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Biomedical subjects

R I Zuberi

Publications and source records attributed to R I Zuberi.

6 recordsLinked to original sources
PubMed1992

Biochemical and biophysical characterization of human recombinant IgE-binding protein, an S-type animal lectin.

IgE-binding protein (epsilon BP) was originally identified by virtue of its affinity for IgE. It is now known to be a beta-galactoside-binding lectin with the characteristic of an S-type carbohydrate recognition domain. The protein is composed of two domains: the amino-terminal domain consisting of tandem repeats and the carboxyl-terminal domain containing sequences shared by other S-type carbohydrate recognition domains. The amino-terminal domain also contains a number of potential recognition sites for collagenase cleavage. In this study, human epsilon BP was first expressed in Escherichia coli, and the carboxyl-terminal domain (epsilon BP-C) was then generated by collagenase digestion of epsilon BP. By equilibrium dialysis, the association constants of epsilon BP and epsilon BP-C for lactose were found to be similar (6.0 +/- 0.70) x 10(4) M-1 and (4.7 +/- 0.27) x 10(4) M-1, respectively. Both polypeptides contain only one lactose-binding site/molecule. By an assay involving binding of 125I-labeled epsilon BP or epsilon BP-C to solid phase IgE, and inhibition of this binding by saccharides, it was determined that epsilon BP-C retains the saccharide specificity of epsilon BP. Importantly, although unlabeled epsilon BP-C inhibited the binding of the radiolabeled epsilon BP to IgE, unlabeled epsilon BP caused increased binding to IgE, suggesting self-association among epsilon BP molecules. Oligomeric structures resulting from self-association of epsilon BP were confirmed by chemical cross-linking studies. Furthermore, epsilon BP possesses hemagglutination activity on rabbit erythrocytes, whereas epsilon BP-C lacks such activity. Based on these results, we propose a structural model for multivalency of epsilon BP: dimerization or oligomerization of epsilon BP occurs through intermolecular interaction involving the amino-terminal domain.

Animals↗
PubMed1992

Activity of defensins from human neutrophilic granulocytes against Mycobacterium avium-Mycobacterium intracellulare.

We have examined the activity of defensins from human neutrophilic granulocytes against Mycobacterium avium-Mycobacterium intracellulare. M. avium-M. intracellulare at 2.5 x 10(6)/ml or 2.5 x 10(8)/ml was cultured in the presence of defensins at 37 degrees C from 4 to 48 h. After incubation, CFU were enumerated. Human neutrophil peptide 1 (HNP-1) at 5 micrograms/ml had the ability to kill M. avium-M. intracellulare. Treatment with HNP-1 resulted in significant (96.3 to 97.7%) killing of M. avium-M. intracellulare, even after taking clumping into consideration. This activity was not affected by the presence of calcium (0.5 and 1.0 mM), magnesium (0.5 and 1.0 mM), or sodium chloride (25, 50, and 100 mM). The optimal pH for bactericidal activity was higher than 5. We tested numerous M. avium-M. intracellulare strains, and HNP-1 was successful in killing every strain, although the degree of killing varied among them (34.2 to 87.2%). Additionally, this activity was independent of colonial morphology. We also examined the activity of HNP-2 and HNP-3 against M. avium-M. intracellulare and found that they were as effective in killing M. avium-M. intracellulare as HNP-1 was. These observations suggest that defensins may play an important role in the host defense against M. avium-M. intracellulare.

Blood Bactericidal Activity↗
PubMed1988

Production of IL-1-mimicking anti-idiotypic antibodies in rabbits in response to IL-1 immunization.

This report describes the characterization of immunoglobulins with interleukin-1 (IL-1)-like activity from the serum of rabbits immunized with partially purified mouse IL-1. Early after immunization, immune sera were found to contain anti-IL-1 antibodies (idiotypes) that inhibited IL-1 bioactivity (augmented-proliferation of PHA-stimulated thymocytes). Later, anti-idiotypic antibodies appeared that mimicked IL-1 activity. These IL-1-like antibodies were affinity purified either on an anti-IL-1-enriched Ig-Sepharose 4B column from an early bleed or sequentially on anti-Ig and Protein A immunoadsorbent columns. By ELISA anti-idiotypic antibodies specifically bound to rabbit anti-IL-1 antibodies. Functionally, IL-1 mimicking antibodies were reproducibly effective in augmenting the in vitro proliferation of PHA-stimulated thymocytes or Con A-stimulated D10 cells. On the other hand, they did not support proliferation of the IL-2-dependent CTLL-2 cells. The ability of IL-1-mimicking antibodies to enhance thymocyte proliferation could be blocked by functional site related anti-IL-1 antibodies. By Western blot, 125I-labeled IL-1 and IL-1-mimicking antibodies bound to a similar 23 Kd mol. wt protein material recovered from the lysate of thymocytes stimulated with PHA for 48 h. That the observed bioactivity could be attributed to antibody molecules and not to contaminant IL-1 was ascertained by several methods, namely (1) SDS-PAGE analysis of 125I-labeled material and (2) resistance to loss of bioactivity by lyophilization. Furthermore, as neither Ig-anti-Ig nor BSA-anti-BSA complexes mimicked IL-1-augmented thymocyte proliferation, a non-specific effect due to immune complexes could be excluded. The occurrence of antibodies mimicking several of the IL-1 functions induced following IL-1 immunization suggests a potential role for the idiotypic network in modulating cytokine activities and a possible link between regulation of the immune system by cytokines and immunoglobulin idiotypes.

Animals↗
PubMed1988

Antigenic differences between natural and recombinant murine IL-1.

Natural (n) interleukin 1 (IL-1) and recombinant (r) IL-1 alpha of murine P388D1 cell line origin were investigated for their antigenicity in rabbits. Both nIL-1 and rIL-1 alpha evoked an antibody response. By solid-phase radioimmunoassay, anti-nIL-1 antibodies bound nIL-1 and rIL-1 alpha equally well; in contrast, the anti-rIL-1 alpha antibodies bound homologous rIL-1 alpha significantly more than nIL-1 suggesting either a lack of antibodies directed against certain epitope(s) on nIL-1 or presence of low affinity antibodies. Moreover, unlike anti-nIL-1 antibodies, anti-rIL-1 antibodies failed to inhibit augmentation of thymocyte proliferation by either IL-1. Thus, antigenic differences between nIL-1 and rIL-1 alpha appear to elicit an overlapping but different antibody response in rabbits.

Animals↗