germination-inducing ability on broomrape seeds and allelopathic effects on target plants. It is suggested that using broomrape seeds germination is a better receptor for the identification of rice allelopathic potential.     

The Presence of Low Molecular Weight Germinative Substances in Bacillus cereus T Spore Extract

An extract from intact spores of Bacillus cereus T having a germination-inducing activity was studied. Two distinct germinative principles were found through dialysis of the extract. One was diffusible through the dialysis membrane and the other was non-diffusible. The activity of the former fraction was inhibited by the addition of 1 mM glycoletherdiamine-N, N, N', N'-tetraacetic acid (GEDTA), whereas the latter fraction was inactive unless GEDTA was added to the assay system. The diffusible principle maintained the major portion of the activity found in the crude spore extract. By means of high-performance liquid chromatography (HPLC) using a gel permeation chromatography column, 9 fractions were obtained from the deproteinized diffusible fraction. Of those fractions, two fractions (No. 1 and No. 8) were responsible for the germination-inducing activity, but no reconstituted activity was observed unless both fractions No. 1 and No. 8 were added to the assay system. Amino acid analysis of fraction No. 1 revealed that the fraction was rich in free amino acids, especially in alanine. On the other hand, by the use of reverse-phase HPLC and fast atom bombardment mass spectrometry, it was concluded that the effective substance in fraction No. 8 was inosine. Based on these findings, it was suggested that the active substances in fraction No. 1 might be a free amino acid such as L-alanine and/or Ca²⁺ and a Ca²⁺-binding substance.     

Structural and stereospecific requirements for the nucleoside-triggered germination of Bacillus cereus spores

A selection of adenosine analogues was tested for their ability to trigger germination of Bacillus cereus NCIB 8122 spores. The germination-inducing activity was governed by the structural properties of the sugar rather than the base moieties of the nucleosides. Among the sugar-modified analogues, only those containing a 2'-deoxy-D-ribose moiety promoted spore germination. Requirements for a specific molecular structure of the base were not clearly identified, although the highest activity was observed when substituents were inserted at position 6 of the purine ring. All the base-modified analogues, even those such as coformycin and 2'-deoxycoformycin with an expanded base ring, retained the germination-inducing activity of adenosine. However, of the two 2'-deoxycoformycin diastereoisomers characterized by an asymmetric carbon atom at position 8 of the homopurine ring, only the 8S-isomer induced germination, thus indicating that stereospecific configuration of the inducer, at least in the case of 2'-deoxycoformycin, appears to be essential for the initiation of spore germination. The differences in the germination-inducing activity of the various analogues tested were not affected significantly by spore activation at different temperatures, although the higher the activation temperature, the lower was the concentration of each analogue required for maximum germination.     

A monoclonal antibody raised to lipomodulin recognizes T suppressor factors in two independent hapten-specific suppressor networks

Five different Ag-binding suppressor factors from two types of hapten-specific Ts cell hybridomas (TsF1 inducer and TsF3 effector factors) were bound by an anti-lipomodulin mAb (141-B9), that crossreacts with rodent glycosylation inhibition factor (GIF). The Ag-specific suppressor activity in these hybridoma supernatants was bound by anti-lipomodulin columns and could be recovered by elution at acid pH. Additional evidence for the expression of lipomodulin/GIF activity on these TsF molecules was demonstrated by the ability of the eluted fractions to inhibit the glycosylation of IgE-binding peptides during their biosynthesis. The same biologic activity is associated with GIF and lipomodulin. The relationship between TsF and lipomodulin/GIF was confirmed in a serologic assay, which showed that TsF1 and TsF3 molecules, whether purified over Ag, anti-IJ or anti-TsF columns, are recognized by the mAb. 141-B9. The combined results indicate that Ag-binding Ts factors share a common antigenic determinant with phospholipase inhibitory proteins such as lipomodulin and GIF. In addition, the demonstration of glycosylation regulatory activity carried on these TsF molecules suggests a possible mode for their bioactivity.     

