Detection of serum anti-ganglioside antibodies by latex agglutination assay in Guillain-Barré syndrome: comparison with ELISA

OBJECTIVE: Rapid detection of serum anti-ganglioside antibodies in Guillain-Barré syndrome (GBS) could facilitate early diagnosis and early initiation of treatment, which might shorten the term of illness and reduce sequelae. We examined serum anti-ganglioside antibodies in patients with GBS using the latex agglutination assay developed by Alaedini and Latov (J Immunoassay 21: 377-386, 2000) with some modifications. MATERIALS AND METHODS: We used 75 sera from GBS patients, which exhibited IgG anti-GM1, GD1b, or GQ1b, or IgM anti-GM2 antibodies on previous enzyme-linked immunosorbent assay (ELISA). Blue latex beads (2.5% solution of 0.3 microm) were coated with 1 mg/ml of GM1, GD1b, GQ1b or GM2. Aliquots (4 microl) of serum and the ganglioside-coated particles were mixed and rocked on a glass slide for 30 to 40 seconds. The reaction was observed under a microscope and compared with the antiganglioside antibody titers determined with ELISA. RESULTS: Agglutination was strong in sera of which the IgM or IgG titers of anti-GM1, GD1b, GQ1b or GM2 antibodies were found to be more than 1:6,400 on ELISA except for 2 samples, but weak or absent in sera with titers of 1:3,200. Agglutination was absent in sera of which the antibody titers were less than 1:3,200 on ELISA. CONCLUSION: We could rapidly detect serum IgM and IgG anti-GM1, GD1b, GQ1b and GM2 antibodies in patients with GBS by means of the latex agglutination assay when sera exhibited high titers of the respective antibodies on ELISA. The sensitivity of our agglutination assay was much lower than that of ELISA.     

Comparison of Immunoblotting and ELISA for Detection of Anti-Ganglioside Antibodies in Children with Guillain-Barre Syndrome

Background: Anti-ganglioside antibody assays are widely used for diagnosis of autoimmune peripheral neuropathies. Objective: This study aimed to determine serum levels of anti-ganglioside antibodies in children with Guillain-Barre syndrome by immunoblotting technique and compare the results with those obtained by ELISA method. Method: In this investigation, 50 children with Guillain-Barre syndrome (GBS) who were admitted from July 2006 to July 2008, to Tabriz Children’s hospital in the northwest of Iran were studied. 30 children admitted for various other reasons than GBS were randomly selected as a control group. The levels of anti-ganglioside antibodies in serum were measured by ELISA and immunoblotting methods using commercial kits. Results: Anti-ganglioside antibodies (IgG) were detected in 16 (32%) GBS patients and in 1 (3.3%) control using ELISA assay. However, by employing immunoblotting technique, antibodies against seven gangliosides were found positive in 28 (56%) GBS patients and none in the control group. The sensitivities of immunoblotting and ELISA methods were 56% and 32% and their specificities were 100% and 97%, respectively (p<0.001). Conclusion: According to the clinical criteria of GBS, the specificity and sensitivity of immunoblotting was better than those of ELISA. It is important to notice that the immunoblotting method is able to measure the seven types of antibodies (GM1, GM2, GM3, GD1a, GD1b, GT1b, and GQ1b) simultaneously and it is an easy, routine method with a lower cost.     

Anti-sulfatide reactivity in patients with celiac disease

Objective: To explore a possible significance of the presence of anti-ganglioside and anti-sulfatide antibodies in sera of adult patients with celiac disease (CD) in different clinical scenario.

Methods: We selected 22 adult patients with newly diagnosed CD and 20 age–sex matched non-CD controls. Patients’ serum was tested – before and after at least 6 months on a gluten-free diet (GFD) – for anti-GM1, GM2, GM3, GD1a, GD1b, GD3, GT1a, GT1b, GQ1b and sulfatide IgM, IgG and IgA auto-antibodies, by means of a dot blot technique and enzyme-linked immunosorbent assay (ELISA).

Results: We found the presence of auto-antibodies in untreated patients. In particular, anti-sulfatide IgG antibodies were present in 8 (36%) patients independently of the presence of neurological symptoms. Anti-sulfatide IgA antibodies were present in 3 (19%) patients. During GFD, anti-sulfatide IgG disappeared in all the patients, whereas IgA were observed in 2 patients. Anti-sulfatide, anti-GM1 and anti-GM2 IgM antibodies were also observed in 2 patients on a GFD. All the other auto-antibodies were absent and no demographic or clinical parameters were associated. Non-CD controls did not present any auto-antibody.

