An artificially designed pore-forming protein with anti-tumor effects

Protein engineering is an emerging area that has expanded our understanding of protein folding and laid the groundwork for the creation of unprecedented structures with unique functions. We previously designed the first native-like pore-forming protein, small globular protein (SGP). We show here that this artificially engineered protein has membrane-disrupting properties and anti-tumor activity in several cancer animal models. We propose and validate a mechanism for the selectivity of SGP toward cell membranes in tumors. SGP is the prototype for a new class of artificial proteins designed for therapeutic applications.     

Catalytic residues and substrate specificity of scytalidoglutamic peptidase, the first member of the eqolisin in family (G1) of peptidases

Scytalidoglutamic peptidase (SGP) is the first-discovered member of the eqolisin family of peptidases with a unique structure and a presumed novel catalytic dyad (E136 and Q53) [Fujinaga et al., PNAS 101 (2004) 3364-3369]. Mutants of SGP, E136A, Q53A, and Q53E lost both the autoprocessing and enzymatic activities of the wild-type enzyme. Coupled with the results from the structural analysis of SGP, Glu136 and Gln53 were identified as the catalytic residues. The substrate specificity of SGP is unique, particularly, in the preference at the P3 (basic amino acid), P1' (small a.a.), and P3' (basic a.a.) positions. Superior substrates and inhibitors have been synthesized for kinetic studies based on the results reported here. kcat, Km, and kcat/Km of SGP for D-Dap(MeNHBz)-GFKFF*ALRK(Dnp)-D-R-D-R were 34.8 s-1, 0.065 microM, and 535 microM-1 s-1, respectively. Ki of Ac-FKF-(3S,4S)-phenylstatinyl-LR-NH2 for SGP was 1.2x10(-10) M. Taken together, we can conclude that SGP has not only structural and catalytic novelties but also a unique subsite structure.     

The Sperm‐surface glycoprotein,SGP, is necessary for fertilization in the frog,Xenopus laevis

To identify a molecule involved in sperm‐egg plasma membrane binding at fertilization, a monoclonal antibody against a sperm‐surface glycoprotein (SGP) was obtained by immunizing mice with a sperm membrane fraction of the frog, Xenopus laevis, followed by screening of the culture supernatants based on their inhibitory activity against fertilization. The fertilization of both jellied and denuded eggs was effectively inhibited by pretreatment of sperm with intact anti‐SGP antibody as well as its Fab fragment, indicating that the antibody recognizes a molecule on the sperm's surface that is necessary for fertilization. On Western blots, the anti‐SGP antibody recognized large molecules, with molecular masses of 65–150 kDa and minor smaller molecules with masses of 20–28 kDa in the sperm membrane vesicles. SGP was distributed over nearly the entire surface of the sperm, probably as an integral membrane protein in close association with microfilaments. More membrane vesicles containing SGP bound to the surface were found in the animal hemisphere compared with the vegetal hemisphere in unfertilized eggs, but the vesicle‐binding was not observed in fertilized eggs. These results indicate that SGP mediates sperm‐egg membrane binding and is responsible for the establishment of fertilization in Xenopus.     

A study of ovarian follicular kinetics, oviduct, fat body, and liver mass cycles in laboratory-maintained Rana cyanophlyctis in comparison with wild-caught frogs.

Ovarian follicular dynamics and fluctuations in fat body, oviducal, and liver masses were studied in captive Rana cyanophlyctis in comparison with wild-caught frogs, sampled at monthly intervals over a period of 12 months. In both the captive and wild-caught frogs first growth phase (FGP) and second growth phase (SGP) or vitellogenic oocytes were produced throughout the period examined; however, changes in ovarian and oviducal weights were less marked in the former group. In the captive frogs SGP oocyte production was reduced by 50%, and, maximum ovarian weight and SGP oocyte number were attained 2-3 months earlier than in wild-caught controls. The FGP oocyte pool in laboratory-maintained frogs, however, was comparable with that of the corresponding wild-caught frogs. Captivity caused a threefold increase in atresia and reduced the number of oocytes reaching SGP. The depletion of fat stores in fat bodies during the later phases of captivity suggests that the deposition of lipids into oocytes (for SGP) was given priority over storage in the fat bodies. The low oviducal weights of captive frogs was correlated with a reduced number of SGP oocytes, which are the source of estrogen. On the other hand, liver weight remained high, indicating adequate hepatic vitellogenin synthesis. Possible reduction in its output was not detected, possibly due to the reduced number of follicles reaching SGP. The findings indicate that stress of captivity decreases gonadotrophins and estrogen levels. Oviducal growth is reduced in captive frogs.(ABSTRACT TRUNCATED AT 250 WORDS)     