G-蛋白 Rab3a 对神经生长抑制因子 (GIF) 抑制神经元细胞生长作用的影响

为了深入研究 Rab3a 和神经生长抑制因子 (GIF) 的相互作用,在大鼠海马神经元细胞原代培养体系中,用 MTT 还原法定量研究了 Rab3a 对 GIF 神经生长活性的影响,发现 Rab3a 可以替代脑提取物而使 GIF 发挥神经生长抑制活性 . 接着又利用多克隆抗体方法研究了 GIF 与 Rab3a 的相互作用,结果说明 Rab3a 是 GIF 发挥神经生长抑制活性所必需的蛋白质,并且它们的相互作用受空间位置的因素影响较大 . 在随后对它们相互作用的机理和可能的生物学意义进行了讨论 .     

Studies on the epitope of neuronal growth inhibitory factor (GIF) with using of the specific antibody

Human neuronal growth inhibitory factor (GIF), a metalloprotein classified as metallothionein-3, is specifically expressed in mammal central nervous system (CNS). In these Studies the specific antibody to human GIF was prepared and used to search the epitope of human GIF by enzyme-linked immunosorbent assay (ELISA) and sequence comparison. The result of ELISA showed the epitope of human GIF may locate on a octapeptide (EAAEAEAE) in the alpha-domain of human GIF, and the result of nerve cell culture indicated that the biological activity of GIF may be affected by the specific antibody.     

The role of Thr5 in human neuron growth inhibitory factor

GIF, a member of the metallothionein (MT) family (assigned as MT3), is a neuron growth inhibitory factor that inhibits neuron outgrowth in Alzheimer’s disease. The conserved Thr5 is one of the main differences between GIF and other members in the MT family. However, natural sheep GIF has an unusual Ala5, casting doubt on the role of common Thr5. We constructed a series of human GIF mutants at site 5, and characterized their biochemical properties by UV spectroscopy, circular dichroism spectroscopy, EDTA reaction, 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB) reaction, and pH titration. Their inhibitory activity toward neuron survival and neurite extension was also examined. Interestingly, the T5A mutant exhibited distinct metal thiolate activity in the EDTA and DTNB reactions, and also lost its bioactivity. Meanwhile, the T5S mutant had similar biochemical properties and biological activity as wild-type human GIF, indicating the hydroxyl group on the Thr5 was critical to the bioactivity of human GIF. We suggest the hydroxyl group in human GIF may help stabilize the biologically active conformation. On the other hand, lack of the hydroxyl group in sheep GIF may be partially compensated by its abnormal structure.Bin Cai and Qi Zheng contributed equally to this work.     

Carrier-specific suppression of antibody responses by antigen-specific glycosylation-inhibiting factors

We previously established an ovalbumin (OA)-specific T cell clone from spleen cells of BDF1 mice, which had been treated by i.v. injections of OA, and constructed antigen-specific T cell hybridomas from the T cell clone. One of the hybridomas constitutively released glycosylation-inhibiting factor (GIF) which lacked affinity for OA, and was called non-specific GIF. Incubation of the same hybridoma cells with OA-pulsed syngeneic macrophages or OA-pulsed B lymphoblastoid cells of BALB/c origin resulted in the formation of GIF molecules that had affinity for OA but not for bovine serum albumin or keyhole limpet hemocyanin. Both the OA-specific GIF and nonspecific GIF bound to monoclonal anti-lipocortin and possessed I-Jb determinants. The OA-specific GIF consisted of two species of molecules, of m.w. 80,000 and 30,000 to 40,000, respectively, whereas the nonspecific GIF from unstimulated cells had an m.w. of 15,000. Intravenous injections of OA-specific GIF or nonspecific GIF into BDF1 mice suppressed both the IgE and IgG1 anti-hapten antibody responses of the animals to dinitrophenyl derivatives of OA (DNP-OA), but OA-specific GIF was much more effective than nonspecific GIF in suppressing the antibody responses. When the same preparations of GIF were injected into DNP-KHL-primed mice, OA-specific GIF and nonspecific GIF were comparable in suppressing the anti-DNP antibody response. In contrast to the 40,000 m.w. species of OA-specific GIF, the 80,000 m.w. OA-specific GIF had carrier-specific suppressive effects. The similarities of antigen-specific GIF to antigen-specific TsF suggest that the phospholipase-inhibiting activity of the molecules may be involved in the immunosuppressive effects of some antigen-specific TsF.     