Conclusions: We found anti-sulfatide IgG antibodies in CD patients on a gluten-containing diet. Anti-sulfatide IgA antibodies persisted during GFD together with the occurrence of other IgM auto-antibodies. These data suggest a possible link between gluten and IgG auto-antibodies.     

A longitudinal study of autoantibodies against central nervous system tissue and gangliosides in connective tissue diseases

Our objective was to investigate longitudinally, antibodies against central nervous tissue (anti-CNS) derived from bovine brain and gangliosides GM 1, GD1a, GD1b, and GT1b in 91 patients with connective tissue diseases (systemic lupus erythematosus, n = 38; mixed connective tissue disease, n = 16; primary Sjogren's syndrome, n = 7; progressive systemic sclerosis, n= 13; polymyositis/dermatomyositis, n=4; overlap syndrome, n = 5; undifferentiated connective tissue disease, n = 8). Anti-CNS and anti-ganglioside antibodies, measured by enzyme-linked immunosorbent assay, were found in 73% and 63% of patients, respectively. Anti-CNS positive sera were also reactive in Western blotting in 74% of cases and recognized up to 14 different polypeptides from 29 to 130 kDa. Anti-CNS and anti-ganglioside antibodies reflected only in a limited extent the disease activity. In 27 of 58 patients, anti-CNS antibodies remained positive independently of disease activity and antibody levels did not correlate with the phases of exacerbations. A total of 36 of 60 anti-CNS-positive patients, in contrast to two of 22 anti-CNS-negative patients, had major neuropsychiatric manifestations (P < 0.001). Anti-ganglioside antibodies were not significantly associated with neuropsychiatric manifestations. In conclusion, our longitudinal data suggest that anti-CNS antibodies may be an important marker for the diagnosis of cerebral involvement in connective tissue diseases, but the pathogenic role of these autoantibodies remains to be determined.     

Lipopolysaccharides in the development of the Guillain-Barré syndrome and Miller Fisher syndrome forms of acute inflammatory peripheral neuropathies

Guillain-Barré syndrome (GBS), an acute inflammatory polyneuropathy, is preceded in most cases by an infectious illness, and Campylobacter jejuni, a leading cause of acute gastroenteritis, is the most common antecedent to GBS and its ocular variant, Miller Fisher syndrome (MFS). O (Penner) serotyping is considered to distinguish between C. jejuni strains based on differences in lipopolysaccharide (LPS) structure. Serotypes of C. jejuni uncommon in enteritis, such as serotype O:19 and O:41, have been associated with GBS. Chemical studies on the core oligosaccharide (OS) of C. jejuni LPSs from serotypes including O:1, O:2, O:4, O:10, O:19, O:23, O:36 and O:41 have revealed structures that mimic human gangliosides including GM1, GD1a, GD2, GD3, and GM2. Research has focused on the view that molecular mimicry may be a factor in the pathogenesis of GBS. Serum antibodies against gangliosides, particularly GM1 ganglioside, are present in 30% of GBS patients, and are highly associated with MFS, but are generally absent in enteritis cases uncomplicated by neuropathy. Collective data from human and animal studies with anti-ganglioside antibodies suggest a pathogenic role for the antibodies. Many aspects of the pathogenesis of GBS are unclear, in particular how LPS is presented to T cells or the role of host factors in disease development.     

Lack of autologous neutralizing antibodies in the cerebrospinal fluid of HIV-1 infected individuals.

The cerebrospinal fluids (CSF) and sera from HIV-1-infected individuals at different clinical stages were monitored for neutralizing activity against CSF-derived HIV-1 isolates. None of the CSF samples and only one of seven serum samples could neutralize the autologous CSF isolate. CSF samples collected one to two years later from the same patients also lacked autologous neutralizing antibodies against these isolates. However, some CSF samples were able to neutralize heterologous CSF isolates albeit in low titers. HIV antibody positive control sera could readily neutralize all of the CSF isolates demonstrating that these isolates were not resistant to neutralization per se. IgG antibodies against the HIV-1 envelope protein and, specifically, against the V3 loop of HIV-1 gp120 (MN) were present in some CSF samples, although the samples lacked neutralizing activity. In summary, this study demonstrates a lack of autologous neutralizing antibodies in CSF samples when assayed against CSF-derived HIV-1 isolates.     

