Extent of desialation of blood group MM, NN, and MN antigens required for reactivity with human anti-T antibody and Arachis hypogaea lectin

Blood Groups in Infection and Host Susceptibility

Blood group antigens represent polymorphic traits inherited among individuals and populations. At present, there are 34 recognized human blood groups and hundreds of individual blood group antigens and alleles. Differences in blood group antigen expression can increase or decrease host susceptibility to many infections. Blood groups can play a direct role in infection by serving as receptors and/or coreceptors for microorganisms, parasites, and viruses. In addition, many blood group antigens facilitate intracellular uptake, signal transduction, or adhesion through the organization of membrane microdomains. Several blood groups can modify the innate immune response to infection. Several distinct phenotypes associated with increased host resistance to malaria are overrepresented in populations living in areas where malaria is endemic, as a result of evolutionary pressures. Microorganisms can also stimulate antibodies against blood group antigens, including ABO, T, and Kell. Finally, there is a symbiotic relationship between blood group expression and maturation of the gastrointestinal microbiome.

Immunopathology of desialylation: human plasma lipoprotein(a) and circulating anti-carbohydrate antibodies form immune complexes that recognize host cells

Human plasma lipoprotein(a) [Lp(a)], the dominant lipoprotein in atherosclerotic plaques, contains an apo(a) subunit of variable size linked to the apoB subunit of a low-density lipoprotein (LDL) molecule. Circulating lipoprotein immune complexes (ICs) assayed by ELISA using microplate-coated anti-apo(a) or anti-apoB antibody for capture and peroxidase-labelled anti-human immunoglobulins as probe consisted mostly of Lp(a) despite several-fold excess of LDL over Lp(a) in plasma. Microplate coating of plasma lipoprotein IC and probing with antibodies to apo(a) and apoB also revealed negligible presence of LDL compared to Lp(a). Peanut agglutinin specific to desialylated O-glycans bound significantly more to Lp(a) recovered after urea dissociation of IC than to free Lp(a). Plasma lipoproteins separated by ultracentrifugation and desialylated by neuraminidase formed IC with naturally occurring antibodies in normal plasma. These de novo ICs agglutinated desialylated but not normal human RBC in proportion to the polyagglutinin antibody titre of plasma used, suggesting availability of multiple unoccupied binding sites on the participating antibodies even after IC formation. Agglutination was inhibitable by galactosides and decreased 4-8 fold if precursor lipoprotein was selectively depleted of Lp(a), showing agglutinating ICs were contributed mainly by desialylated Lp(a) and galactose-specific antibodies. IC was 2 fold more agglutinating if lipoproteins used contained smaller rather than larger Lp(a) molecules of the same number. Small size/high plasma concentration Lp(a) phenotype and neuraminidase-releasing diseases including diabetes are risk factors for vascular disorders. Results suggest a possible route of Lp(a) attachment to vascular cells that offer terminal galactose on surface glycans following desialylation.

Red blood cell Thomsen-Friedenreich antigen expression and galectin-3 plasma concentrations in Streptococcus pneumoniae-associated hemolytic uremic syndrome and hemolytic anemia

BACKGROUND

Pneumococcal hemolytic uremic syndrome (P-HUS) is a rare but severe complication of invasive pneumococcal disease (IPD) in young children. Consensual biologic diagnosis criteria are currently lacking.

STUDY DESIGN AND METHODS

A prospective study was conducted on 10 children with culture-confirmed IPD. Five presented with full-blown P-HUS, three had an incomplete form with hemolytic anemia and mild or no uremia (P-HA), and two had neither HUS nor HA. Thomsen-Friedenreich (T), Th, and Tk cryptantigens and sialic acid expression were determined on red blood cells (RBCs) with peanut (PNA), Glycine soja (SBA), Bandeiraea simplicifolia II, and Maackia amurensis lectins. Plasma concentrations of the major endogenous T-antigen-binding protein, galectin-3 (Gal-3), were analyzed.