唾液酸糖肽的研究进展

唾液酸糖肽(SGP)是一种含有唾液酸寡糖链的N-糖肽,是蛋黄中的主要组成部分。由于其分支型糖链的结构和唾液酸化糖链的存在,SGP及其相关物质有较好的抗细菌和抗病毒作用。以SGP为基础合成SGP的衍生物,有望成为新的预防性抗细菌和抗病毒药物。我们简要综述了SGP的抗菌、抗病毒研究,SGP相关衍生物的合成及其抗菌、抗病毒的机制。     

Inheritance of human-erythrocyte Gerbich blood group antigens.

The blood group-antigenic determinant Gerbich was first described greater than 25 years ago, but its mode of inheritance has not been established. We performed protein immunoblotting by means of anti-beta sialoglycoprotein (SGP) and anti-gamma SGP reagents. The anti-beta SGP was a monoclonal antibody that reacts with normal beta SGP and with the abnormal beta-related SGPs associated with Gerbich and Yus types of Ge-negative red cells. In the families studied, we have shown that the products of the Ge alleles are inherited in an autosomal codominant manner.     

Ebola virus glycoprotein: proteolytic processing, acylation, cell tropism, and detection of neutralizing antibodies

Using the vesicular stomatitis virus (VSV) pseudotype system, we studied the functional properties of the Ebola virus glycoprotein (GP). Amino acid substitutions at the GP cleavage site, which reduce glycoprotein cleavability and viral infectivity in some viruses, did not appreciably change the infectivity of VSV pseudotyped with GP. Likewise, removal of two acylated cysteine residues in the transmembrane region of GP showed no discernible effects on infectivity. Although most filoviruses are believed to target endothelial cells and hepatocytes preferentially, the GP-carrying VSV showed greater affinity for epithelial cells than for either of these cell types, indicating that Ebola virus GP does not necessarily have strong tropism toward endothelial cells and hepatocytes. Finally, when it was used to screen for neutralizing antibodies against Ebola virus GP, the VSV pseudotype system allowed us to detect strain-specific neutralizing activity that was inhibited by secretory GP (SGP). This finding provides evidence of shared neutralizing epitopes on GP and SGP molecules and indicates the potential of SGP to serve as a decoy for neutralizing antibodies.     

A self-glucosylating protein is the primer for rabbit muscle glycogen biosynthesis

In this paper we elucidate part of the mechanism of the early stages of the biosynthesis of glycogen. This macromolecule is constructed by covalent apposition of glucose units to a protein, glycogenin, which remains covalently attached to the mature glycogen molecule. We have now isolated, in a 3500-fold purification, a protein from rabbit muscle that has the same Mr as glycogenin, is immunologically similar, and proves to be a self-glucosylating protein (SGP). When incubated with UDP-[14C]glucose, an average of one molecular proportion of glucose is incorporated into the protein, which we conclude is the same as glycogenin isolated from native glycogen. The native SGP appears to exist as a high-molecular-weight species that contains many identical subunits. Because the glucose that is self-incorporated can be released almost completely from the acceptor by glycogenolytic enzymes, the indication is that it was added to a preformed chain or chains of 1,4-linked alpha-glucose residues. This implies that SGP already carries an existing maltosaccharide chain or chains to which the glucose is added, rather than glucose being added directly to protein. The putative role of SGP in glycogen synthesis is confirmed by the fact that glucosylated SGP acts as a primer for glycogen synthase and branching enzyme to form high-molecular-weight material. SGP itself is completely free from glycogen synthase. The quantity of SGP in muscle is calculated to be about one-half the amount of glycogenin bound in glycogen.     