Possible role of gangliosides in the interaction of colony-stimulating factor with granulocyte-macrophage progenitor cells

Our previous studies have shown that preincubation of murine bone marrow (BM) cells with cholera toxin (CT) or with its B subunit inhibited their responsiveness to colony-stimulating factor (CSF). Because ganglioside GM1 is a component of the CT receptor, the present study was undertaken to determine whether gangliosides interact with CSF and therefore might play a role in the binding sites for CSF. Preincubation of CSF with increasing concentrations of bovine-brain mixed gangliosides resulted in decreased numbers of colonies of BM-derived granulocyte-macrophage progenitor cells (CFU-C) in soft agar. The inhibitory effect of the gangliosides could be reduced by increasing the concentrations of CSF. Evidence for direct binding of CSF to gangliosides was obtained by affinity chromatography of CSF on gangliosides-sepharose beads. CSF activity was retained on the beads and could be eluted with 6 M guanidine HCl. Four different individual gangliosides (GM1, GM2, GD1a, GT1b) were tested for their inhibitory effect on CSF-induced clonal growth of CFU-C. GM1 was the most effective with a 50% inhibition (I50) of clonal growth at a concentration of 15 microM. while the other three gangliosides had slight inhibitory activity (I50 at a concentration greater than 100 microM). In addition, preincubation of BM cells with rabbit anti-GM1 antibodies before addition of CSF reduced the clonal growth of CFU-C to 45%. These data indicate that GM1 interacts with CSF and suggest that gangliosides may play a role in the interaction of CSF with CFU-C and that the binding site for CSF on the surface of these cells might either consist of or contain this ganglioside.     

Continuing intrathecal immunoactivation despite two years of effective antiretroviral therapy against HIV-1 infection

OBJECTIVE: To study the effect of antiretroviral combination treatment on intrathecal immunoactivation in HIV-1 infection. METHOD: Lumbar punctures were performed at baseline, and after 4 months, 1 and 2 years on 30 neurologically asymptomatic, treatment-naive HIV-1-infected patients started on antiretroviral treatment with three or more drugs. Levels of neopterin, beta2-microglobulin and HIV-1 RNA were measured in cerebrospinal fluid (CSF) and blood. RESULTS: All patients continued the study until the 4-month follow-up, although seven discontinued before the 1-year control, and an additional five discontinued before the control after 2 years. Neopterin, beta2-microglobulin and HIV-1 RNA decreased significantly both in CSF and blood, but although 100% of the patients decreased their CSF concentrations of beta2-microglobulin and HIV-1 RNA to normal levels, only 55% had normal CSF neopterin concentrations after 2 years treatment. CONCLUSIONS: In addition to CSF viral load, antiretroviral combination therapy substantially decreases the intrathecal immunoactivation as reflected by CSF neopterin and beta2-microglobulin in neuroasymptomatic HIV-1-infected patients. However, almost half of the patients still have slightly increased CSF neopterin concentrations after 2 years of effective treatment, which might reflect an ongoing low-grade viral replication in brain tissue.     

Effects of antiretroviral treatment on blood-brain barrier integrity and intrathecal immunoglobulin production in neuroasymptomatic HIV-1-infected patients

OBJECTIVES: To study the effect of antiretroviral combination therapy on blood-brain barrier (BBB) integrity and intrathecal immunoglobulin G (IgG) production. METHODS: Lumbar punctures were performed on 38 neurologically asymptomatic, treatment-naive HIV-1-infected patients prior to and during treatment at intervals of approximately 4 months, 1 year and 2 years. Albumin ratio and IgG index were analysed as markers of BBB integrity and intrathecal IgG synthesis. RESULTS: HIV-1 RNA decreased to < 50 HIV-1 RNA copies/mL in the cerebrospinal fluid (CSF) of all patients and in the plasma of all but one patient. Only 5% of patients had elevated albumin ratio values at baseline, while 56% had an elevated IgG index. There was no significant reduction of the albumin ratio or the IgG index. After 2 years of treatment all patients had normal albumin ratio values, while 41% still had increased IgG index levels. CONCLUSIONS: Up to 2 years after the initiation of treatment, the favourable impact of antiretroviral combination treatment on CSF viral load was not accompanied by a similar reduction of intrathecal IgG production. BBB function, measured as the albumin ratio, was not significantly changed in this cohort of neurologically asymptomatic HIV-1-infected patients.     

