Binding site for IgE of the human lymphocyte low-affinity Fc epsilon receptor (Fc epsilon RII/CD23) is confined to the domain homologous with animal lectins.
AUTOR(ES)
Bettler, B
RESUMO
The lymphocyte low-affinity receptor for IgE (Fc epsilon RII) is involved in two seemingly unrelated processes: (i) promotion of general B-cell growth and (ii) isotype-specific IgE synthesis. To characterize domains of Fc epsilon RII important for effector function, we have expressed Fc epsilon RII mutants in mammalian cells. The results show that the IgE-binding region of Fc epsilon RII corresponds almost exactly to a domain of 123 amino acid residues homologous with the carbohydrate-binding domain of C-type animal lectins. With the recent demonstration that Fc epsilon RII binds to IgE independently of any lectin-like activity [Vercelli, D., Helm, B., Marsh, P., Padlan, E., Geha, R.S. & Gould, H. (1989) Nature (London) 338, 649-651], it is now clear that, in this case, the lectin module has evolved to interact with a protein rather than a carbohydrate moiety. The epitopes of several independent monoclonal antibodies that inhibit the binding of IgE to Fc epsilon RII are clustered within the lectin-like domain. Some of these antibodies are also known to suppress, isotype-specifically, the interleukin 4-promoted IgE synthesis from peripheral blood mononuclear cells or the spontaneous synthesis of IgE by B cells isolated from atopic donors. The epitope of MHM6, an anti-F epsilon RII monoclonal antibody delivering an epitope-restricted growth-promoting effect on B cells, is also located within the lectin-like domain. Thus, the lectin module of Fc epsilon RII not only acts as a carbohydrate-independent, isotype-specific Fc receptor but may also participate in the general regulation of B-cell growth.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=298006Documentos Relacionados
- Alpha-helical coiled-coil stalks in the low-affinity receptor for IgE (Fc epsilon RII/CD23) and related C-type lectins.
- Molecular structure and expression of the murine lymphocyte low-affinity receptor for IgE (Fc epsilon RII).
- Low-affinity IgE receptor (CD23) function on mouse B cells: role in IgE-dependent antigen focusing.
- Physical association between the high-affinity IgG receptor (Fc gamma RI) and the gamma subunit of the high-affinity IgE receptor (Fc epsilon RI gamma).
- Human lymphocyte Fc receptor for IgE: sequence homology of its cloned cDNA with animal lectins.