Ia antigenic specificities are oligosaccharide in nature: hapten-inhibition studies

Novel therapeutic approach by culture filtrate of Cryptococcus neoformans var. gattii (CneF) in experimental immune complex glomerulonephritis

The present study was undertaken to determine the therapeutic effect of the culture filtrate of Cryptococcus neoformans var. gattii (CneF) in experimental immune complex glomerulonephritis. Bovine serum albumin (BSA) nephritis was induced in rats by a subcutaneous immunization and daily intravenous administration of BSA. CneF solution at three different doses (36, 54, and 90 mg/kg based on carbohydrate concentration) was administered intraperitoneally at regular 72-h intervals for 4 weeks. Onset of treatment was day 65, and urinary protein was measured at different intervals. Animals were euthanized on day 107. Serum and urine determinants were measured at the time of sacrifice and kidney specimens were examined. Results of this experiment showed that CneF therapy could significantly reduce the urinary protein excretion, blood urea nitrogen (BUN), plasma concentration of triglyceride, and increase the serum HDL cholesterol in treated rats vs. nontreated controls. Moreover, there was significant difference in glomerular changes between treated and nontreated groups. These observations show that the beneficial effect of CneF may be related to decreased number of glomerular leukocytes. Our findings suggest that treatment with CneF as a new antiinflammatory compound can reduce proteinuria, suppress the development of glomerular lesions, and exert lipid-lowering property in a rat model of immune complex glomerulonephritis.

Carbohydrates as recognition molecules in infection and immunity

Consideration of host-parasite interactions encompasses a wide range of phenomena from adhesion to epithelial surfaces to interactions with cells of the immune system. This review focuses on the role of carbohydrates as recognition molecules in these complex interactions. The abundant glycoproteins and glycolipids of cell surfaces of both prokaryotic and eukaryotic cells have the ability to exist in a variety of spatial configurations through alpha- and beta-linkages and the formation of branched structures. This ability carries with it the opportunity of acting as informational molecules greater than that possible for proteins or nucleic acids. The blood group substances are probably the best characterized of these carbohydrate containing molecules. Whilst at present a detailed understanding of the importance of these molecules in host-parasite interaction is lacking, the material covered in this discussion emphasizes the way in which carbohydrate based recognition has been shown to be involved and may provide the basis for further understanding.

Monosaccharide inhibition of cytotoxic T-cell function: demonstration of clone-specific effects

A range of monosaccharides has been tested for their capacity to influence the induction and effector function of alloreactive cytotoxic T (Tc) cells. Strain-specific differences in the capacity of monosaccharides to inhibit Tc cell induction have been demonstrated. Monosaccharides can also inhibit effector function of target cell lysis, but this could only be demonstrated by assessing the effect of sugars added to limiting dilution cultures of alloantigen-stimulated T cells. B10.A(4R) anti-BALB/c Tc cells have been reproducibly inhibited by D-glucosamine and D-galactosamine, as well as D-galacturonic acid, at both the induction and effector phases of the Tc cell response. Analysis of monosaccharide inhibition of cytotoxicity in limiting dilution cultures has confirmed that D-glucosamine is the most effective inhibitor of B10.A(4R) anti-BALB/c Tc cells, while D-galactosamine and D-galacturonic acid inhibit cytotoxicity in only some limiting dilution wells. Analysis of several B10.A(4R) anti-BALB/c Tc cell clones has revealed at least two different 'clone-specific' patterns of inhibition by D-glucose, D-glucuronic acid and D-galacturonic acid. Since Tc cell recognition of antigen is generally specific for class I major histocompatibility complex (MHC) antigens, this data implicates a role for MHC-associated carbohydrate structures expressed by target cells in T-lymphocyte interactions with antigen.

Simple sugars inhibit proliferation of human T lymphocytes in autologous and allogeneic mixed lymphocyte reactions

Several oligo- and monosaccharides were studied for their capacity to modulate lymphocyte proliferation in human allogeneic and autologous mixed lymphocyte reactions (MLR). A defined subset of sugars showed a marked inhibitory effect on lymphocyte proliferative response in the majority of the allogeneic MLR combinations studied. The inhibitory effect disappeared when sugars were added to allogeneic MLR 96 hr after the beginning of culture. These sugars also showed a significant inhibitory power on autologous MLR, performed by using T- and non-T-enriched lymphocytes from the same donor. The reported data suggest that carbohydrate determinants are involved in the proliferative response of human lymphocytes in both autologous and allogeneic MLR.