RESULTS

We found that RBCs strongly reacted with PNA and SBA lectins in all P-HUS and P-HA patients. Three P-HUS and three P-HA patients showed also concomitant Tk activation. Direct antiglobulin test (DAT) was positive in three P-HUS (one with anti-C3d and two with anti-IgG) and two P-HA patients (one with anti-C3d and one with anti-IgG). RBCs derived from the two uncomplicated IPD patients reacted with PNA but not with SBA lectin. Gal-3 plasma concentrations were increased in all P-HUS patients.

CONCLUSIONS

The results indicate high levels of neuraminidase activity and desialylation in both P-HUS and P-HA patients. T-antigen activation is more sensitive than DAT for P-HUS diagnosis. Combining PNA and SBA lectins is needed to improve the specificity of T-antigen activation. High concentrations of Gal-3 in P-HUS patients suggest that Gal-3 may contribute to the pathogenesis of P-HUS.

Cancer vaccines and carbohydrate epitopes

Tumor-associated carbohydrate antigens (TACA) result from the aberrant glycosylation that is seen with transformation to a tumor cell. The carbohydrate antigens that have been found to be tumor-associated include the mucin related Tn, Sialyl Tn, and Thomsen-Friedenreich antigens, the blood group Lewis related Lewis(Y), Sialyl Lewis(X) and Sialyl Lewis(A), and Lewis(X) (also known as stage-specific embryonic antigen-1, SSEA-1), the glycosphingolipids Globo H and stage-specific embryonic antigen-3 (SSEA-3), the sialic acid containing glycosphingolipids, the gangliosides GD2, GD3, GM2, fucosyl GM1, and Neu5GcGM3, and polysialic acid. Recent developments have furthered our understanding of the T-independent type II response that is seen in response to carbohydrate antigens. The selection of a vaccine target antigen is based on not only the presence of the antigen in a variety of tumor tissues but also on the role this antigen plays in tumor growth and metastasis. These roles for TACAs are being elucidated. Newly acquired knowledge in understanding the T-independent immune response and in understanding the key roles that carbohydrates play in metastasis are being applied in attempts to develop an effective vaccine response to TACAs. The role of each of the above mentioned carbohydrate antigens in cancer growth and metastasis and vaccine attempts using these antigens will be described.

Inhibition of spontaneous breast cancer metastasis by anti-Thomsen-Friedenreich antigen monoclonal antibody JAA-F11

Thomsen-Friedenreich antigen (TF-Ag) is expressed in many carcinomas, including those of the breast, colon, bladder, and prostate. TF-Ag is important in adhesion and metastasis and as a potential immunotherapy target. We hypothesized that passive transfer of JAA-F11, an anti-TF-Ag monoclonal antibody, may create a survival advantage for patients with TF-Ag-expressing tumors by cytotoxicity, blocking of tumor cell adhesion, and inhibition of metastasis. This was tested using in vitro models of tumor cell growth; cytotoxicity assays; in vitro, ex vivo, and in vivo models of cancer metastasis; and, finally, in vivo effects in mice with metastatic breast cancer. Unlike some anti-TF-Ag antibodies, JAA-F11 did not enhance breast carcinoma cell growth. JAA-F11 did not induce the killing of 4T1 tumor cells through complement-dependent cytotoxicity or apoptotic mechanisms. However, JAA-F11 blocked the stages of metastasis that involve the adhesion of human breast carcinoma cells to human endothelial cells (human umbilical vein endothelial cells and human bone marrow endothelial cells 60) in in vitro static adhesion models, in a perfused ex vivo model, and in murine lung vasculature in an in vivo metastatic deposit formation assay. JAA-F11 significantly extended the median survival time of animals bearing metastatic 4T1 breast tumors and caused a > 50% inhibition of lung metastasis.