Important roles of the conserved linker-KKS in human neuronal growth inhibitory factor

Metallothinein-3 (MT3), also named neuronal growth inhibitory factor (GIF), is attractive by its distinct neuronal growth inhibitory activity, which is not shared by other MT isoforms. The polypeptide chain of GIF is folded into two individual domains, which are connected by a highly conserved linker, KKS. In order to figure out the significance of the conserved segment, we constructed several mutants of human GIF (hGIF), including the K31/32A mutant, the K31/32E mutant and the KKS-SP mutant by site-directed mutagenesis. pH titration and DTNB reaction exhibited that all the three mutations made the β-domain lower in stability and looser. More significantly, change of KKS to SP also altered the general backbone conformation and metal–thiolate cluster geometry. Notably, bioassay results showed that the bioactivity of the K31/32A mutant and the K31/32E mutant decreased obviously, while the KKS-SP mutant lost inhibitory activity completely. Based on these results, we proposed that the KKS linker was a crucial factor in modulating the stability and the solvent accessibility of the Cd₃S₉ cluster in the β-domain through domain–domain interactions, thus was indispensable to the biological activity of hGIF.     

Brain Injury and Growth Inhibitory Factor (GIF)—a Minireview

Growth inhibitory factor (GIF) is a small (7 kDa), heat-stable, acidic, hydrophilic metallothionein (MT)-like protein. GIF inhibits the neurotrophic activity in Alzheimer's disease (AD) brain extracts on neonatal rat cortical neurons in culture. GIF has been shown to be drastically reduced and down-regulated in AD brains. In neurodegenerative diseases in humans, GIF expression levels are reduced whereas GFAP expression levels are markedly induced in reactive astrocytes. Both GIF and GIF mRNA are present at high levels in reactive astrocytes following acute experimental brain injury. In chronological observations the level of GIF was found to increase more slowly and remain elevated for longer periods than that of glial fibrillary acidic protein (GFAP). These differential patterns and distribution of GIF and GFAP seem to be important in understanding the mechanism of brain tissue repair. The most important point concerning GIF in AD is not simply the decrease in the level of expression throughout the brain, but the drastic decrease in the level of expression in reactive astrocytes around senile plaques in AD. Although what makes the level of GIF decrease drastically in reactive astrocytes in AD is still unknown, supplements of GIF may be effective for AD, based on a review of current evidence. The processes of tissue repair following acute brain injury are considered to be different from those in AD from the viewpoint of reactive astrocytes.     

生长抑制因子(GIF)与G蛋白Rab3a直接相互作用

生长抑制因子(growth inhibitory factor, GIF), 又称金属硫蛋白-3, 为68个氨基酸组成的脑特异性金属硫蛋白, 具有广泛的生理功能; GIF可能与阿尔茨海默氏症(Alzheimer's)病理相关, 在Alzheimer's脑提取物存在下, 还对神经细胞具有特异的生长抑制活性.然而, 对其发挥生长抑制作用的分子机制并不清楚.运用酵母双杂交系统从人脑cDNA文库中筛选与GIF相互作用因子,从4.1×10⁶个人脑cDNA文库转化子中,首次筛选到Ras家族G蛋白Rab3a C端,包含87个氨基酸的片段能与GIF相互作用;用PCR自人胎盘总cDNA中获得包含完整Rab3a编码序列的cDNA;通过酵母双杂交实验表明,全长Rab3a蛋白亦能与GIF相互作用.免疫共沉淀和蛋白质印迹实验进一步验证了GIF与Rab3a在哺乳动物细胞中可以相互作用; 而且, Rab3a是以GTP结合形式(GTP-Rab3a)与GIF发生相互作用.     

