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Biomedical subjects

C Ropars

Publications and source records attributed to C Ropars.

At least 55 records · Page 3Linked to original sources
PubMed1979

Human IgE response to the administration of blood components. II. Repeated gammaglobulin injections.

43 adults from a renal dialysis unit staff have received regularly spaced gamma-globulin administrations for hepatitis B prophylaxis. Several blood samples were collected over a prolonged period of time (160 days). Following gamma-globulin administration, anti-immunoglobulin antibodies of the IgE class were detected in 80% of this population, a fortnight after the first injection using serum absorptions on polymerized gamma-globulins or a specific inverse RAST method. The reactivity pattern of these IgE anti-immunoglobulin antibodies was similar to that observed for the anti-immunoglobulin antibodies with "limited specificity" detected by passive hemagglutination, in that they reacted with only one of the immunoglobulins of the panel used for their detection. A decrease of the overall IgE levels was observed in 62% of the subjects for a prolonged period of time following gamma-globulin administration. This suggests a feedback regulation mechanism for the reagin production in man, as it has already been observed in animals. A high incidence of anti-immunoglobulin antibodies of various classes was observed in this study. However, only a small number (4/43) of adverse reactions appeared following gamma-globulin administration. For some of these subjects, the presence of specific IgE anti-immunoglobulin, detected by the inverse-RAST technique, suggests a possible role of such antibodies in some intolerance reactions to gamma-globulin administration.

Absorption↗
PubMed1978

alpha-N-acetyl-D-galactosaminyl- and alpha-D-galactosyltransferase activities in sera of cis AB blood group individuals.

Thirteen cis AB persons from five families were examined for serum glycosyltransferase activities associated with the biosynthesis of A and B blood group characters. Their transferases were generally homogeneous within one family, except for A2/cis AB genotypes, whose A enzyme level was similar to the A2 normal sera, but they varied from one family to another. These activities differed quantitatively and qualitatively from A, B and AB normal sera. Studies of A transferase showed variations in the pH-dependent curve, the effect of cofactors and the capacity of conversion of O red cells into A-active cells. Moreover, A and B transferases behaved differently with respect to their relative levels than did AB heterozygous normal sera. The results were discussed and it was suggested that a mutation of a single enzyme transferring both galactose and N-acetyl-galactosamine could explain these properties.

ABO Blood-Group System↗
PubMed1978

Effects of proteolytic enzymes and neuraminidase on the I and i erythrocyte antigen sites. Quantitative and thermodynamic studies.

The effects of neuraminidase and proteolytic enzymes on I and i reactivities was studied with I and i adult red cells, using radioimmunological methods. An enhanced reactivity after enzyme treatment is not exclusively due to a membrane charge reduction. The increase in site numbers and association constants bring about the gain of the cold agglutinin fixation. The release of N-acetylneuraminic acid residues gradually increases the I antigen site density of I red cells and the i site density of i red cells. Similar behaviour was observed after proteolytic enzyme treatment with papain, bromelin or ficin. The proteolytic treatment of I erythrocyte reveals underlying i receptors on these cells. Following membrane glycoprotein chain removal, anti-i antibodies are specifically fixed on I erythrocytes. The accessibility to antibodies of the determinants responsible for I and i erythrocyte activities was influenced significantly by steric hindrance factors. While N-acetylneuraminic acid release increased antibody affinities for the antigenic receptor, the removal of glycopeptide chains greatly diminished steric hindrance and brought about higher affinity constants. After enzyme treatment, the antigenic structures become more homogeneous in their reaction with antibodies. The heterogeneity of binding constants observed with antigenic determinants of non-treated erythrocytes is probably due to the wide range of spatial distribution of these receptors within the membrane.

Adult↗
PubMed1976

[Acquired B antigen].

Many cases of acquired B antigens, always observed in group A subjects have been so far reported. Most of them were found in patients with digestive tract disease, essentially colonic cancer. An investigation on 200 patients in a gastroenterology department showed that this B-like antigen was quite frequent (10,6%); it occurred only in A1 individuals and was related to infectious syndrome. Immunological and serological studies of many cases had shown that this B-like antigen differs from that of normal B cells. Groupe A1 cells transfused to patients acquired B activity; on the contrary group A2 and O cells remained unchanged. Likewise, only A1 cell became active when incubated in vitro with C. Tertium A., known to contain a deacetylase. In 1970, we postulated that a deacetylase enzyme could be responsible for this B-like antigen: this enzyme could transform the N-acetylgalactosamine (A specific sugar) into galactosamine, which could cross react with anti-B sera. The relationship between the acquired B antigen and a deacetylase was recently confirmed: A1 acquired B cells, chemically acetylated lost their B reactivity and enhanced their A1 activity. A polyagglutinability, different from that associated with T, Tn, Cad, Hempas has been always found in acquired B cells; nervertheless, because of its weakness, it could sometimes be unnoticed. Besides, it disappeared prior to B reactivity in case of recovery. Like acquired B activity, it decreased in low pH medium of after acetylation of the cells. Nevertheless, this polyagglutinability appears, contrarly to acquired B antigen, in vitro, on all the cells, irrespective of their ABO phenotypes. A deacetylation of N-acetyl-neruaminic acid could explain such a phenomenon.

ABO Blood-Group System↗
PubMed1976

[The biochemical aspects of blood group antigens].

The biochemical aspects of the immunodominant structures of blood groups antigens are mainly restricted to the following: ABH and Lewis in secretory fluids or on the red blood cells; P system (P1, P, Pk antigens); MN antigens and related; Tn and Tn antigens; Some hypothesis may be put forward for the I, i antigens. Many other antigens seem to be on the dependence of interactions between proteins and lipids of the red cell membrane; such immunodominant structures are not yet known. Except for the ABH and Lewis groups, the biosynthesis pathways are at present unclear.