Inhibitory effects of tunicamycin on the mixed lymphocyte reaction and mitogen-induced lymphocyte blastogenesis

The role of asparagine(Asn)-linked saccharides on the surface of lymphocytes in cellular interactions was examined by performing studies on the effects of tunicamycin (TM), which inhibits the glycosylation of proteins N-glycosylated at asparagine residues, on the mixed lymphocyte reaction (MLR) and mitogen-induced lymphocyte blastogenesis of human lymphocytes by measuring 3H-thymidine (TdR) incorporation. Responses were expressed as percentages of that of the control (MLR without TM). The lymphocyte blastogenesis in the one- and two-way MLR were, respectively, 43.1% and 48.0% of the control at 0.1 microgram/ml of TM, and 5.5% and 7.2% at 1 microgram/ml of TM. The inhibitory effect of TM on the one-way MLR was shown using TM-pretreated stimulator cells, TM-pretreated responder cells or both. TM blocked lymphocyte blastogenesis in the secondary as well as in the primary MLR. The inhibitory effect of TM on the two-way MLR was observed when TM was added on day 0 to day 2, but not on day 4 of incubation. TM blocked mitogen-induced lymphocyte blastogenesis by phytohemagglutinin, concanavalin A or by pokeweed mitogen. As TM had no cytotoxic effect on cultured cells, these inhibitory effects of TM were thought to be due to the loss of Asn-linked saccharides from glycoprotein of the surface of lymphocytes. These findings indicated that Asn-linked saccharides of glycoprotein on the surface of lymphocytes were important in cellular interactions that are necessary for the cellular immune response.

Embryonic and adult forms of two galactosyltransferases differ in their degrees of sialylation

Embryonic and adult chicken liver galactosyltransferases behave differently on DEAE-Sepharose chromatography. After solubilization, two embryonic activities (one transfers galactose in a beta 1-4 linkage to asialo-agalacto-alpha 1-acid glycoprotein and to N-acetylglucosamine; the other transfers galactose in a beta 1-3 linkage to asialo-ovine submaxillary mucin) elute after the bulk of the protein, and after free glucose. The same two enzymes in adults elute more rapidly, almost coincident with the bulk of the protein, and before free glucose. The difference in elution patterns occurs when the column buffer contains 0.1 M NaCl. Without salt, both embryonic and adult transferases bind to the column, but with 0.5 M NaCl, the embryonic and adult transferases elute identically, and with the bulk of the protein. After treatment with neuraminidase, the embryonic transferase activities elute significantly earlier on a DEAE-Sepharose column in the presence of 0.1 M NaCl. The embryonic forms migrate more rapidly than do the adult forms on cellulose acetate electrophoresis, but neuraminidase treatment renders both enzyme forms immobile in this system. Neuraminidase treatment also inhibits the binding of the embryonic transferases to a wheat-germ-agglutinin--Sepharose column. Kinetically, the embryonic and adult transferases are indistinguishable.