Study on the packing geometry, stoichiometry, and membrane interaction of three analogs related to a pore-forming small globular protein

A de novo designed pore-forming small globular protein (SGP) with antitumor activity consists of four helices: 3 basic amphipathic helices composed of Leu and Lys surrounding a central hydrophobic helix composed of oligoalanine. These helices are connected by a beta-turn-forming sequence and two beta-turn-unfavorable ones (S. Lee, T. Kiyota, T. Kunitake, E. Matsumoto, S. Yamashita, K. Anzai, and G. Sugihara Biochemistry 1997, Vol. 36, pp. 3782-3791). In the present work, we designed and synthesized three new SGP analogs in order to study the stoichiometric packing geometry and stability of SGP. The replacement of alanines in the central helix of SGP with leucines (SGP-L), which make the helix much larger in size and more hydrophobic, resulted in an equilibrium of monomeric-trimeric structure. The replacement of some Lys residues by Glu residues in the hydrophilic regions of the amphipathic helices (SGP-E) led to a decrease in helical content and the formation of an equilibrium of monomeric-trimeric structure. The alteration of beta-turn regions with Gly residues, which makes these regions flexible (SGP-G), established an equilibrium of monomeric-dimeric states in buffer. The hydrophobic alpha-helix of SGP-L penetrated into the lipid bilayers in a manner that stabilized model membranes and biomembranes, whereas the central helices of SGP-G and -E destabilized them by forming channels. SGP and its analogs may be a useful model to study the role of the hydrophobic and hydrophilic regions in the formation of monomer-oligomer of proteins and to better understand the insertion of membrane targeting proteins into biomembranes.     

Crystal structure of scytalidoglutamic peptidase with its first potent inhibitor provides insights into substrate specificity and catalysis

Scytalidoglutamic peptidase (SGP) from Scytalidium lignicolum is the founding member of the newly discovered\ family of peptidases, G1, so far found exclusively in fungi. The crystal structure of SGP revealed a previously undescribed fold for peptidases and a unique catalytic dyad of residues Gln53 and Glu136. Surprisingly, the beta-sandwich structure of SGP is strikingly similar to members of the carbohydrate-binding concanavalin A-like lectins/glucanases superfamily. By analogy with the active sites of aspartic peptidases, a mechanism employing nucleophillic attack by a water molecule activated by the general base functionality of Glu136 has been proposed. Here, we report the first crystal structures of SGP in complex with two transition state peptide analogs designed to mimic the tetrahedral intermediate of the proteolytic reaction. Of these two analogs, the one containing a central S-hydroxyl group is a potent sub-nanomolar inhibitor of SGP. The inhibitor binds non-covalently to the concave surface of the upper beta-sheet and enables delineation of the S4 to S3' substrate specificity pockets of the enzyme. Structural differences in these pockets account for the unique substrate preferences of SGP among peptidases having an acidic pH optimum. Inhibitor binding is accompanied by a structuring of the region comprising residues Tyr71-Gly80 from being mostly disordered in the apoenzyme and leading to positioning of crucial active site residues for establishing enzyme-inhibitor contacts. In addition, conformational rearrangements are seen in a disulfide bridged surface loop (Cys141-Cys148), which moves inwards, partially closing the open substrate binding cleft of the native enzyme. The non-hydrolysable scissile bond analog of the inhibitor is located in the active site forming close contacts with Gln53 and Glu136. The nucleophilic water molecule is displaced and a unique mode of binding is observed with the S-OH of the inhibitor occupying the oxyanion binding site of the proposed tetrahedral intermediate. Details of the enzyme-inhibitor interactions and mechanistic interpretations are discussed.     

Hematology,plasma biochemistry,and serosurvey for selected infectious agents in southern giant petrels from Patagonia,Argentina

In conjunction with reproductive and feeding ecology studies on southern giant petrels (SGP, Macronectes giganteus) blood samples were collected for baseline health evaluations. Twenty-five adult SGP from a breeding colony in Chubut, Argentina, were sampled during two consecutive breeding seasons, 1999-2000 (n = 15) and 2000-01 (n = 10). Values for hematology, plasma biochemistry, and minerals are described for 20 birds in apparent good physical condition. A serologic survey of exposure to selected infectious agents was also conducted on all 25 birds sampled. Southern giant petrels were serologically negative for evidence of exposure to infectious laryngotracheitis virus, avian encephalomyelitis virus, avian influenza virus, avian reovirus, infectious bursal disease virus, infectious bronchitis virus, paramyxovirus 1, 2, and 3 virus, Chlamydophila, and Aspergillus. Antibodies to avian adenovirus were found in 14% of SGP during the first sampling season, and 60% in the second year. Additionally, all birds were negative for antibodies to Salmonella pullorum at the first sampling date, but 90% had low titers the following breeding season. This study contributes to understanding the health status of South Atlantic seabirds and to establishment of baseline information for SGP. Long-term monitoring of pelagic predator-scavenger seabirds such as SGP should be established for the surveillance of marine ecosystem health.     