ABO Blood-Group System↗
PubMed1976

Groups of alpha-D- galactosyltransferase activity in sera of individuals with normal B phenotype. II. Relationship between transferase activity and red cell agglutinability.

In the Paris population of blood donors with normal B phenotype, two groups can be formed owing to their respective serum alpha-D-galactosyltransferase activity and red cell agglutinability with an anti-B antibody. Both parameters are closely correlated. The agglutinability groups partially overlap. In an African population from various ethnical origins, this correlation was observed only in some individuals. 11 among 20 subjects belonged to a third group defined by a high transferase activity. The third group with the strongest agglutinability previously described by GIBBS et al. [6] were not encountered. On the other hand, serum transferase activity varied inversely as agglutination scores with anti-H (Ulex). Both parameters are closely correlated but not in the same way in Caucasian as in African individuals. In the latter, this relation does not depend on the agglutinability group. The H antigen strength variability, according to ethnical origins, may explain these results.

ABO Blood-Group System↗
PubMed1976

Detection of A1A2 and A2AAm1 heterozygotes among human A blood group phenotypes.

From the variations of alpha-N-acetylgalactosaminyltransferases activities with the pH, evidence was obtained for the recognition of A1A2 heterozygotes in normal A blood group sera. Besides, unusual transferase properties associated with two A2 sera from individuals out of AAm1 siblings, lead to the identification of the very infrequent A2AAm1 genotypes. These results strongly support the simultaneous coexistence of both A1 and A2 transferases in heterozygotes' sera, and bring some new information on the genetical background of the Am phenotype. The meaning of transferase properties directly determined on whole sera is briefly discussed.

ABO Blood-Group System↗
PubMed1976

Passive immunotherapy in HBs Ag fulminant hepatitis. Results on antigenaemia and survival.

19 patients with HBs Ag-positive fulminant hepatitis underwent exchange transfusions and anti-HBs-rich plasma infusions. Circulating HBs Ag disappeared in 17 cases. Circulating anti-HBs detected by RIA was higher in cases with liver regeneration. There was no correlation between circulating anti-HBs level and the amount of anti-HBs-rich plasma administered. Recovery was observed in 36% of the cases and liver regeneration in 47%. As the beneficial effect of such a treatment is not yet evident, a controlled trial should require pairing of patients with respect to the number of exchange transfusions and amount of real or placebo anti-HBs.

Adolescent↗
PubMed1976

Quantitative and thermodynamic measurements on I and i antigens of human red blood cells.

Different homogeneous IgM cold agglutinins (two anti-I, two anti-i and one anti-Il cross-reacting antibodies) have been used to determine the antigen site densities of adult I and i erythrocytes and of cord red cells. The equilibirium constants and the thermodynamic constants of these reactions have been determined. The two anti-I antibodies, which did not combine with i or cord red blood cells, recognized two different determinants on I red cells. The antigen density of the I Fla. receptor was 120,000 sites per erythrocyte and the standard enthalpy change (-deltaH degrees) of the reaction was 18 to 25 kcal/mole. The antigen density of the I Loi. determinant varied according to the red cells tested and the enthalpy change (-deltaH degrees) of these reactions was 50-65 kcal/mole. The i and cord erythrocytes reactive structures were more heterogeneous than those present on I erythrocytes. The equilibrium constants rapidly decreased as the temperature rose and the standard enthalpy changes (-deltaH degrees) ranged from 50 to 90 kcal/mole. Two types of i determinants were observed; one of the anti-i antibodies reacted mainly with an i component present on cord erythrocytes, the other antibody reacted with a different i component present on i adult red-cells. The determinants, recognized by the cross -reacting antibody on I red cells, differed fromthose on i or cord red cells in equilibrium constant, thermodynamic constants, index of heterogeneity of the reaction and in their sensitivity to formalin treatment.

Adult↗
PubMed1975

Assay of alpha-N-acetylgalactosaminyltransferases in human sera. Further evidence for several types of Am individuals.

The study of the alpha-N-acetylgalactosaminyltransferase in the sera of 19 individuals belonging to the rare Am blood group makes it possible to confirm the heterogeneity of this phenotype established on genetical and immunological criteria. Two groups of subjects, Am and Ay, can be distinguished. For the individuals of the first group, named Am, 15 samples (7 families) have been studied, the phenotype is inherited as an allele at the ABO locus. 14 of these subjects, have an alpha-N-acetylgalactosaminyltransferase whose kinetic properties were similar to those of A1 subjects. In one family, however, the A transferase detected is of the A1 type. On a quantitative level, the enzyme activities of these sera only reached 30-50 percent of the average value observed for A1 or A2 subjects, respectively. These facts suggest the existence of a genetic inhibitor, possibly linked to the ABO locus, preventing either an A1 or A2 gene from acting at the level of some cellular lines and leading therefore to the recognition of phenotypes named A-m-A1 and A-m-A2. On the contrary, under the experimental conditions used, no alpha-N-acetylgalactosaminyl-transferase activity was detected among the four individuals of the second group, named A-y by Weiner et al. (37), and whose appeareance in siblings results from the action of a recessive modifying y-A gene.

Adenosine Triphosphate↗
PubMed1975

A correction to the autoanalyzer data for quantitative agglutination measurements.

The AutoAnalyzer was used for quantitative measurements of antibody agglutinating activity by a Polybrene agglutination technique. Since the continuous flow system introduces an experimental error to the determination of true agglutination percentage, it is necessary to apply a correction factor. The experimental method of correction is described.

Autoanalysis↗