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J Urbain

Publications and source records attributed to J Urbain.

At least 145 records · Page 8Linked to original sources
PubMed1976

Common origin and evolution of variable and constant regions of immunoglobulins.

Sequence data show that the immunoglobulins evolved from two sets of paralogous genes: a gene set coding for the V regions and another for the different C regions. A comparison of sequences from these two gene sets shows homology between the V and C sets of genes: this homology is only significant when VH is compared with Cmu1, Cmu2 and Cgamma1. There is a close agreement between our data drawn from sequence comparisons and the data of Poljak et al. (1974) drawn from crystallographic data. This finding is in agreement with the results of the phylogenetic trees of the C and V gene sets: they suggest that the VH subgroups and the first constant domain of the heavy chains are the most ancient. Moreover homology between the red blood cell glycophorin and Cmu2 suggests that immunoglobulins could have a common origin with some membrane proteins.

Amino Acid Sequence↗
PubMed1975

Linear and inverted repetitions in protein sequences.

An extensive search for internal regularities in amino acid sequences has been made, using both the genetic code and the relative frequencies of amino acid alternatives in homologous proteins. The two methods give very similar results and strongly suggest the occurrence of significant linear and inverted repetitions (similar sequences of opposite polarity) in several proteins. A hypothesis is developed to explain the occurrence of such internal regularities in proteins. This hypothesis is based on a process of duplication of an ancestral loop in which a symmetrical arrangement of amino acid allows stabilization by interaction between the amino acid side chains.

Amino Acid Sequence↗
PubMed1975

Sharing of idiotypic specificities between different antibody populations from an individual rabbit.

Rabbits hyperimmunized with tobacco mosaic virus synthesize very heterogeneous antibodies. Despite this, specific anti-idiotypic sera recognizing a large part (70%) of these antibodies can be raised in rabbits matched for allotypic specificities a1, a2, a3, b4, b5, b6, c7, and b9. Different rabbits synthesize antibodies with different idiotypic specificities. However, in the serum of a single rabbit antibody fractions of different isoelectric pH share some idiotypic specificities. The results show that, at least in certain cases, antibodies against one antigen are not simply a random collection of immunoglobulin which happen to fit with this antigen, but that some definite relationship exists between the products of different clones which have been activated by antigen. These findings are discussed in the light of network concepts of the immune system.

Animals↗
PubMed1975

Importance of short-lived lymphocytes in the immune response.

Lymphocytes are heterogeneous with respect to their life-span. Typical B cells, bearing on their membranes immunoglobulin receptors, easily detectable by immunofluorescence, belong mainly to the long-lived population: this can be observed using combined autoradiography and immunofluorescence. However, when primed mice receive (-3H) thymidine before a boosting injection of tobacco mosaic virus (TMV), many plasma cells appearing in the spleen during the secondary response are labelled. In irradiated recipients repopulated with spleen cells from donors primed with TMV and injected with tritiated thymidine 2 hours before killing, the majority of plasms cells appearing in the spleen after antigen injection were labelled. If irradiated mice were repopulated simultaneously with spleen cells from donors primed with TMV and injected with (-3H) thymidine, and from donors primed with haemocyanin, most of the anti-TMV plasms cells were labelled, while most of the anti-haemocyanin plasma cells were unlabelled. These results allowed us to exclude non-specific reutilization of labelled thymidine as the main reason of our observations. It is concluded that either plasma cells derive from shortlived precursors or they receive material from a labelled cell able to co-operate specifically with plasma cell precursors.

Animals↗
PubMedDate not supplied

Idiotypic lymphocytes in human monoclonal gammopathies.

We have studied seven human monoclonal gammopathies using anti-idiotypic sera. In benign and malignant gammopathies, we have observed a similar number of B lymphocytes bearing idiotypic specificities also found on the monoclonal protein. These observations suggest that the plasma cell population is only a phenotypic expression of a tumoral event occurring in a B lymphocytes precursor which can still completely differentiate. In four myeloma patients and one benign monoclonal gammopathy, we also observed T lymphocytes bearing receptors idiotypically cross-reactive with the monoclonal protein. The values ranged from 1.8 to 8.0% within the purified T-cell population. In a first hypothesis, these T lymphocytes can belong to the tumoral clone itself. The tumoral event must occur at the level of a common precursor not yet determined to B or T pathway of differentiation. In a second hypothesis, these T lymphocytes are not cancerous but are induced by a strong perturbation of the idiotypic network, due to the enormous amount of the idiotypic B-cell tumoral subset.

B-Lymphocytes↗
PubMedDate not supplied

Oncoselective transduction of CD80 and CD86 in tumor cell lines using an autonomous recombinant parvovirus.

BACKGROUND: The aim of this study was to enhance selectively the immunostimulatory properties of tumor cells. Based on their oncotropic properties, we used autonomous recombinant parvoviruses to transduce the genes coding for the constimulatory molecules CD80 (B7-1) or CD86 (B7-2) specifically into tumor cells without transducing normal cells. MATERIALS AND METHODS: After infection of tumor cells by these viruses, surface expression of CD80 and CD86 molecules was assessed by FACS and enhancement of immunostimulatory properties was assessed in alloreactions with G-10 purified T cells. RESULTS: Infection of normal and transformed cells with recombinant MVM- B7-1 or B7-2 viruses leads to expression of costimulatory molecules only by tumor cells and confers on them the capacity to sensitize naive T cells in vitro. CONCLUSION: This approach should ultimately lead to selective expression of costimulatory molecules in tumor tissues in vivo without affecting normal cells.

Animals↗