A glycoprotein (BLA.36), expressed on the plasma membrane of Hodgkin's cells and also on normal and malignant B lymphocytes and histiocytes, was identified by reaction with a monoclonal antibody. BLA.36 was not detectable on other hematopoietic, carcinoma or melanoma cell lines. BLA.36 was purified to homogeneity by extracting proteins from a Hodgkin's cell line (HDLM-3), followed by immunoaffinity chromatography, utilizing immobilized anti-BLA.36 antibody, and gel filtration on Sephacryl S-100 in the presence of protein dissociating agents. The purified component yielded a single band on sodium dodecyl sulphate/polyacrylamide gel electrophoresis under both non-reducing and reducing conditions, and closely related three isotypes of similar molecular weight and with the apparent isoelectric points that ranged from 5.0 to 5.2 on two-dimensional gel electrophoresis. The purified BLA.36 reacted with the original specific antibody, on both one- or two-dimensional gel electrophoresis, suggesting that antigenic determinant was not adversely affected during purification procedure. Competitive immunoprecipitation analyses and the determination of N-terminus sequence of the first 13 amino acid residues suggest that BLA.36 is unrelated to other known Hodgkin's or hematopoietic cell antigens. Finally, significance of BLA.36 expression on the growth of BLA.36-positive cell lines was studied. Blocking of BLA.36 with anti-BLA.36 antibody led to the in vitro growth-inhibition of BLA.36-positive cell lines. The antibody pre-absorbed with the purified BLA.36 was unable to exert growth-inhibition, demonstrating the specificity of reaction. In addition, the treatment of the BLA.36-positive cell lines with differentiation-inducing agent, alpha-interferon (alpha-IFN), down-regulated BLA.36 expression and also showed in vitro growth-inhibition of BLA.36-positive cell lines. Taken together, these results suggest a growth-related function of BLA.36.
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