A human monoclonal antibody to a human self-antigen, CD2 derived from human peripheral blood lymphocytes engrafted in SCID mice.

To establish human hybridoma lines, production of human immunoglobulin (Ig) and behavior of the implanted human peripheral blood lymphocytes (PBL) were characterized in severe combined immunodeficiency (SCID) mice. Human PBL from healthy donors were injected into the peritoneal cavity of SCID mice, and they were immunized with self-antigen, CD2. CD45+ cells (human PBL) migrated to lymphoid tissues in the mice as early as 4 days, accounting for more than half the lymph node cells and thymocytes.

Significance of soluble Fc epsilon receptor II (sFc epsilon RII/CD23) in serum and possible application of sFc epsilon RII for the prevention of allergic reactions.

The significance of sFc epsilon RII in IgE-mediated allergic disease was examined. sFc epsilon RII in serum was found to decrease following clinical improvement, suggesting sFc epsilon RII in serum may be an indicator of allergic diseases. Significant proportions of sFc epsilon RII in serum were present as complexes with IgE in normals as well as in atopic patients, and these complexes were more prominent in the former than in the latter group.

Recombinant soluble Fc epsilon receptor II (Fc epsilon RII/CD23) has IgE binding activity but no B cell growth promoting activity.

We have undertaken the production of recombinant soluble Fc epsilon receptor II (Fc epsilon RII) as a secretory protein, but not as a cleavage product of membrane-bound receptor. Several plasmid constructs containing soluble receptor sequence were prepared. Only a chimeric gene containing the sequences encoding IL-6 signal peptide and the soluble moiety of Fc epsilon RII could be expressed in Xenopus laevis oocytes and CHO cells, resulting in the secretion of soluble Fc epsilon RII.

Structure and function of Fc epsilon receptor II (Fc epsilon RII/CD23): a point of contact between the effector phase of allergy and B cell differentiation.

The Fc epsilon receptor II (Fc epsilon RII/CD23) has been proposed to have multiple functions as a membrane-bound or soluble molecule: a function in B cell growth and differentiation and a role in the effector phase of IgE-mediated immunity. We recently demonstrated the presence of two forms of Fc epsilon RII (Fc epsilon RIIa and Fc epsilon RIIb) whose structures differ only at their N-terminal cytoplasmic regions. The regulatory mechanisms of their expression strongly suggest that Fc epsilon RIIa and Fc epsilon RIIb function in B cells and in the effector cells of IgE-mediated immunity, respectively.

Molecular structure of human lymphocyte receptor for immunoglobulin E.

We have isolated and sequenced a cDNA clone encoding the human lymphocyte receptor for IgE (Fc epsilon R). The deduced protein sequence reveals that Fc epsilon R consists of 321 amino acids, without any signal sequence, and is oriented with its N-terminus on the cytoplasmic side and its C-terminus on the outside of the cell. This molecule shows striking sequence homology with chicken asialoglycoprotein receptor (hepatic lectin), suggesting a possible role for Fc epsilon R in endocytosis.