Edible mushroom (Agaricus bisporus) lectin modulates human retinal pigment epithelial cell behaviour in vitro

The retinal pigment epithelium (RPE) plays a major role in the development of proliferative vitreoretinopathy (PVR). In particular, RPE cells are implicated in generating the contraction forces seen. The present study was undertaken to investigate whether human RPE binds a lectin from the common edible mushroom, Agaricus bisporus, and to evaluate the effect of any binding on RPE-mediated matrix contraction in an in vitro model of PVR. Fluorescein isothiocyanate (FITC)-labelled Agaricus bisporus lectin (ABL) was used to study binding of lectin to normal retina, PVR scar tissue specimens and cultured human RPE. The effect of a 3-day exposure of ABL on human RPE-mediated contraction was evaluated using 2- and 3D RPE-populated collagen matrices. Effect of ABL on cell adhesion was measured using a collagen type I adhesion assay and determining the relative cellular attachment using absorbance readings. The normal RPE monolayer did not stain with FITC-ABL while PVR scar tissue stained intensely. Staining of in vitro RPE was characteristic but time-dependent. ABL caused a dose-dependent inhibition of RPE-mediated contraction of both 2D (one-way ANOVA, F = 7.94, p < 0.008) and 3D collagen matrices (one-way ANOVA, F = 164.955, p < 0.001). Pre-incubation of ABL with RPE in the 2D model caused a dramatic arrest of contraction (one-way ANOVA, F = 20.1, p < 0.001) that was due to a dose-dependent inhibition of adhesion (one-way ANOVA, F = 15.603, p < 0.001). Recovery of contraction was partially reversible on removal of ABL and was dependent on initial concentration of the lectin. ABL inhibits contraction and adhesion of human RPE cells in vitro without apparent cytotoxicity. It therefore deserves consideration as a potential therapeutic agent in the prevention and treatment of PVR and other non-ocular anomalous wound-healing processes.

Chemoenzymatic synthesis of glycopolypeptides carrying alpha-Neu5Ac-(2-->3)-beta-D-Gal-(1-->3)-alpha-D-GalNAc, beta-D-Gal-(1-->3)-alpha-D-GalNAc, and related compounds and analysis of their specific interactions with lectins

Glycopolypeptide (1) carrying the beta-D-Gal-(1-->3)-alpha-D-GalNAc unit as a kind model of asialo-type mucin was synthesized through three steps: enzymatic synthesis of p-nitrophenyl disaccharide glycoside, reduction of the p-nitrophenyl group, and coupling of the amino group with the carboxyl group of poly(L-glutamic acid)s (PGA). In a similar manner, glycopolypeptides (2-7) carrying beta-D-Gal-(1-->3)-beta-D-GalNAc, beta-D-Gal-(1-->3)-beta-D-GlcNAc, beta-D-Gal-(1-->6)-alpha-D-GalNAc, beta-D-Gal-(1-->6)-beta-D-GalNAc, alpha-D-GalNAc, and beta-D-GalNAc, respectively, were synthesized as analogous polymers of polymer 1. Glycopolypeptides 8 and 9 as a mimic of sialo-type mucin were further prepared from polymers 1 and 2 as the acceptor of CMP-Neu5Ac by alpha2,3-(O)-sialyltransferase, respectively. Interactions of these glycopolypeptides with lectins were investigated with the double-diffusion test and the hemagglutination-inhibition assay and in terms of an optical biosensor based on surface plasmon resonance. Polymers 1 and 2 reacted strongly with peanut (Arachis hypogaea) agglutinin (PNA) and Agaricus bisporus agglutinin (ABA). On the other hand, polymers 8 and 9 through sialylation from polymers 1 and 2 reacted with ABA, but did not with PNA. Other polymers 3-7 did not show any reactivity for both the lectins. These results show that PNA acts precisely in an exo manner on the beta-D-Gal-(1-->3)-D-GalNAc sequence, while ABA acts in an endo manner. Polymers 6 and 7 substituted with GalNAc reacted strongly with soybean (Glycine max) agglutinin and Vicia villosa agglutinin B4, regardless of the configuration of the glycosidic linkage. The interaction of all polymers with Bauhinia purpurea agglutinin was much stronger than that of the corresponding sugars. Polymers 8 and 9 reacted with wheat germ (Triticum vulgaris) agglutinin (WGA), to which Neu5Ac residues are needed for binding, but polymers 1 and 2 did not. These sugar-substituted glycopolypeptides interacted specifically with the corresponding lectins. Furthermore, polymers 4-7 reacted with WGA, but the corresponding sugars did not. It suggests that the N-acetyl group along the PGA backbone has a cluster effect for WGA. The artificial glycopolypeptides were shown to be useful as tools and probes of carbohydrate recognition and modeling in the analysis of glycoprotein-lectin interactions.