Role of SGP2, a suppressor of a gpa1 mutation, in the mating-factor signaling pathway of Saccharomyces cerevisiae.

Loss of function of GPA1, which encodes a guanine-nucleotide-binding protein, arrests the cell at the G1 phase and allows it to mate, suggesting that the gpa1 mutation spontaneously exerts an intracellular signal that mimics the action of mating factor. We have cloned the SGP2 gene, which was first identified as a secondary mutation that allowed a gpa1::HIS3 mutant to grow and to show a non-cell-type-specific sterile phenotype. Disruption of SGP2 confers temperature-sensitive growth and a-specific sterile phenotypes, characteristics similar to those conferred by the dpr1 (ram) mutation, a suppressor of RAS2Val-19. The following observations indicate that SGP2 and DPR1 are in fact identical. (i) The cloned SGP2 complements both the temperature-sensitive growth and the a-specific sterility of the dpr1 mutant and can be integrated into the chromosomal DPR1 locus. (ii) The cloned DPR1, in turn, complements the ability of sgp2 to suppress the lethality of gpa1::HIS3. (iii) The dpr1 mutation suppresses the growth defect of gpa1::HIS3, and the dpr1 gpa1::HIS3 strain shows a non-cell-type-specific sterile phenotype. (iv) sgp2 is closely linked to the dpr1 locus. The DPR1 product has been shown to be responsible for processing and fatty acid acylation of a-factor and RAS proteins at their carboxyl termini. Therefore, the SGP2 (DPR1) product may be involved in membrane localization of an essential component in the mating-factor signaling pathway.     

X-Ray Crystal Structure of Pyrenocine A,a Phytotoxin from Pyrenochaeta terrestris

The milk fat globule membrane (MFGM) enclosing fat droplets in bovine milk was isolated, and its effects on hydrolysis of milk fat by lipases were investigated by using a gum arabic-stabilized milk fat emulsion as substrate. The addition of isolated MFGM to the reaction mixture markedly inhibited hydrolysis by pancreatic and microbial (Rhizopus delemer) lipases. The inhibition was completely lost on tryptic digestion of MFGM, suggesting that the protein moiety of MFGM played a role in the inhibition. Soluble glycoprotein (SGP) which was isolated from delipidated MFGM produced marked inhibitory activity. The inhibition by SGP was dependent on substrate concentration, suggesting that the inhibition was at least partly due to coverage and blockage of the substrate surface by SGP.     

Sialoglycopeptides isolated from bovine aorta.

Intima-media of bovine aorta was digested with pronase, after preliminary extraction of saline (1%)-soluble substances and fat. Crude glycopeptide fraction was then obtained from the resulting complex carbohydrate fraction by fractionation with CPC (cetylpyridinium chloride). Complete separation of sialoglycopeptides was achieved by chromatography on a DEAE-cellulose column at pH 7.2 followed by repeated chromatography on a DEAE-Sephadex A-25 column at pH 5.2. Nine sialoglycopeptides (SGP 1-SGP 9) thus obtained were homogeneous on high-voltage paper electrophoresis at pH 3.5 and pH 5.2. The analytical data showed great heterogeneity of the carbohydrate chains of these preparations, although they consisted of the same monosaccharides (galactose, glucose, mannose, glucosamine, galactosamine, fucose, and sialic acid), except that SGP 1 lacked galactosamine. Heterogeneity was also observed in their peptide chains. It was noticed, however, that the contents of hexose, hexosamine, and aspartic acid of the fractions (SGP 3, SGP 4, and SGP 5) which eluted from the DEAE-Sephadex A-25 column at lower molarity of the eluting salt were higher than those of the fractions (SGP 7, SGP 8, and SGP 9) which eluted at higher molarity, while the contents of sialic acid and hydroxyamino acids were in an opposite relationship. Representative fractions (SGP 7 and SGP 9) of the latter contained many more alkali-sensitive linkages than those (SGP 3 and SGP 5) of the former, indicating the presence of many more O-glycosidic linkages between hydroxyamino acid(s) and sugar(s) in the latter than in the former. The sialoglycopeptides contained significant amounts of sialic acid, ranging from 10% (sgp 1) to 32.4% (SGP 8). The highest contents were in SGP 8 and SGP 9, which contained equimolar amounts of sialic acid and hexosamine. Furthermore, infrared spectra indicated the presence of sulfate groups in most of the sialoglycopeptides.     

