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E Conway de Macario

Publications and source records attributed to E Conway de Macario.

17 recordsLinked to original sources
PubMed1979

Deficiency of high-affinity anti-beta-D-galactosidase antibodies in selected low immune responder mice.

Amount and affinity of anti-beta-D-galactosidase-activating antibodies (AAb) were studied in two lines of mice obtained by selective breeding for antibody response to heterologous erythrocytes. These lines, referred to as high (H) and low (L) lines, differ also in their responses to many antigens. Concerning AAb amounts, the maximal titer in H mice is higher than in L mice. However, the AAb levels in H mice decreased with increasing immunizing doses and became lower than in L mice for the highest dose. This fact can be explained in terms of intramolecular competition or suppression. Whereas the usual maturation pattern was observed in H mice, no AAb of high affinity were found in L mice, even after a minimal immunizing dose. At any dose tested, no maturation of AAb occurred until three months after immunization. This deficiency may be ascribed to B lymphocyte or macrophage modifications. A correlation between the deficiency of high-affinity AAb in L mice and their genetically induced low antibody responsiveness cannot be proved.

Animals↗
PubMed1979

Specific inhibition of the antibody-mediated activation of a defective beta-D-galactosidase by circulating activating epitope-binding molecules.

Activation of a defective Escherichia coli beta-D-galactosidase by specific activating antibody is inhibited competitively by a molecule with immunoglobulin properties but devoid of activating capacity. This molecule is found in the serum of nonimmunized rabbits and is no longer detectable after beta-D-galactosidase administration, but can be demonstrated in rabbits injected with antigens other than the enzyme. The data show that the inhibitory molecule recognizes and interacts specifically with the activating epitope of the activatable enzyme and that, although unable to activate the latter, it competes with the activating antibody and inhibits activation.

Animals↗
PubMed1978

Antibody-mediated activation of a defective beta-D-galactosidase: dimeric form of the activatable mutant enzyme.

Sedimentation analyses of AMEF, an activatable mutant beta-D-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23), and the products of its reaction with Fab fragments of activating antibody show that this enzyme exists mainly as 10S dimers. Activation of AMEF by purified antibody resulted in formation of 16S tetramers. A unifying hypothesis postulating a dimer--tetramer equilibrium accounts for this observation as the counterpart of inactivation, which was shown to involve the breakdown of tetramers into inactive subunits [Roth, R. A. & Rotman, B. (1975) Biochem. Biophys. Res. Commun. 67, 1382--1390]. Conditions are described under which AMEF loses the specific antigenic determinant(s) responsible for binding activating antibody, allowing its subsequent use as an absorption to obtain immunologically purified activating antibody,

Antibodies↗
PubMed1978

Long-term antibody synthesis in vitro. VI. Anti-allotype sera as probes of clonal products in affinity maturation.

A new experimental system is described for measuring the allotypic product of rabbit B cells during long-lasting in vitro antibody responses. The immunoenzymatic assays described allow determination of several parameters mapping in different regions of the same molecule, which can be measured and combined to yield a multidimensional picture of the time-course dynamics of antibody synthesis. The rabbit immune system responding to Escherichia coli beta-D-galactosidase was sample and disassembled by (a) culturing lymph node microfragments and (b) sorting out from among all anti-enzyme antibodies only those activating a mutant enzyme, AMEF, which bore the b4 or b9 allotype. A considerable simplification of the response was achieved in the microcultures as documented by cultures of heterozygous cells which produced only one allotype and by the fact that each culture showed a distinctive pattern when antibody titre, association constant, heterogeneity index, L-chain type, and k-chain allotype were considered together. This array of patterns was not an artifact but the result of disassembling a representative sample of the rabbit immune system into small components, since the b4/b9 ratio obtained by averaging the results of all cultures from a heterozygous rabbit lymph node was the same as the serum ratio. Despite the Poisson distribution of the responder microcultures, none of them was monoclonal; i.e. no antibodies homogeneous by all parameters tested were observed, This finidng supports the notion that in normal lymphoid tissue in its native tridimensional arrangement, one T cell can trigger several B cells clustered in one antibody-forming unit. This natural arrangement would ensure the monospecificity of the cluster (dictated by the T cell) while allowing for variation in affinity (depending upon the array of B cells in the unit). Accordingly our findings would results from the fact that as the size of the microfragments was reduced, the cells diluted out first were T cells, but as long as one of them was present, several B-cell clones were triggered. The b4/b9 pattern of any given culture remained constant over several months, but the ratio kappa/lambda underwent changes. An increase in molecules with non kappa-chains (which could not be reacted with anti-kappa-chain allotype antisera) was usually associated with a parallel decrease in antibody affinity. This occurred by the end of the antibody cycle and might be related to the regulation of antibody synthesis by T-cell suppressor factors.