Which glycolipids are the autoantigens of cytoplasmatic islet cell antibodies?

It has been suggested that acidic glycolipids may be the target of autoimmune phenomena in type 1 diabetes. The aim of the present study was to provide a better understanding of the nature and the chemical structure of pancreatic glycolipids reacting with antibodies from type 1 diabetic patients. Gangliosides and other acidic glycolipids were extracted from human pancreas in chloroform-methanol-water and separated on fractogel TSK DEAE columns. Separated glycolipids were tested for their ability to block islet cell antibody (ICA) binding on frozen pancreatic sections. Furthermore, pancreatic acidic glycolipids and standard gangliosides and sulphatides were used as the substrate for immunostaining on thin layer chromatography (TLC) plates, using ICA-positive and ICA-negative sera. ICA binding was blocked by pancreatic acidic glycolipids even though the alkali treated lipid extract pointed to the alkali-stable acidic glycolipid character of the molecules involved in the blocking effect. ICA⁺ sera specifically reacted on TLC plates with two pancreatic acidic glycolipids, one migrating with the solvent front and the other with a mobility between GM2 and GM1 standards. None of the ICA-positive sera reacted with standard gangliosides (3-LM1, 3-isoLM1, GM1, GD1a, GD1b, GT1b). In addition, ICA⁺ sera reacted with different standard sulphated glycolipids. In conclusion, our results suggest that not only gangliosides, but also sulphatides, are targets of type 1 diabetes-associated antibodies.     

Differences in cerebrospinal fluid gangliosides between "probable Alzheimer's disease" and normal aging.

The four major brain gangliosides, GM1, GD1a, GD1b, and GT1b, were determined in cerebrospinal fluid (CSF) of 43 patients with "probable Alzheimer's disease (AD)" and 40 healthy controls without psychiatric or neurological disorders. The total concentration of the four gangliosides did not differ significantly between "probable AD" group (116 +/- 58 nmol/L) and controls (92 +/- 31 nmol/L), but the proportion between the gangliosides was changed. In the "probable AD" group compared with the age-matched control group, there was an increase in both the GM1 (22.6 +/- 9.3% vs 12.6 +/- 4.1%; p < 0.0001) and GD1a (32.1 +/- 9.8% vs 23.3 +/- 5.7%; p < 0.0005) proportion, and a decrease in the GD1b (20.0 +/- 6.6% vs 23.8 +/- 6.0%; p < 0.05) and GT1b (25.3 +/- 7.9 vs 40.3 +/- 9.3%; p < 0.0001) proportion. The proportion of GM1 showed a positive correlation with age in the control group (r = 0.45; p < 0.01), but a negative correlation with age in the "probable AD" group (r = -0.37; p < 0.05). Thus, although the increase in proportion GM1 in the "probable AD" group was preferentially found in younger "probable AD" patients, it was not caused by age differences. While the pathogenetic mechanism for these changes in CSF-gangliosides in "probable AD" remains to be established, it may reflect the degeneration of nerve cells and synapses.     

Neuroborreliosis in an HIV-1 Positive Patient

Abstract Simultaneous co-infections of Borrelia burgdorferi sensu lato and HIV-1 are rare events, with only six published cases. A case of acute neuroborreliosis with facial palsy, meningoradiculitis (Bannwarth’s syndrome) in an HIV-1 positive individual is described. Diagnosis was confirmed by Western immunoblot analysis of serum and CSF and by proof of intrathecal production of antibodies against B. garinii. The patient was successfully treated with cefotaxime. In all published HIV+ cases, the course of borreliosis did not differ from that of the HIV negative population and the prognosis in properly treated patients was good.     

Antiganglioside antibodies in patients with neuropsychiatric systemic lupus erythematosus.

Antiganglioside antibodies (AGA) were determined in sera and cerebrospinal fluids (CSF) from 50 systemic lupus erythematosus (SLE) patients, and age-matched normal controls. The SLE patients were subdivided according to the type of clinical manifestation into two groups: neuropsychiatric SLE and active SLE without neuropsychiatric manifestation. The presence of these antibodies showed a significant correlation between IgG AGA in the CSF and IgM AGA in the serum and neuropsychiatric SLE. Fifteen patients had this antibody in the CSF without detectable levels in the serum. No correlation was seen between anticardiolipin antibodies in the serum of CSF and neuropsychiatric SLE. The present work suggests that antibodies against gangliosides may be a marker for neuropsychiatric SLE and that intrathecal antibody production can result in the development of this manifestation.     