Co-purification of galactosyltransferases from chick-embryo liver

Two galactosyltransferases with nearly identical Mr values were purified 5000-7000-fold from microsomal membranes of chick-embryo livers by using several affinity columns. One enzyme transfers galactose from UDP-galactose to form a beta-(1----4)-linkage to GlcNAc (N-acetylglucosamine) or AsAgAGP [asialo-agalacto-(alpha 1-acid glycoprotein)]. The other enzyme forms a beta-(1----3)-linkage to AsOSM [asialo-(ovine submaxillary mucin)]. Both enzymes were solubilized (85%) from a microsomal pellet by using 1% Triton X-100 in 0.1 M-NaCl. The supernatant activities were subjected to DEAE-Sepharose chromatography and four affinity columns: UDP-hexanolamine-Sepharose, alpha-lactalbumin-Sepharose, GlcNAc-Sepharose and either AsAgAGP-Sepharose or AsOSM-Sepharose. The AsAgAGP enzyme [(1----4)-transferase] and the AsOSM enzyme [(1----3)-transferase] behave identically on the DEAE-Sepharose and UDP-hexanolamine-Sepharose columns, and similarly on the alpha-lactalbumin-Sepharose column. Final separation of the two enzymes, however, could only be achieved on affinity columns of their immobilized respective acceptors. Both purified enzymes migrate as a single band on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis after silver staining, and both have an apparent Mr of 68 000. The enzymes were radioiodinated and again subjected to sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Radioautographic analyses showed only one, intensely radioactive, band. Activity stains performed for both transferases after cellulose acetate electrophoresis indicate that, with this system too, both activities have identical mobilities, and co-migrate, as well, with the major, silver-stained, protein band. Kinetic studies with the purified enzymes show that the Km value for GlcNAc, for the (1----4)-transferase, is 4mM; for the (1----3)-transferase the Km value for AsOSM is 5mM, in terms of GalNAc (N-acetylgalactosamine) equivalents. Both enzymes have a Km value of 25 microM for UDP-galactose.

alpha-Fucose inhibits human mixed-lymphocyte culture reactions and subsequent suppressor cell generation

Carbohydrate moieties serve as important sites of interaction for many lymphocyte activities. The potential role of saccharides in the cellular interactions involved in mitogen-, antigen-, and alloantigen-induced proliferation was investigated. Eight different monosaccharides were tested for their inhibitory potential when added to uni- and bidirectional mixed-lymphocyte culture (MLC) reaction as well as to mitogen (Con A, PHA, PWM)-stimulated cultures. Only alpha-L-fucose blocked the MLC reaction in a dose-dependent fashion while having no effect on mitogen stimulation, although antigen-specific stimulation was also blocked by fucose. Similarly alpha-L-fucose specifically inhibited the MLC-induced generation of suppressor cells. Pretreatment of the MLC responder cells with fucose dehydrogenase abolished the MLC reaction while stimulator cell pretreatment had no effect, suggesting that the recognition site of the former contained alpha-L-fucose. The generation and the effector phase of Con A-induced suppressor cells was not affected by fucose, indicating that different receptors are involved in the latter. Apparent competitive inhibition by exogenous fucose of the cell-cell interaction required for the MLC reaction suggested that this monosaccharide is an essential constituent of allogeneic recognition sites.

Reversal of infectious mononucleosis-associated suppressor T cell activity by D-mannose

Epstein-Barr virus-induced infectious mononucleosis (IM) is associated with the activation of suppressor T lymphocytes that profoundly inhibit immunoglobulin (Ig) production in vitro. We have examined the nature of signals operating in the interaction between IM suppressor T cells and their targets, and explored the possibility that a lectin-like receptor molecule and its specific sugar might provide specificity to this interaction. When D-mannose or some of its derivatives, including alpha-methyl-D-mannoside, mannose-6-phosphate, and mannan, were added to suppressed cultures containing IM T lymphocytes and pokeweed mitogen (PWM)-stimulated normal mononuclear cells, a significant enhancement of Ig production was observed. These sugars had little or no effect on Ig production by the PWM-stimulated responder cells alone and thus the enhanced Ig production could be attributed to the reversal of suppression in the co-cultures by these sugars. This was further confirmed by the observation that the sugars were effective only if present during the first 24 h of culture, a time when IM suppressor T cells exert their principal effect. The effect of sugars on Ig production by suppressed cultures was similar to that achieved by decreasing by about fourfold the number of IM T cells in culture. The effect of the sugars is unlikely to represent a form of nonspecific toxicity, since inhibited cultures become responders in the presence of the sugar. Furthermore, toxicity restricted to the suppressor T cells is unlikely, since preincubation of the T cells with the sugars did not reduce their subsequent ability to suppress in secondary indicator cultures. In addition, there was no correlation between the effect of the sugars on T cell proliferation and their effect on T cell-mediated suppression. The reversal of suppression by sugars was dose dependent and demonstrated stereo-specificity in that L-mannose was without effect while D-mannose reversed suppression. These data indicate that D-mannose and some of its derivatives consistently reverse suppression of Ig production by IM T cells and strongly suggest a role for saccharides as critical components in the cellular receptors involved in certain physiologic immune cell interactions.