神经生长抑制因子相互作用蛋白的分子克隆、鉴定及其生物学特性

为了探讨神经生长抑制因子(Neuronal growth inhibitory factor,GIF)与Alzheimer’s病(Alzheimer’s disease,AD)的关系,将GIF的cDNA全基因克隆到载体pHyblex中,运用酵母双杂交系统从Alzheimer’s病人脑cDNA文库中筛选出与GIF相互作用蛋白的cDNA克隆。免疫共沉淀和蛋白质印迹实验进一步验证了该蛋白在体内与GIF相互作用的特异性。克隆并鉴定了其中1个与GIF特异性结合的蛋白,与人细胞核dUTP焦磷酸酶(DUT)同源。进一步构建了重组表达质粒pGEX-4T-1／DUT,转化大肠杆菌BL21,经谷胱甘肽-Sepharose 4B亲和层析、凝血酶酶切和Sephacryl S100纯化,得到纯度95％以上的dUTPase蛋白。体外生物学活性检测表明,表达的dUTPase蛋白可以与GIF共同作用嗜铬细胞瘤株(pheochromocytoma)PC12,对细胞的生长产生抑制作用。     

Effects of pH,Ca and Al on the exudation from clover seedlings of compounds that induce the expression of nodulation genes inRhizobium trifolii

The expression of nodulation genes inR. trifolii is induced by flavone compounds present in clover root exudates. In the present experiments a bioassay with an indicator strain ofR. trifolii, which contained thelacZ gene fromEscherichia coli fused to theR. trifolii nodA gene, was used to measure the level ofnod gene expression inR. trifolii. Compounds that stimulatednodA gene expression were shown to be present in exudates of white clover (Trifolium repens L.) and nine cultivars of subterranan clover (T. subterraneum L.) seedling sgrown at a range of pH between pH 3.0 and pH 8.0. Thenod gene-induction activity of exudates was, however, reduced when seedlings of all clover species were grown at pH>7.0 and at pH<4.0 and pH<5.0 for white clover and subterranean clover respectively. No major differences were apparent in the activity of exudates from seedlings of the various cultivars of subterranean clover.Nod gene-induction activity of exudates was shown to increase markedly with seedling age. The presence of Ca at concentrations up to 10 mM in seedling culture solutions also resulted in marked increases in thenod gene-induction activity of seedling exudates. Increases in activity due to the presence of Ca were most apparent at low pH where between 5 and 10-fold increases were observed for white clover and subterranean clover respectively. Conversely, the presence of Al at concentrations up to 60 M in seedling culture solutions had no effect on thenod gene-induction activity of seedling exudates.The observations that both low pH and Ca concentrations affected thenod gene-induction activity of seedling exudates suggested that the net presence of stimulatory flavones in root exudates was an important contributing factor to the acid-sensitive step in nodule formation.     

Production of (+)-5-deoxystrigol by Lotus japonicus root culture

Lotus japonicus roots, cultured in a modified B5 medium, produced and secreted germination stimulants that induced Striga hermonthica seed germination. The germination-inducing activity was detected both in the roots and the culture filtrate. Following bioassay-guided purification procedures, an active compound was isolated from hexane extracts of the roots and the culture filtrate. Based on chromatographic behaviour on HPLC, and 1H NMR, UV, MS and CD spectroscopic analyses, the germination stimulant was identified as (+)-5-deoxystrigol.     

Population dynamic of the extinct European aurochs: genetic evidence of a north-south differentiation pattern and no evidence of post-glacial expansion

Background

Various evolutionary models have been proposed to interpret the fate of paralogous duplicates, which provides substrates on which evolution selection could act. In particular, domestication, as a special selection, has played important role in crop cultivation with divergence of many genes controlling important agronomic traits. Recent studies have indicated that a pair of duplicate genes was often sub-functionalized from their ancestral functions held by the parental genes. We previously demonstrated that the rice cell-wall invertase (CWI) gene GIF1 that plays an important role in the grain-filling process was most likely subjected to domestication selection in the promoter region. Here, we report that GIF1 and another CWI gene OsCIN1 constitute a pair of duplicate genes with differentiated expression and function through independent selection.

Results

Through synteny analysis, we show that GIF1 and another cell-wall invertase gene OsCIN1 were paralogues derived from a segmental duplication originated during genome duplication of grasses. Results based on analyses of population genetics and gene phylogenetic tree of 25 cultivars and 25 wild rice sequences demonstrated that OsCIN1 was also artificially selected during rice domestication with a fixed mutation in the coding region, in contrast to GIF1 that was selected in the promoter region. GIF1 and OsCIN1 have evolved into different expression patterns and probable different kinetics parameters of enzymatic activity with the latter displaying less enzymatic activity. Overexpression of GIF1 and OsCIN1 also resulted in different phenotypes, suggesting that OsCIN1 might regulate other unrecognized biological process.