Edible mushroom (Agaricus bisporus) lectin, which reversibly inhibits epithelial cell proliferation, blocks nuclear localization sequence-dependent nuclear protein import

The Galbeta1-3GalNAcalpha (TF antigen)-binding lectin (ABL) from the common edible mushroom (Agaricus bisporus) has a potent anti-proliferative effect without any apparent cytotoxicity. This unusual combination of properties prompted investigation of its mechanism of action. In contrast to soluble lectin, agarose-immobilized, and hence noninternalizable ABL had no effect on proliferation of HT29 colon cancer cells. Electron microscopy of HT29 cells incubated with fluorescein- and gold-conjugated ABL showed internalization of the lectin into endocytotic vesicles and multivesicular bodies. Confocal microscopy showed perinuclear accumulation of fluorescein isothiocyanate-conjugated lectin, which also inhibits HT29 cell proliferation, raising the possibility that the lectin might interfere with nuclear pore function. Transport of heat shock protein 70 into the nucleus in response to heat shock was blocked by preincubation of HT29 cells for 6 h with 40 micrograms/ml ABL. In digitonin-permeabilized cells, nuclear uptake of bovine albumin conjugated to a nuclear localization sequence (NLS)-containing peptide was also inhibited by a 15-min preincubation with 40-100 micrograms/ml ABL. In contrast, serum-stimulated nuclear translocation of mitogen-activated protein kinase, which is NLS-independent, was not affected by pretreatment of cells with the lectin. These results suggest that the anti-proliferative effect of ABL is likely to be a consequence of the lectin trafficking to the nuclear periphery, where it blocks NLS-dependent protein uptake into the nucleus.

Quantitative computerized image analysis of Tn and T (Thomsen-Friedenreich) epitopes in prognostication of human breast carcinoma

The precursors of the blood group N and M-immunodominant structures, Tn and T (Thomsen-Friedenreich) epitopes (EPs) occur in approximately 90% of carcinomas (CAs) but are masked in benign-diseased and healthy tissues. We determined quantitatively on 55 primary invasive ductal breast CAs, stages I to IV, the prognostic value of extent of Tn and T EP expression over an observation period exceeding 5 years postoperatively. Classical, established pathological and histological prognostic characteristic indicators associated with survival were subdivided by standard criteria into favorable and unfavorable categories. Tissue sections were reacted with monoclonal anti-Tn and -T antibodies, followed by the streptavidin-biotin-peroxidase-DAB procedure; counterstain was methyl green. Tn and T EPs were then quantitated by computerized image analysis. Of the 55 CAs, 51 clearly expressed Tn and T, and four had traces. Strong Tn EP expression was statistically significantly associated with shortened 5-year disease-free interval, increasing pTNM stages, positive lymph node status, and increasing combined histological grades. T EPs were usually well expressed but showed no significant association with prognostic factors. Our results suggest that quantitative immunohistochemistry-image analysis of Tn EPs of primary breast CAs may add new parameters to prognostication.

Identification of peptide sequences that bind the Thomsen-Friedenreich cancer-associated glycoantigen from bacteriophage peptide display libraries

The goal of this study was to determine if polypeptides that bind specifically to the carcinoma-associated Thomsen-Friedenreich (T) antigen could be isolated from a random peptide bacteriophage display library. T antigen is a carbohydrate antigen that is exposed and immunoreactive on the surfaces of most primary carcinomas and their metastases, while it is masked on normal cells. Tumor-specific surface carbohydrates are often used as markers of cell differentiation and play a role in cell aggregation, which is an important step in the metastatic process. Therefore, peptides that bind and mask T antigen may yield useful carbohydrate-specific probes and provide insight into carbohydrate-mediated tumor-cell aggregation. A 15-amino acid random peptide bacteriophage display library was screened for polypeptides that exhibited high specificity to two glycoproteins which display T antigen on their surfaces. The results suggest that synthetic peptides identified from the bacteriophage display library have high affinities (Kd approximately 1 microM) and specificities for proteins and human tumor cells which present T antigen. Thus, random bacteriophage peptide display libraries may be a rich source of sequences that bind to carbohydrate antigen structures.