Sequential change of carbohydrate antigen associated with differentiation of murine leukemia cells: i-I antigenic conversion and shifting of glycolipid synthesis

Cell surface carbohydrate antigens and their metabolism were investigated during the course of differentiation of murine cultured leukemia cells (M1) into macrophage-like cells. The major glycolipids in undifferentiated M1 cells were of the ganglio series, with a small amount of lacto-series glycolipids. A novel branched structure was found as a tetraosylceramide of M1- cells. Upon differentiation, synthesis of lacto-series glycolipids was significantly enhanced and synthesis of globo-series glycolipids was newly induced but the ganglio-series synthesis was much reduced. Undifferentiated cells expressed only i antigen (i+I-Pk-); differentiated macrophage-like cells became I-antigen dominant and Pk-antigen positive (i+/-I+Pk+). The changes proceeded in two sequential steps: (i) an enhancement of lacto-series glycolipid synthesis associated with the conversion of i antigen to I antigen, and (ii) subsequent induction of globo-series glycolipid synthesis accompanied by the appearance of Pk antigen. The experimental system offers a clue for studies on the process of branching (i-to-I conversion) as well as the biological significance of three major glycolipids (globo-, lacto-, and ganglio-series) as markers of cell differentiation.

Monosaccharides define two immunodominant structures of chicken fetal antigen

Chicken fetal antigen (CFA) is an oncodevelopmental antigen associated with hematolymphoid development and differentiation. The immunodominant structures of two CFA determinants were characterized by hapten inhibition of microcytotoxicity (HIM) and were found to be defined by specific monosaccharides. CFA determinants 5 and 11 were effectively (greater than 50%) inhibited by D-mannose and D-glucose, respectively. Therefore, these carbohydrate residues, or closely related structures, are proposed as the immunodominant structures for these antigenic determinants. Implications of these results vis à vis the developmental control and biological role of CFA are discussed.

Selective inhibition by monosaccharides of tumor cell cytotoxicity mediated by mouse macrophages, macrophage-like cell lines, and natural killer cells

A series of monosaccharides were tested for their ability to inhibit the effector phase of macrophage-mediated cytolysis against two susceptible murine tumor target cells, L5178Y and RL male I. Two monosaccharides, D-mannose and N-acetyl-D-galactosamine, were found to decrease cytotoxicity consistently in a dose-dependent manner. However, D-mannose preferentially inhibited lysis of RL male I target cells with little effect on lysis of L5178Y target cells, while the reverse was found with N-acetyl-D-galactosamine. Neither monosaccharide interfered with the activation of macrophages by polyinosinic:polycytidylic acid. Natural killer cell activity was decreased by a 25 mM concentration of D-mannose but not by N-acetyl-D-galactosamine, although increasing concentrations of N-acetyl-D-galactosamine were inhibitory. Neither monosaccharide affected cytotoxicity by alloimmune T cells. Cytotoxicity of macrophage-like cell lines against tumor target cells was also decreased by monosaccharides but the pattern of inhibition was different from that seen with activated macrophage effector cells. Both D-mannose and N-acetyl-D-galactosamine inhibited glucose oxidation by activated macrophages but only D-mannose significantly decreased protein synthesis of activated macrophages. These results indicate that monosaccharides can inhibit macrophage-mediated cytotoxicity in a selective manner with the pattern dependent on the tumor target cell used in the assay.

Characterization of a genetically segregating determinant of chicken fetal antigen by a new hapten inhibition of microcytotoxicity (HIM) assay

The immunodominant structure of a chicken fetal antigen (CFA) determinant was investigated using a new hapten inhibition of microcytotoxicity (HIM) assay. This HIM assay employing avian erythrocytes was shown to be a highly sensitive, economical technique and was verified in a separate experiment using bovine serum albumin (BSA) coupled to Japanese quail peripheral red blood cells (QPRBCs). Inhibition of microcytotoxicity was measured following preincubation of 1 microliter of specific antiserum with 1 microliter of antigen solution. A concentration of 21.1 nM BSA was found to produce effective (50%) inhibition of microcytotoxicity of BSA-coated QPRBCs. The percentage cytotoxicity was determined by estimating the proportion of intact RBCs to free nuclei using an inverted microscope. Staining of the reaction mixtures was not required for scoring. Application of this technique for the characterization of immunodominant structures was demonstrated by the analysis of a CFA determinant known to exhibit both developmental expression and genetic segregation. R-anti-CFA-10 was effectively inhibited only by D-galactose (35.5 mM) and the galactose-containing sugars lactose (28.2 mM), raffinose (29.9 mM), and stachyose (39.8 mM). Implications of the carbohydrate nature of CFA are discussed.