Inhibition of DNA synthesis and cell division by a cell surface sialoglycopeptide

We have isolated and purified a cell surface sialoglycopeptide (SGP) from bovine cerebral cortex cells that previously was shown to be a potent inhibitor of cellular protein synthesis. The following studies were carried out to characterize the potential ability of the SGP to inhibit DNA synthesis and to arrest cell division. Treatment of exponentially proliferating Swiss 3T3 cells with the SGP inhibitor resulted in a marked inhibition of thymidine incorporation within 24 h. When the SGP was removed from inhibited cultures, a sharp rise in 3H-thymidine incorporation followed within 3-4 h that peaked well above that measured in exponentially growing cultures, suggesting that the inhibitory action of the SGP was reversible and that a significant proportion of the arrested cells was synchronized in the mitotic cycle. In addition to DNA synthesis, the inhibitory action of the SGP was monitored by direct measurement of cell number. Consistent with the thymidine incorporation data, the SGP completely inhibited 3T3 cell division 20 h after its addition to exponentially growing cultures. Upon reversal there was a delay of 15 h before cell division resumed, when the arrested cells quickly doubled. Most, if not all, of the growth-arrested cells appeared to have been synchronized by the SGP. The SGP inhibited DNA synthesis in a surprisingly wide variety of target cells, and the relative degree of their sensitivity to the inhibitor was remarkably similar. Cells sensitive to the SGP ranged from vertebrate to invertebrate cells, fibroblast and epitheliallike cells, primary cells and established cell cultures, as well as a wide range of transformed cell lines.     

Immunopotentiating effects of the adjuvants SGP and Quil A. I. Antibody responses to T-dependent and T-independent antigens

The present study was undertaken to compare the effects of two adjuvants, SGP (a starch-acrylamide polymer) and Quil A (purified saponin), with that of aluminum hydroxide (Al(OH)3) on murine primary antibody responses to T-independent (TI) and T-dependent (TD) antigens. All three adjuvants augmented the responses to the TD antigens, dinitrophenyl-keyhole limpet hemocyanin (DNP-KLH), and sheep erythrocytes (SRBC). SGP was the most potent adjuvant and increased the primary IgG response to DNP-KLH as much as 90-fold. Quil A and Al(OH)3 had comparable effects on the primary response to DNP-KLH, but Quil A was less effective than Al(OH)3 for augmenting the primary response to SRBC. Quil A and SGP both augmented the primary IgM and IgG responses to trinitrophenyl-lipopolysaccharide (TNP-LPS), TNP-Brucella (TI-1 antigens), and TNP-Ficoll (TI-2 antigens). Al(OH)3, like most commonly used adjuvants, had little or no effect on responses to TI antigens. The kinetics of the response to TNP-Ficoll was altered by SGP, since peak responses were maintained for at least 7 days, while the response to TNP-Ficoll alone peaked on Day 4 and had declined considerably by Day 7. Both SGP and Quil A could augment responses to both optimal and suboptimal doses of antigen. The adjuvant activity of SGP was diminished, but still effective, when smaller amounts of SGP were used with the immunizing antigen, and all three adjuvants were able to augment primary responses when given in separate injections from the antigen. These results demonstrate that SGP is a very effective adjuvant, and show that both Quil A and SGP have a unique ability to increase antibody responses to TI antigens, suggesting that their effects may be mediated at least partially through B cells.     