Prognostic significance of T antigen expression in patients with gastric carcinoma

BACKGROUND

Thomsen-Freidenreich (T) antigen, the immediate precursor antigen of the human blood MN system, has been detected in malignant cells, but not in most normal cells in which it is cryptic but can be unmasked by desialylation. In this study, we determined the prognostic significance of T antigen in specimens with gastric carcinoma.

METHODS

Expression of T antigen was studied immunohistochemically in 157 gastric carcinoma tissue specimens obtained at surgery from the First Department of Surgery, Osaka City University Medical School between 1983 and 1987.

RESULTS

T antigen expression was detected in 72 of the tumors (45.9%). The staining pattern was inclined to change from a luminal surface type to a cytoplasmic type in accordance with decreasing degree of cell differentiation. The rate of expression of T antigen significantly increased (P < 0.05) with serosal invasion, and was significantly higher (P < 0.01) in patients with hepatic or lymph node metastasis or peritoneal dissemination than in those without such metastasis or dissemination. Furthermore, among patients with Stage III or IV disease, those with T antigen-positive tumors had a significantly poorer prognosis than those with T antigen-negative tumors.

CONCLUSIONS

Our findings suggest that relationships exist between expression of T antigen and depth of invasion, hepatic metastasis, lymph node metastasis, or peritoneal dissemination, and that T antigen may be a good indicator of the prognosis of patients with gastric carcinoma.

Use of lectins as diagnostic and therapeutic tools for cancer

Within the past few years, lectins have become a well-established means for understanding varied aspects of cancer and metastasis. Evidence is now emerging that lectins are dynamic contributors to tumor cell recognition (surface markers), cell adhesion and localization, signal transduction across membranes, mitogenic stimulation, augmentation of host immune defense, cytotoxicity, and apoptosis. To advance understanding of these lectin-dependent processes, attempts are being made to discover new lectins that have one or more of these functions and to develop lectin- (or glycoconjugate-) based tools that could be used to home in on tumor cells. This review will summarize current research on the lectins and recent advances in the development of lectin-based diagnostic and therapeutic tools for cancer. Additionally, the future potential of lectin-based diagnosis and therapy is discussed.

Thomsen-Friedenreich (T)-active glycoproteins, blood group N antigen precursor glycoproteins and N antigen precursor glycoproteins with T activity from ascitic fluids of liver cancer patients

1. Five perchloric acid-soluble fractions (PASFs) obtained from ascitic fluids of three patients with primary hepatocellular carcinoma (HCC), a patient with liver metastatic carcinoma (LUC) from ureteral carcinoma and human normal serum (NS) were subjected to DEAE-cellulose column chromatography to separate seven glycoprotein fractions, respectively. 2. In this chromatography, two HCC-PASFs gave a Thomsen-Friedenreich (T)-active glycoprotein, respectively. 3. Other HCC-PASF gave a T-active glycoprotein, two blood group N antigen precursor glycoproteins and an N antigen precursor glycoprotein with T activity. 4. LUC-PASF gave two T-active glycoproteins and an N antigen precursor glycoprotein with T activity. 5. NS-PASF did not give these serologically active glycoproteins.

Tn epitope (N-acetyl-D-galactosamine alpha-O-serine/threonine) density in primary breast carcinoma: a functional predictor of aggressiveness