Anti-self receptors. IV. H-2-restricted receptors on thymocytes recognize carbohydrate structures on target cells

Rosetting between thymocytes and autologous erythrocytes in mediated by receptors on thymocytes that primarily recognize self H-2L molecules on erythrocytes. This paper describes preliminary attempts to chemically characterize the receptor and acceptor molecules involved in this H-2-restricted interaction. On the basis of sugar inhibition studies and the sensitivity of the receptors to protease and glycosidase treatments it appears that a protein receptor on thymocytes recognizes the carbohydrate portion of a glycoprotein on erythrocytes. Furthermore, the thymocyte receptor appears to recognize terminal D-galactose, D-mannose and sialic acid residues on a branched-chain carbohydrate structure on erythrocytes, with mouse strains of different H-2 haplotype expressing carbohydrate structures that differ in the linkage of these three terminal sugars. These findings indicate that H-2-restricted carbohydrate-protein interactions can occur between cells, a conclusion with important theoretical implications.

Selective inhibition of T suppressor-cell function by a monosaccharide

Interactions between regulatory T lymphocytes and other cells are assumed to occur at the level of the cell surface. T cells which suppress the generation of specifically effector cells have been described as having antigenic, idiotypic, allotypic and I-region specificity. Other T suppressor cells generated by in vitro cultivation with or without mitogenic stimulation have suppressive activity for T and B cells but no specificity can be assigned to them. These T suppressor cells (Ts) inhibit various lymphoid functions-this either reflects their polyclonal origin or indicates that the structures recognized by the Ts receptors must be common for many cell types. Carbohydrates on cell membrane-inserted glycoproteins or glycolipids might function as specific ligands for recognition by cellular receptors or soluble factors. Almost all cell-surface proteins of mammalian cells are glycosylated. There is evidence for lectin-like carbohydrate binding proteins not only in plants but also in toxins, viruses, prokaryotic cells and even mammalian cells, including T cells. A functional role for these lectin-like proteins has been described for slime moulds and suggested for the selective association of embryonic cells. We report here that addition of a monosaccharide can counteract the effect of T suppressor cells during the generation of alloreactive cytotoxic T cells (CTLs) in vitro.

Spontaneous cytotoxicity by human peripheral blood monocytes: inhibition by monosaccharides and oligosaccharides

The mechanism by which nonimmune cytotoxic effector cells recognize "foreign" targets for cytotoxic attack was investigated utilizing a model system in which cultured human monocytes become cytotoxic to a broad variety of xenogeneic erythrocyte target cells. Such spontaneously cytotoxic human monocytes lyse targets such as chicken (CRBC), horse (HRBC), and rat (RRBC) erythrocytes rapidly and without the addition of exogeneous lectin or antibody. It was found that a variety of simple sugars were capable of blocking the expression of cytotoxicity by precultured human monocytes, and that different oligosaccharides blocked the killing of different targets. For example, cellobiose, a beta 1-4 dimer of D (+) glucose, blocked, CRBC and HRBC lysis in vitro, but had no effect on RRBC lysis. Arabinogalactan (a complex polysaccharide with a galactose beta 1-3 galactose backbone and galactose beta 1-6 galactose side chains with terminal arabinoses), however, blocked HRBC killing, but exhibited only minor inhibition of CRBC killing. Other aspects of cell-mediated function, including lymphocyte transformation to PHA, cell viability as assessed by trypan blue exclusion, monocyte phagocytosis of opsonized CRBC's, and PHA-induced cellular cytotoxicity of CRBC targets, were essentially intact in the presence of identical concentrations of oligosaccharides. Such target-specific inhibition is consistent with the hypothesis that cytotoxic human monocytes recognize various targets through surface receptors which interact with specific monosacchardies, disaccharide, and oligosaccharide sequences present on the target surface.

