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Biomedical subjects

K U Jansen

Publications and source records attributed to K U Jansen.

24 records · Page 2Linked to original sources
PubMed1992

CD21 is a ligand for CD23 and regulates IgE production.

The molecule CD23, a low-affinity receptor for IgE (Fc epsilon R2), is a type II transmembrane molecule expressed on many haemopoietic cell types. CD23 has pleiotropic roles in the control of lymphocyte behaviour, suggesting that CD23 may interact with another ligand in addition to IgE. To identify such a CD23 ligand, we expressed and purified full-length recombinant CD23, incorporated it into fluorescent liposomes and used these as a probe. We report here that fluorescent liposomes carrying CD23 interact specifically with the cell-surface protein CD21, identified as the receptor for Epstein-Barr virus and the complement receptor-2 on B cells, some T cells and follicular dendritic cells. In addition, fluorescent CD23-liposomes were shown to bind to hamster kidney cells (BHK-21) transfected with CD21 complementary DNA. The interaction between fluorescent CD23-liposomes and B cells or CD21-transfected BHK-21 cells was specifically inhibited by anti-CD21 and anti-CD23 monoclonal antibodies. Western blotting analysis revealed that 14C-labelled liposomes carrying CD23, in contrast to anti-CD21 antibodies, reacted with a subtype of CD21 molecules. Triggering of CD21 either with an anti-CD21 antibody or with recombinant soluble CD23 was shown to increase specifically interleukin-4-induced IgE production from blood mononuclear cells. These results demonstrate that the cell-surface protein CD21 is a ligand for CD23 and that the pairing of these molecules may participate in the control of IgE production.

Animals↗
PubMed1991

Recombinant 25-kDa CD23 and interleukin 1 alpha promote the survival of germinal center B cells: evidence for bifurcation in the development of centrocytes rescued from apoptosis.

Germinal centers contain a proliferating pool of centroblasts which give rise to non-dividing centrocyte. Centrocytes are programmed to die by apoptosis unless they receive a positive signal for rescue. Rescue, in vivo, is likely to be dependent, initially, on interaction with antigen held on follicular dendritic cells (FDC). A subset of FDC located in that part of the germinal center furthest from centroblasts is particularly rich in CD23. Supernatants containing high levels of soluble CD23 were found not only to encourage the survival of germinal center B cells but also to promote their differentiation toward a plasmacytoid morphology; these activities were diminished following removal of CD23 from the supernatants. Recombinant 25-kDa CD23 was initially found to be incapable of providing the signal for germinal center cell development but on the addition of interleukin 1 alpha which, by itself, was inactive, rescue and differentiation of germinal center B cells were now achieved. Apoptosis in germinal center cells could also be prevented by the ligation of surface CD40 with monoclonal antibody: however, rescue via this pathway was not accompanied by plasmacytoid differentiation. These findings provide a functional rationale to the high level expression of CD23 found within a discrete subset of FDC and indicate a bifurcation in the development of germinal center B cells following their rescue from apoptosis.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1991

Expression of human recombinant CD23 in insect cells.

Human CD23 (low affinity receptor for IgE) has been expressed in insect cells (Sf9) using the baculovirus expression system and the baculovirus transfer vector pAc373. Insect cells infected with a recombinant baculovirus coding for CD23 synthesized a polypeptide not found in wild-type infected insect cells that had antigenic properties similar to natural CD23 produced in RPMI 8866 cells. Surface expression of recombinant CD23 was demonstrated by its ability to bind IgE. Recombinant CD23 expressed in insect cells had a slightly lower molecular weight (43 kDa) than that of natural CD23 (45 kDa) from RPMI 8866 cells as detected by SDS-PAGE followed by Western-blotting. Affinity-purified recombinant CD23 from infected insect cells showed B-cell growth promoting activitiy. These observations demonstrate for the first time that biologically active recombinant CD23 can be produced by the baculovirus expression system, thus providing a useful source of recombinant material to elucidate the biological functions of CD23.

Animals↗
PubMed1989

Expression of the four subunits of the Torpedo californica nicotinic acetylcholine receptor in Saccharomyces cerevisiae.

Yeast expression vectors were constructed containing complementary DNA encoding the alpha-, beta-, gamma-, and delta-subunits of the Torpedo californica nicotinic acetylcholine receptor under the control of the Saccharomyces cerevisiae alcohol dehydrogenase promoter. All four plasmids were integrated into the yeast genome of a single yeast cell. The resulting yeast strain synthesized polypeptides novel to yeast that had the molecular weights and antigenic properties similar to the authentic T. californica receptor alpha-, gamma, and delta-subunits. The beta-subunit polypeptide could not be detected in this yeast strain, even though the poly(A)+ RNA from this strain contained all the information necessary for the expression of functional acetylcholine receptors in Xenopus laevis oocytes. The replacement of the beta-subunit mRNA 5'-untranslated leader and its N-terminal signal sequence by the corresponding alpha-subunit sequences, however, resulted in the expression of the beta-subunit polypeptide in yeast grown at 5 degrees C.

Animals↗