This interpretive review attempts to dovetail advanced work by different groups of investigators on blood group and carcinoma (CA) glycoconjugates that have terminal, immunoreactive Tn epitopes (GalNAc alpha-O-Ser/Thr), and on the interaction of those structures with complementary antibodies and lectins. Fenlon et al. (1987) and Leathem and Brooks (1987) found a positive correlation between primary breast CA aggressiveness and its affinity for Helix pomatia (HPA) lectin. This phenomenon was used successfully to accurately predict, in studies on 305 breast CA patients, early or late CA recurrence and patient survival time. The innate specificity of the large HPA combining groove (aside from its avid reactivity with appropriately spaced GalNAc alpha-O-) remains obscure, despite careful investigation for more than a decade (Baker et al., 1983). Leathem and Brooks presumed that HPA recognizes a hitherto "undefined biological marker" that indicates a breast CA's aggressiveness. Our own work has shown that the chemically fully defined Tn epitope, as measured with human polyclonal and murine monoclonal anti-Tn antibodies, occurs in immunoreactive form in approximately 90% of all breast and lung adenoCAs studied. Tn is occluded and non-reactive in healthy and non-CA-diseased tissues. We found that CA-associated Tn is an adhesion molecule in attachment to healthy cells; an increase in its density on breast CA cell membranes parallels greater aggressiveness of breast tumors in both humans and mice (the only species studied). Thus, Tn may be all or a major part of the postulated "as yet undefined biological marker" associated with high breast CA aggressiveness. Besides being helpful in the elucidation of some aspects of breast CA pathogenesis, these findings on primary breast CA have clinical implications in that they should facilitate stratification of breast CA patients for adjuvant treatment.

13C-nuclear magnetic resonance study of glycophorins AM and AN modified with various pyrylium salts

The environment of the N-terminal amino groups of glycophorins AM and AN has been studied using 13C-NMR spectroscopy and pyrylium salts as amino-blocking agents. The extent of amino blocking was monitored by 13C-reductive methylation of the residual free amino groups. The pyrylium ions reacted with the N-terminal amino groups of the two glycophorins at almost identical rates, which is thought to indicate that the overriding steric bulk of the pyrylium salt may determine the rate of the reaction. The difference in the rates of modification of lysine residues of glycophorins AM) and AN by the pyrylium ions did indicate that there may exist an environmental difference around the lysine residues between the two glycophorins. This environmental difference may result from solution aggregation of the glycophorin A molecules or from some differences in the pKa values of the five lysine residues found in glycophorins AM and AN.

Red blood cell T-activation and hemolysis in surgical intensive care patients with severe infections

The exposure of Thomsen-Friedenreich (T) antigens on RBCs, serum neuraminidase, and serum hemoglobin levels were investigated in 53 adult surgical intensive care unit (ICU) patients with septicemia. Unmasked T-antigens were assayed by a hemagglutination test using peanut agglutinin (PNA) (direct anti-T test), and by an indirect anti-T test employing rabbit anti-PNA globulin. RBC T-activation was demonstrated in 17/53 patients (32%); in 2/53 patients (4%) the direct anti-T test was positive, indicating strong T-exposure. No polyagglutination phenomena were observed. Serum neuraminidase was elevated in 12/17 (71%) patients with T-activation and in 7/36 (19%) patients without T-activation. Free serum hemoglobin was elevated in 12/17 (71%) patients with T-activation and in 5/36 (14%) patients without T-activation. Correlations between T-activation and serum neuraminidase and between T-activation and serum hemoglobin were significant (p less than 0.001). Potentially neuraminidase-releasing bacteria were demonstrated in 13/17 (76%) patients with RBC T-exposure. We conclude that neuraminidase-induced RBC T-activation and subsequent hemolysis may be involved in the pathomechanism of hemolytic anemia in patients with severe infections.

Lectinhistochemical demonstration of galactose- and N-acetyl-D-galactosamine residues in cells of the rat anterior pituitary

Lectins are a useful tool for identification of differently glycosylated hypophyseal hormones, prohormones and glycoconjugates without hormone function. Beta-D-galactose and beta-N-acetyl-D-galactosamine (GalNAc) containing glycoconjugates were identified by light microscopy with biotinylated lectins in immunocytochemically localized cells of the anterior pituitary of the rat. Galactose, histochemically detectable by the peanut lectin (PNA), was found at penultimate position of the carbohydrate chain after removal of sialic acid. Galactose containing cells correspond to gonadotrophs and thyrotrophs located mainly in medioanterior regions of the pituitary. The lectins from the soybean (SBA) and horse gram (DBA) both specific for GalNAc residues, are bound to round and also polygonal cells corresponding again to gonadotrophs and thyrotrophs.