Demonstration of carbohydrate- and protein determined Ia antigens by monoclonal antibodies

Ten monoclonal alloantibodies were examined by submitting each antibody to five independent tests in order to determine whether they reacted primarily with the glycoprotein or glycolipid class of Ia antigens. The tests employed were as follows: (1) the ability to participate an Ia-like protein from the cell surface as detected by SDS-PAGE; (2) inhibition by protein-Ia extracts free of CHO-Ia; (3) inhibition by CHO-Ia extracts free of protein-Ia; (4) neuraminidase sensitivity of the antigen and (5) inhibition by simple sugars. Using these tests, three of the ten monoclonal antibodies were shown to recognize a CHO-Ia antigen while seven recognized the protein class of Ia antigens. The three CHO-Ia-specific monoclonal antibodies recognized Ia specificities 2, 9 and 17. Monoclonal antibodies recognizing protein-defined Ia.2 and 17 specificities were also characterized. These results imply that some Ia specificities, as defined by genetic testing, can occur both as carbohydrate-defined and protein-defined determinants.--Sugar inhibition studies showed that CHO-Ia.2 has D-glucosamine as its immunodominant sugar while CHO-Ia.17 shows preference for a beta-linked galactose. Furthermore, studies with neuraminidase demonstrated that sialic acid plays a role in the antigenic determinants of CHO-Ia.9 and CHO-Ia.17. Finally, it is noteworthy that CHO-Ia.2, the private specificity of the k haplotype, appears to be expressed only on cells and not in serum. These studies clearly demonstrate the existence of the two Ia antigen classes and emphasize the complexity of the murine I region.

Nature of the antigenic determinants of T locus antigens

The nature of the antigenic specificities of several antigens associated with the T/t complex in the mouse were analyzed by means of glycosidase and haptene inhibition studies. Results indicate that on testicular cells sugar residues are involved in at least six different T/t antigenic determinants. The immunodominant sugar appears to be different for each of the specificities. The specificity for the following T/t antigens resides predominantly in the sugars indicated: T:sialic acid; t12:beta-D-galactose; tw32:beta-D-galactose; t0:L-fucose; tw1:N-acetyl-D-galactosamine; tw18:L-fucose. It seems probable that these sugars are found at the terminal reducing ends of the carbohydrate portion of T/t-bearing moleculse. These studies imply that at least some of the genes in the T locus code for glycosyltransferases or regulators of glycosyltransferases which modigy oligosaccharide structures and impart specificity to the T/t antigens by alteration of their terminal sugar residues.

Ia antigens in serum during different murine infections

There exists in the mouse a family of I-region-controlled (Ia) antigens which carry carbohydrate-defined determinants. These antigens appear in serum as glycolipids and seem to be actively secreted by antigen-activated T-cells. This paper describes the ability of selected viral, bacterial, and protozoal infections of mice to markedly alter the serum levels of these Ia antigens. All the infectious agents examined induced substantial augmentation or suppression of serum Ia concentrations or both. Lymphocytic choriomeningitis (LCM) virus first enhanced and then suppressed serum Ia levels during the course of acute infection. Enhancement occurred during the time of ongoing virus replication and splenic lymphoproliferation while suppression coincided with the peak of the cytotoxic T-cell response and virus clearance. Listeria monocytogenes infection induced a substantial reduction in Ia levels at a time just after marked depletion of T-cells in the spleen. In contrast, Brucella abortus caused a significant increase in Ia levels 7 days postinfection, which correlates with the appearance of peak numbers of bacteria in tissues. Finally, Plasmodium yoelii, a nonlethal malarial parasite which stimulates prolonged T-cell proliferation, augmented serum Ia levels, whereas P. berghei, a lethal parasite which tends to inhibit. T-cell division, suppressed Ia secretion. Possible interpretations of these different results are presented.