Animals↗
PubMed1978

Enhancement and inhibition of immunological mechanisms by immunosuppressive agents. I. Dose effect on priming and generation of memory to a bacterial antigen.

A new experimental system is described which allows the study of the effect of immunosuppressors upon the priming and generation of memory to an antigen from Escherichia coli. A single dose of bacterial beta-D-galactosidase without adjuvant injected into C57B1/6J mice primes and elicits memory but not antibodies. Thus by administering immunosuppressors near the priming injection, one can examine whether primary antibody formation is enhanced and whether priming generation of memory is enhanced or inhibited. We found that X-rays, cyclophosphamide and oxisuran (2-[(methylsulfinyl)acetyl]pyridine) either enhance or inhibit the elicitation of memory, depending on dosage, although they do not alter primary antibody unresponsiveness. The data show two main features: (a) immunosuppressors can enhance immunization; and (b) generation of memory can be improved without increasing antibody levels. The former finding draws attention to the role that immunosuppressors might play in the breaching of tolerance to self-antigens which share determinants with microbes, while the latter observation shows that antibody synthesis and elicitation of memory can follow independent pathways.

Animals↗
PubMed1976

Long-term antibody synthesis in vitro- IV. Independent segregation of antibodies directed to different determinants of an antigen molecule in its native configuration.

Independent segregation of antibody populations directed to different portions of E. coli beta-d-galactosidase occurs during the immune response against the enzyme. Anti-enzyme antibodies able to interact and activate a naturally occurring ligand, the mutant-defective enzyme AMEF (Antibody Mediated Enzyme Factor), do not parallel anti-enzyme antibodies which are measured by a coprecipitation assay involving precipitation of the wild-type molecule. Dissociation of the two antibody populations is best achieved in microcultures sustaining long-lasting responses. Similarly, anti-NIP (4-hydroxy-3-iodo-5-nitrophenylacetic acid) antibodies could be elicited without concomitant synthesis of anti-carrier antibodies by short-term challenge in vitro of ovalbumin-NIP-primed lymph nodes with a heterologous conjugate in which the hapten NIP was coupled to a carrier known to be non-immunogenic under the conditions of challenge. The potential applications of these findings are indicated, namely: large-scale production of monospecific antibodies in vitro; and the possibility of studying the regulatory role of antibodies directed towards on portion of the immunogenic molecule on the response to other regions of the same molecule.

Animals↗
PubMed1975

Long-lasting in vitro immune response to a distinct antigenic determinant of a bacterial protein. Cyclic changes of antibody titer and affinity.

Long-lasting (60 days or more) antibody responses in vitro by rabbit lymph node fragments to a distinct determinant of Escherichia coli beta-D-galactosidase were obtained by supplementing culture medium with fetal calf and horse serum. Antibodies released in the supernatant were removed every 3rd to 5th day together with the spent medium, without pooling to minimize intermixing of molecules synthesized far apart in time. Antibody titer, association constant, and heterogeneity index were measured in medium samples collected throughout the response in order to draw profiles of their changes under conditions whereby a limited number of clones synthesize antibodies in a closed system without connection to antigen depots, central lymphoid organs, and circulating cell and antibody pools. It was found that antibody affinity changes cyclically and that such cycles may be repeated. Cycles are composed of an ascendant limb with a gradual increase in affinity and a parallel diminution of heterogeneity. A descendant limb follows with the opposite modifications. High affinity antibodies predominate at the peak of the cycles, whereas low affinity molecules take over at the end of the cycles until the next ascendant limb begins; these persist after the last cycle has waned.

Animals↗
PubMedDate not supplied

New bioassay for screening immunotoxic agents.

A new bioassay for evaluation of compounds potentially toxic for the immune system is described. It is suitable for the measurement of enhancement of primary antibody response and of enhancement and inhibition of memory development in vivo. It utilizes immunoenzymatic techniques which can readily be automated and thus allow the screening of many compounds at relatively low cost. It can provide answers regarding the safety or danger of each compound tested within 30-45 days.

Animals↗
PubMedDate not supplied

[Asynchronism in the synthesis of antibodies directed against different antigenic sites of a macromolecule].

"Activating" and "precipitating" antibodies elicited by Escherichia coli beta-D-galactosidase can be isolated by assortment of the respective antibody-forming cells in vitro, showing that the two antibodies have different specificities. Both populations also segregate in vivo and are synthesized asynchronously. The interplay of different antibody species with the same immunogenic molecule and the role of these expected to be complex interactions in the regulation of the immune response is an area for further investigation.

Animals↗