<p>Grass pollens are a major cause of type I allergy. Lol pI, the major rye grass (Lolium perenne) allergen, is a 240-amino acid protein [<cite idref="PUB00002579"/>]. Analysis of the amino acid sequence has revealed a determinant within the Lol pI molecule that is recognised by human leukocyte antigen class II-restricted T cells obtained from patients allergic to rye grass pollen [<cite idref="PUB00002579"/>]. </p><p>Sequence analysis of a pollen-specific cDNA from maize has revealed a homologue (Zea mI) of the Lol pI gene [<cite idref="PUB00001833"/>]. The protein is ~70% similar to the reported amino acid sequence of Lol pIA. Southern analysis indicates Zea mI to be a member of a small multigene family in maize. Northern analysis indicates expression only in pollen, not in vegetative or female floral tissues. The timing of expression is developmentally regulated,occurring at a low level prior to the first pollen mitosis, and at a high level after post-meiotic division [<cite idref="PUB00001833"/>]. </p> Major pollen allergen Lol pI