Serological analysis of antigen-specific helper factors specific for poly-L(Tyr, Glu)-poly-DLAla--poly-LLys [(T, G)-A--L] and L Glu60-LAla30-LTyr10 (GAT)

In vitro prepared antigen-specific helper factors reactive to the synthetic polypeptide antigens poly-L(Tyr, Glu)-poly-DLAla--poly-LLys [(T, G)-A--L] or LGlu60-LAla30-LTyr10 (GAT) and bearing Ia determinants were analyzed serologically to determine the nature of the Ia determinants they expressed. I subregion-specific mouse anti-Ia antisera were used, and showed that (T, G)-A--L-specific helper factor (HF) contains I-A subregion-controlled determinants, whereas GAT-specific HF carries I-J subregion-controlled antigens. This unexptected finding was confirmed in both the H-2k and H-2 b haplotypes, using a variety of anti-I-J antisera. Rabbit anti-Ia antisera also reacted with both HF which raised the possibility that the Ia determinants on HF may be carbohydrate in nature. The fact that HF has a low molecular weight and yet contains Ia determinants, antigen-binding capacity and idiotypic markers is compatible with this interpretation.

Metabolic carbohydrate-labelling of glycolipids from mouse splenocytes. Mitogen-stimulated B and T cells show different labelling patterns

Splenic lymphocytes from CBA/J, AKR/A/J, BALB/c/A, C57/BL/6J, C3H/HeJ and C3H/Tif nu/nu mice and B lymphocyte or T lymphocyte preparations derived from CBA/J mouse spleen were cultivated in the presence of either concanavalin A, phytohemagglutinin, Salmonella minnesota R595 lipopolysaccharide or Proteus mirabilis soluble lipoprotein. The mitogens stimulated the incorporation of [14C]galactose into acid-insoluble cell material with the same specificity for B or T cells as that known for thymidine incorporation. The glycolipids extracted from mitogen-activated, carbohydrate-labelled B or T cells were compared by thin-layer chromatography and characteristic differences between B and T cells were noted in the ganglioside as well as in the neutral glycolipid fractions. In addition, subsets of B or T cells, namely lipopolysaccharide-responsive or lipoprotein-responsive B-cell populations or nylon-purified T cells may be recognized by characteristic neutral glycolipid bands.

Incorporation of rat histocompatibility (AgB) antigens into liposomes, and their susceptibility to immune lysis

The purification of detergent-solubilized rat histocompatibility antigens is described. The antigen may readily be incorporated into synthetic vesicles (liposomes) which appear to be unilamellar and between 0.1 microbeter and 0.2 micrometer in diameter. The addition of specific antibody leads to the agglutination and precipitation of the liposomes. An enzyme, horseradish peroxidase, may be incorporated into the trapped aqueous phase of the liposome, and its release by antibody and complement can be detected.

Acquisition of murine major histocompatibility complex gene products by schistosomula of Schistosoma mansoni

Schistosoma mansoni schistosomula recovered from the lungs of inbred mice were shown to possess serologically detectable alloantigens on their tegumental surfaces. Using appropriate antisera and infected congenic and recombinant mice as worm donors, gene products of the K and I subregions of the major histocompatibility complex were demonstrated among these alloantigens acquired by the parasites. In contrast, other cell surface alloantigens, such as Thy 1, Ly 1, and H-Y and the serum proteins albumin, C3 and Ig, could not be detected on the surface of lung schistosomula by means of comparable techniques. In another series of experiments, schistosomula recovered from the lungs of mice and reinjected into allogeneic recipients were shown to exchange their alloantigens during an 87-h period of examination. Similarly, lung schistosomula cocultured with allogeneic lymphocytes were shown to acquire major histocompatibility complex (MHC) coded antigens from the cells. It is possible that as acquired host molecules, MHC gene products may disguise the surface of schistosome parasites thereby rendering them insusceptible to immune attack.

Models for the specific adhesion of cells to cells

A theoretical framework is proposed for the analysis of adhesion between cells or of cells to surfaces when the adhesion is mediated by reversible bonds between specific molecules such as antigen and antibody, lectin and carbohydrate, or enzyme and substrate. From a knowledge of the reaction rates for reactants in solution and of their diffusion constants both in solution and on membranes, it is possible to estimate reaction rates for membrane-bound reactants. Two models are developed for predicting the rate of bond formation between cells and are compared with experiments. The force required to separate two cells is shown to be greater than the expected electrical forces between cells, and of the same order of magnitude as the forces required to pull gangliosides and perhaps some integral membrane proteins out of the cell membrane.