TRA-1/GLI controls development of somatic gonadal precursors in C. elegans

TRA-1/GLI is best known as a master regulator of sex determination in the nematode C. elegans, but its fly and vertebrate homologs (e.g. Ci, GLI) regulate embryonic patterning and cell proliferation. In this paper, we show that TRA-1/GLI controls development of the two somatic gonadal precursors (SGPs) in both XX and XO animals, in addition to its role in sex determination. Normally, SGPs reside at the poles of the gonadal primordium and divide according to intrinsic gonadal axes. In tra-1-null mutants, however, SGPs assume non-polar positions and the polarity of one SGP is reversed. Consistent with its SGP function, TRA-1 protein is present in SGPs during embryogenesis and early larval development. Previous studies have shown that the ehn-3 gene also affects SGP positions, and we report here that tra-1 and ehn-3 interact genetically. Whereas SGPs in tra-1 and ehn-3 single mutants are largely normal and generate many descendants, those in tra-1; ehn-3 double mutants do not mature or divide. Furthermore, tra-1 is a dominant enhancer of the ehn-3 gonadal defect, which includes the enhancement of a weak sexual transformation in the gonad. We cloned ehn-3, and found that it encodes a C2H2 zinc-finger protein. A rescuing EHN-3::GFP reporter is predominantly nuclear and expressed specifically in SGPs. The EHN-3 protein is therefore likely to regulate gene expression. We propose that TRA-1/GLI and EHN-3 have overlapping roles in regulation of multiple steps of SGP development. We speculate that regulation of SGP development may be an evolutionarily ancient role of TRA-1/GLI in nematode development.     

The strain-generated electrical potential in cartilaginous tissues: a role for piezoelectricity

The strain-generated potential (SGP) is a well-established mechanism in cartilaginous tissues whereby mechanical forces generate electrical potentials. In articular cartilage (AC) and the intervertebral disc (IVD), studies on the SGP have focused on fluid- and ionic-driven effects, namely Donnan, diffusion and streaming potentials. However, recent evidence has indicated a direct coupling between strain and electrical potential. Piezoelectricity is one such mechanism whereby deformation of most biological structures, like collagen, can directly generate an electrical potential. In this review, the SGP in AC and the IVD will be revisited in light of piezoelectricity and mechanotransduction. While the evidence base for physiologically significant piezoelectric responses in tissue is lacking, difficulties in quantifying the physiological response and imperfect measurement techniques may have underestimated the property. Hindering our understanding of the SGP further, numerical models to-date have negated ferroelectric effects in the SGP and have utilised classic Donnan theory that, as evidence argues, may be oversimplified. Moreover, changes in the SGP with degeneration due to an altered extracellular matrix (ECM) indicate that the significance of ionic-driven mechanisms may diminish relative to the piezoelectric response. The SGP, and these mechanisms behind it, are finally discussed in relation to the cell response.     

Immunopotentiation by SGP and Quil A. II. Identification of responding cell populations

The adjuvants SGP (a starch-acrylamide polymer) and Quil A (purified saponin) were shown to markedly augment antibody responses to T-independent (TI) antigens, suggesting that their adjuvant effects may be at least partially mediated through B cells. The ability of both adjuvants to augment primary responses to trinitrophenyl (TNP)-Ficoll (TI-2 antigen) in athymic nude mice further suggested these adjuvants affect B cells. SGP, however, did not induce a response to the T-dependent (TD) antigen dinitrophenyl-keyhole limpet hemocyanin (DNP-KLH) in athymic nude mice, indicating it was unable to replace the requirement for T-helper cells for responses to TD antigens. Responses to TNP-lipopolysaccharide (LPS) were augmented by SGP in CBA/N X Balb/c immune defective (xid) mice. However, SGP was unable to induce a response to TNP-Ficoll in xid mice. The SGP and Quil A augmented responses to TNP-Ficoll were completely inhibited by the mitotic inhibitor, Velban, indicating that SGP and Quil A increased the plaque-forming cell (PFC) response primarily by stimulating cell proliferation, and not by recruitment of antigen-reactive cells. The effects of the adjuvants on secondary responses were investigated using adoptive transfer experiments. SGP and A1(OH)3 both increased the induction of hapten-specific memory B cells in mice primed with DNP-KLH. SGP, Quil A, and A1(OH)3 also increased priming of carrier specific T cells. Priming of memory B cells with DNP-KLH and either A1(OH)3 or SGP was prevented when T cells were depleted with anti-lymphocyte serum (ALS) at the time of antigen priming, indicating that the augmentation of memory B-cell priming by SGP and A1(OH)3 was dependent on the presence of functional T cells. SGP and Quil A were both unable to augment memory cell induction to the TI antigen, TNP-Ficoll, even though both adjuvants markedly augmented primary IgM and IgG responses to this antigen. Based on these results, it is suggested that SGP and Quil A can mediate their adjuvant effects primarily by a direct or indirect effect on B cells although the adjuvants may also affect T cells to some extent.