Radioiodinated peanut lectin: clinical use as a tumour-imaging agent and potential use in assessing renal-tubular function

Peanut lectin (PNA) has been shown to have a high affinity for Thomsen-Friedenreich (T) antigen, which is associated with the membrane of many solid tumour cells. PNA labelled with 131I was used as a tumour-imaging substance in patients with known metastatic cancer. Serial gamma scintiscans were obtained in 17 patients following a single injection of 131I-labelled PNA. Only in 1 patient was this technique able to reveal a known metastasis at analogue imaging. In the remaining patients, no visible uptake of 131I-PNA could be demonstrated at sites of known metastases. PNA is rapidly excreted through the kidneys and localizes in the renal tubules. As a tumour-imaging agent, 131I-PNA appears to be without value, but its renal-excretory characteristics make it a potentially useful agent for the in vivo assessment of renal-tubular disorders.

The binding of peroxidase-labelled lectins to human breast epithelium. IV--The reactivity of breast carcinomas to peanut, soy bean and Dolichos biflorus agglutinins

The binding of the lectins from peanut, soy bean and Dolichos biflorus (specific for galactose and/or N-acetyl-D-galactosamine), to human breast carcinomas has been investigated. In contrast to the consistent pattern found in normal breast the reactivity of carcinomas to peanut lectin is varied, the most striking differences being prominent binding without desialation in some tumours and virtual lack of reactivity in others. There tends to be a greater degree of binding of soy bean agglutinin to carcinomas than normal although this is not absolute, and the reverse applies to Dolichos biflorus agglutinin. Comparison of the binding of the three lectins has revealed a complex heterogeneity of the carbohydrate chains within individual tumours and between different carcinomas. A significant relationship between peanut lectin binding, with the use of neuraminidase, and tumour differentiation as been found, and to a lesser extent with soy bean agglutinin when desialation is performed. However, the pattern of reactivity of the carcinomas with these three lectins does not appear to be related to local lymph node metastasis.

Tn, a carcinoma-associated antigen, reacts with anti-Tn of normal human sera

Tn antigen is the immediate precursor of the carcinoma (CA)-associated T antigen; both are masked in non-CA tissues. Tn antigen was detected by absorption of human anti-Tn antibody in 46 of 50 primary breast CAs and in all 6 metastases originating from Tn-positive primary CAs. Thirteen of 25 (52%) anaplastic CAs, but only 2 of 15 (13%) well differentiated CAs had more Tn than T; 1 anaplastic CA had neither antigen. Eighteen of 20 benign breast lesions had no Tn; the 2 positive lesions were premalignant. All 19 breast CAs, studied immunohistochemically, reacted strongly with human polyclonal anti-Tn; benign or normal glandular tissues had minimal or no reactivity. Among live cancer cell lines, the most malignant sublines had more Tn than T on their cell surfaces. Preliminary studies with rodent monoclonal anti-Tn and anti-T antibodies gave immunohistochemical reactivity patterns similar to those of the polyclonal antibodies, but the former were less sensitive in absorption tests. Tn is a CA marker that promises to be useful in tumor detection.

T and Tn, general carcinoma autoantigens

Primary and metastatic carcinomas are epithelial in origin and comprise by far the largest group of malignant tumors in humans. In most of these tumors, T and Tn antigens, whose epitopes have been synthesized, are uncovered and immunoreactive. In all other tissues T and Tn antigens are masked and not accessible to the immune system; they are generally precursors in normal complex carbohydrate chains. Thus, carcinomas have antigens recognized as foreign by the patients' immune system. The expression of T and Tn antigens has pathogenic and clinical consequences, and the antigens themselves are powerful histological markers in carcinoma diagnosis and frequently in prognosis. Most patients distinguish their carcinoma from all other cells, as shown by strong autoimmune responses to T antigen. These responses are readily measured by assays, and they allow detection of carcinomas with greater sensitivity and specificity frequently earlier than previously possible. Moreover, the extent of T and Tn expression often correlates with carcinoma differentiation; on a molecular level, clustered T- and Tn-active structures on carcinoma cell surfaces may be involved in invasion.