Vaccines containing purified GM2 ganglioside elicit GM2 antibodies in melanoma patients

GM2, GD2, and GD3 gangliosides are expressed on the surface of human melanoma cells and represent potential targets for immunological control of melanoma growth by monoclonal antibodies and active immunization. The immunogenicity of GM2 was investigated by analyzing the humoral immune response of melanoma patients to vaccination with cell lines selected for high GM2 expression and with vaccines containing purified GM2. The whole-cell vaccine and vaccines containing purified GM2 and bacillus Calmette-Guérin (BCG) elicited GM2 antibody in a high proportion of patients, particularly in GM2/BCG-vaccinated patients pretreated with cyclophosphamide and given a GM2/BCG booster immunization. Vaccines containing purified GM2 and Salmonella minnesota R595 as the adjuvant were also effective, but only in patients pretreated with cyclophosphamide. GM2 antibodies in vaccinated patients were of the IgM class and were cytotoxic for GM2-positive targets in the presence of human complement.     

Treatment benefit on cerebrospinal fluid HIV-1 levels in the setting of systemic virological suppression and failure

OBJECTIVE: To characterize the effect of partially suppressive combination antiretroviral therapy on cerebrospinal fluid (CSF) human immunodeficiency virus (HIV)-1 RNA levels and CSF inflammation. DESIGN: The study was a cross-sectional analysis of 139 HIV-1-infected subjects without active neurological disease, categorized as having successful therapy (plasma HIV-1 RNA level < or =500 copies/mL), having failure of therapy (plasma HIV-1 RNA level >500 copies/mL), or not receiving therapy. The control group consisted of 48 HIV-negative subjects. CSF and plasma HIV-1 RNA assays had a lower limit of quantification of 2.5 copies/mL. Genotypic resistance testing was performed on a subset of subjects. RESULTS: Of the 47 subjects with successful therapy, CSF HIV-1 RNA levels were <2.5 copies/mL in 34 (72%). Only 1 had an HIV-1 RNA level >500 copies/mL. Although plasma HIV-1 RNA levels were similar in 35 subjects with failed therapy and 57 of those not receiving therapy (P=.84), CSF HIV-1 RNA levels were at least 10-fold lower in subjects with failed therapy (P<.0001). This disproportionate effect of treatment on CSF HIV-1 RNA levels was found across the range of plasma HIV-1 RNA levels and was not explained by differences in levels of drug resistance in plasma or CSF. Therapy reduced CSF inflammation in both treated groups. CONCLUSIONS: In our cohort, antiretroviral therapy had a greater effect on HIV-1 RNA levels in CSF than in plasma and reduced intrathecal inflammation, even in the presence of drug resistance.     

Amyotrophic lateral sclerosis with IgM antibody against gangliosides GM2 and GD2

We report a case of amyotrophic lateral sclerosis (ALS) with IgM antibody against gangliosides GM2 and GD2. A 57-year-old woman presented with slowly progressive muscular weakness of the upper extremities and dysarthria. She fulfilled the clinical and electrophysiological criteria of ALS, and died from sudden suffocation about 3 years after the onset of illness. The patient's serum IgM antibody was shown to recognize the structure shared by GM2 and GD2. Since anti-GM2 antibodies have been implicated in motor neuropathy or motor neuron syndrome, this rare case might contribute to the understanding of the immunological aspects of ALS.     

Association between intrathecal anti-HIV-1 immunoglobulin G synthesis and occurrence of HIV-1 in cerebrospinal fluid

The levels of antibodies to HIV-1 and the occurrence of HIV-1 were determined in the cerebrospinal fluid (CSF) and the blood of 60 people in various stages of HIV-1 infection. Intrathecal synthesis of anti-HIV-1 immunoglobulin (Ig) G was detectable at a low frequency in individuals with normal immunological parameters, and in the majority of patients with various degrees of immunodeficiency. The intrathecal production of antibodies to HIV-1 was strongly associated with the recovery of the virus from CSF. A relationship between high anti-HIV-1 IgG levels and occurrence of HIV-1 was also found in blood. Patients without overt neurological symptoms exhibited intrathecal synthesis of anti-HIV-1 IgG as often as those with such symptoms. These findings suggest that intrathecal synthesis of antibodies to HIV-1 is related to a persistent HIV-1 antigenic stimulation in the central nervous system (CNS). HIV-1 often seems to elicit a humoral immune response in the CNS, without concomitant overt neurological symptoms.     

