Abstract
Monoclonal antibodies, 1-7, 3-5 and 8-30, specific to Fcε receptor (FcεR) on human B cells were established. The two monoclonals (1-7 and 8-30) were directed to the IgE binding site of FcεR, and the other monoclonal (3-5) recognized the same molecules, but a different epitope. The molecules recognized by these monoclonals had M.W. of 46 Kd. as determined by SPS-PAGE analysis.
By employing these monoclonals, the distribution of FcεR+ cells was studied in various lymphoid tissues, and the results showed that FcεR is a B cell specific differentiation marker confined to matur μ+δ+ B cells and disappear after class-switching. The lymphokine respensible for FcεR expression was BSF-1 (IL-4) . It was also found that FcεR expression on peripheral B cells was much augmented in atopic patients than normals.
We isolated and sequenced a cDNA clone encoding the FcεR. The deduced protein sequence revealed that FcεR consists of 321 amino acids, and is oriented with its N-terminus on the cytoplasmic side and its c-terminus on the outside of the cell. This molecule showed striking sequence homology with chicken asialoglycoprotein receptor, suggesting a possible role for FcεR in endocytosis.