Incidence of T activation in a hospital population

The incidence of T activation in a hospital population has been studied. T poly-agglutinability likely to cause serological problems was found in only 1:10,000 but minor degrees of T activation occurred in 1:200. In a number of cases, severe infections were accompanied by T activation, but we were unable to establish any primary association between T activation and anaemia. The findings suggested that individuals whose erythrocyte sialic acid levels are slightly lower than normal are those who, when hospital patients, are likely to develop various degrees of T activation.

Immune elimination of aging platelets by autologous monocytes: role of membrane-specific autoantibody

Membrane-bound IgG was found only on old populations of platelets from normal individuals. This IgG could be dissociated from senescent cells by repeatedly heating the cells. Heat-eluted IgG (He-IgG) prepared from senescent red blood cells was capable of binding to either heat-treated old platelets or Vibrio cholerae neuraminidase (VCN)-treated young platelets, suggesting expression of a common age-dependent antigen on the senescent red blood cells and old platelets. We analyzed the role of membrane-bound IgG in the immune elimination of aging platelets by direct phagocytosis of different platelet subpopulations by autologous monocytes in vitro. While removal of He-IgG from old platelets inhibited their phagocytosis, preincubation of either heat-treated old or VCN-treated young platelets promoted phagocytosis of these cells by autologous monocytes. The phagocytosis of senescent cells required intact IgG on these cells. Either removal of Fc fragments from He-IgG or treatment of autologous monocytes with Fc fragments prior to the phagocytosis assay resulted in a marked reduction of phagocytosis (greater than 75%). We conclude that Fc receptors on the monocytes and the presence of membrane-specific IgG are crucial elements for immune elimination of senescent platelets.

Phagocytosis of senescent erythrocytes by autologous monocytes: requirement of membrane-specific autologous IgG for immune elimination of aging red blood cells

The role of membrane-bound IgG present on the membrane of senescent erythrocytes in immune eliminations of aging red cells was investigated. Phagocytosis of populations of red blood cells (RBC) of different ages by autologous monocytes was assessed both by direct phagocytosis and by induction of microsomal heme oxygenase. Removal of IgG from older RBCs inhibited their phagocytosis; in contrast, preincubation of neuraminidase-treated young or in vitro aged RBCs with IgG eluted from old cells led to phagocytosis of RBCs treated by autologous monocytes. It was also found that the Fc portion of membrane-bound IgG is essential for the elimination of senescent cells; less than 15% of old heat-inactivated RBCs coated with F(ab)2 fragment of membrane-bound IgG were phagocytosed. In contrast, more than 50% of old heat-inactivated RBCs coated with heat-eluted IgG were phagocytosed by autologous monocytes. A possible mechanism of elimination of aged cells is discussed.

Mechanisms for the removal of senescent human erythrocytes from circulation: specificity of the membrane-bound immunoglobulin G

Direct antiglobulin (Coombs') tests of erythrocyte (RBC) subpopulations confirmed the presence of membrane-bound immunoglobulin G (IgG) on old (density greater than 1.110) human RBCs but not on the young (density less than 1.110) RBCs. After thermal elution of the bound IgG, this Coombs' reaction was negative, but incubation of thermally eluted IgG (He-IgG) with heat-treated RBCs induced a positive antiglobulin test. A positive direct antiglobulin reaction was also obtained after incubation of heat-treated RBCs with anti-T antibody. Similar results were obtained when young RBCs treated with Vibrio cholerae neuraminidase (VCN) were incubated with anti-T or with IgG eluted by heat from old RBCs. Nevertheless, pre-absorption of heat-eluted IgG with T and/or Tn antigen, did not prevent it from binding to either heat-treated old or VCN-treated young RBCs as assessed by the antiglobulin consumption assay. Pre-treatment of either VCN-treated young or heat-treated old RBCs with anti-T and/or anti-Tn antibodies had no significant effect on the binding of radiolabeled He-IgG (eluted from old RBCs). The results indicate that even though desialylation of the erythrocyte membrane is required for binding of both anti-T-Tn and He-IgG, the specificity and consequently the RBC binding sites for He-IgG and anti-T seem to be different.