Antibodies to soluble CD4 in HIV-1-infected individuals

A direct enzyme immunoassay (EIA) using the recombinant soluble form of CD4 (sCD4) produced in rodent cells as antigen was applied to detect antibodies to CD4 in sera from HIV-1- and HIV-2-infected patients. High titers of antibodies to sCD4 were found in sera from 12.6% of the HIV-1-infected persons included in this study, but not in 120 normal human sera. The reactivity of these antibodies with sCD4 was confirmed by a Western blot analysis. A possible anti-idiotypic origin of those antibodies was thought to be unlikely in view of the lack of inhibition of the binding of the biotin-labeled monoclonal antibody (mAb) anti-Leu3a by sCD4 positive sera. Attempts to correlate the evolution of the disease with the presence or absence of antibodies to sCD4 in a panel of well documented HIV-1-seropositive cases did not reveal any clear correlation. Sera from HIV-2-infected people (nine sera analysed), sera from HIV-1-infected chimpanzees (10 sera analysed) and sera from humans immunized with a recombinant vaccinia virus expressing gp160 (10 sera analysed) scored negative for antibodies to sCD4. The possible origin and biological significance of the observed antibodies to sCD4 are discussed.     

Toxoplasma gondii antibody profile in HIV-1-infected and uninfected pregnant women and the impact on congenital toxoplasmosis diagnosis in Rio de Janeiro, Brazil

ObjectiveCompare the anti-T. gondii IgG titer between HIV-1 infected and non HIV-1 infected pregnant women and report three cases of congenital toxoplasmosis resulting from reactivation of infection during pregnancy of HIV-1 infected women.MethodsThis study was conducted among 2,270 pregnant women with chronic Toxoplasma gondii infection (absence of IgM and presence of IgG), including 82 HIV-1 infected and 2,188 non-infected women.ResultsThe average anti-T. gondii IgG titer was 127 for the 2,188 non-HIV-1 infected women, and 227 for the 82 HIV-1-infected women (p = 0,007). These results suggested that higher anti-T. gondii IgG titers in HIV-1-infected pregnant women may not be indicative of an elevated risk for fetal infection. In this study three cases of congenital toxoplasmosis that resulted from infection reactivation during pregnancy of HIV-1-infected women were manifested by fetal death, symptomatic infection, and infant without symptoms, respectively. In two of these women, a ten-fold increase in IgG levels above used cutoff was observed (2,320 UI/mL and 3,613 UI/mL, respectively). In the third pregnant women anti-T. gondii IgG titers during pregnancy did not rise despite the occurrence of congenital toxoplasmosis (204; 198; 172 UI/mL).ConclusionsCongenital toxoplasmosis resulting reactivation of infection during pregnancy in the studied group leads us to believe that it is a public health problem, especially in our population, in which seroprevalence of T. gondii infections is high. These findings also suggest that special attention is necessary during pregnancy, because the serologic diagnosis may not be indicative of toxoplasmosis reactivation.     

Ganglioside inhibition of fibronectin-mediated cell adhesion to collagen.

Fibronectin mediates the adhesion of cells to collagen by first binding to the collagen substrate, followed by attachment of the cells to the fibronectin-collagen complex. Bovine brain gangliosides were found to block fibronectin-mediated cell adhesion to collagen in a concentration-dependent manner. The gangliosides did not block the binding of fibronectin to collagen but did prevent the attachment of the cells to the fibronectin-collagen complex. Of the individual gangliosides tested, GT1 and GD1a were the most effective inhibitors followed by GD1b greater than GM1 greater than GM2; GM3 was not an inhibitor. The inhibition of cell adhesion also was observed with the oligosaccharide portion of the gangliosides, but not with ceramides or with a variety of free sugars or glycosaminoglycans. Mild periodate oxidation of mixed gangliosides or of GD1a modified their sialic acid residues and the oxidized gangliosides were no longer inhibitory; subsequent reduction with NaBH4 did not restore the inhibitory activity of the modified gangliosides. These results suggest that specific gangliosides or related sialic acid-containing glycoconjugates on the cell surface may act as the receptors for fibronectin.