CHARACTERIZATION OF THE ISOFORMS OF THE GROUP-I ALLERGEN OF CYNODON-DACTYLON

Background: The group I allergen of Cynodon dactylon, Cyn d I, was fou nd to consist of four to 10 isoforms. Methods: We studied the isoforms with the use of two-dimensional gel electrophoresis. The antigenic di fference of the isoforms was evaluated by radioimmunoprecipitation wit h monoclonal antibodies (MAbs). The acidic isoforms and the basic and neutral isoforms were further isolated by MAb-affinity chromatograghy for RAST and competitive RAST In addition, the N-terminal sequence was evaluated by microsequencing. Results: A total of 11 isoforms were fo und in Cyn d I in extracts prepared from different sources of Bermuda grass pollen (BGP). They were either acidic (Cyn d I-A, I-B, I-C, I-D, I-E, I-F, I-G, I-H, and I-I), neutral (Cyn d I-X), or basic (Cyn d I- J). Cyn d I-G, with an isoelectric point of approximately 6.4, was con stantly present in all the pollen preparations, whereas the content of the basic Cyn d I-J varied from less than 5% to greater than 20%. The molecular weight of the basic and neutral isoforms were slightly lowe r than those of the acidic isoforms. All isoforms shared a common anti genic determinant(s) recognizable by MAb 4-37, and the basic and neutr al isoforms possessed a unique antigenic determinant(s) recognizable b y MAb 1-61. RAST showed that both the acidic Cyn d I and the basic and neutral Cyn d I were recognized by human IgE in the pooled sera of pe rsons allergic to BGP. Competitive RAST showed a high crossreactivity between the acidic and the basic and neutral isoforms. A 95% sequence identify also existed between the N-terminal 20 amino acid residues of basic Cyn d I-J and the dominant acidic isoform Cyn d I-G. Conclusion s: We present study disclosed that basic Cyn d I-J is an important all ergen and that the content of this isoform varies in different lots of BGP.