Conclusion

How gene duplication and divergence contribute to genetic novelty and morphological adaptation has been an interesting issue to geneticists and biologists. Our discovery that the duplicated pair of GIF1 and OsCIN1 has experienced sub-functionalization implies that selection could act independently on each duplicate towards different functional specificity, which provides a vivid example for evolution of genetic novelties in a model crop. Our results also further support the established hypothesis that gene duplication with sub-functionalization could be one solution for genetic adaptive conflict.     

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.     

Modulation of the biologic activities of IgE-binding factors. VII. Biochemical mechanisms by which glycosylation-enhancing factor activates phospholipase in lymphocytes

Cells of the T cell hybridoma 23A4 produce IgE-binding factors lacking N-linked oligosaccharides (unglycosylated form) when they are incubated with IgE alone. In the presence of glycosylation-enhancing factor (GEF) or bradykinin, however, the same cells produce IgE-binding factors with N-linked oligosaccharides (glycosylated form). Switching the cells from the formation of unglycosylated IgE-binding factors to the formation of glycosylated factors was accompanied by the release of both glycosylation-inhibiting factor (GIF) in its phosphorylated form, i.e., phosphorylated lipomodulin, and arachidonate from the cells. Analysis of the biochemical processes for the release of GIF from 23A4 cells showed that affinity-purified GEF or bradykinin induced transient phospholipid methylation and diacylglycerol (DAG) formation, and enhanced 45Ca uptake into the cells. Inhibitors of methyltransferases, i.e., 3-deaza-adenosine plus L-homocysteine thiolactone, inhibited not only phospholipid methylation but also DAG formation and GIF release. Exogenously added 1-oleoyl-2-acetyl glycerol, i.e., a DAG that is permeable to the plasma membrane, induced the release of GIF from the cells. It was also found that 12-O-tetradecanoyl-phorbol 13-acetate (TPA) switched 23A4 cells and normal lymphocytes to the selective formation of N-glycosylated IgE-binding factor, and induced the release of GIF from the cells. 32PO4-labeled lipomodulin was detected in the extract of 23A4 cells 3 to 5 min after the addition of GEF, bradykinin, or TPA. These results indicate that GEF and bradykinin induced the activation of methyltransferases and phospholipase C for the formation of DAG, which in turn activated Ca2+-activated, phospholipid-dependent protein kinase (protein kinase C) for the phosphorylation of lipomodulin. Because lipomodulin loses phospholipase inhibitory activity after phosphorylation, increased phospholipase A2 activity would be expressed by this process.     

IgE-binding factors from mouse T lymphocytes. III. Role of antigen-specific suppressor T cells in the formation of IgE-suppressive factor

BDF1 mice were given three i.v. injections of ovalbumin (OA) to induce antigen-specific suppressor T cells. Incubation of spleen cells of OA-treated mice with homologous antigen resulted in the formation of IgE-suppressive factor. This factor was not derived from antigen-specific suppressor T cells, but suppressor T cells were essential for determining the nature of IgE-binding factors formed. In the spleen cells of OA-treated mice, antigenic stimulation of antigen-primed Lyt-1+ (helper) T cells resulted in the formation of inducers of IgE-binding factor, whereas Lyt-2+, I-J+ T cells released glycosylation-inhibiting factor (GIF), and these two factors, in combination, induced unprimed Lyt-1+ T cells to form IgE-suppressive factor. The role of GIF is to inhibit the assembly of N-linked oligosaccharides on IgE-binding factors during their biosynthesis, and thereby provide them with a biologic activity: suppression of the IgE response. Under the experimental conditions employed, GIF was released spontaneously from antigen-specific suppressor T cells. However, antigenic stimulation of the cells enhanced the release of the factor. GIF from antigen-specific suppressor T cells has a m.w. of 25,000 to 30,000, as estimated by using gel filtration, binds to anti-I-J alloantibodies and to a monoclonal antibody specific for lipomodulin, and has affinity for specific antigen. The possible relationship between antigen-specific GIF and antigen-specific suppressor factors is discussed.