Molecular Genetics of Human Immune Responsiveness to Lolium perenne (Rye) Allergen, Lol p III (Short Communication)

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Abstract
Lol p II and III are each about 11-kD protein allergens from the pollen of Lolium perenne (rye grass). We have found that human immune responses (IgE and IgG antibodies) to both proteins are significantly associated with HLA-DR3. In addition, the two proteins are cross-reactive with the antibodies in many human sera (about 84% human sera showed the cross-reactivity). We have determined > 90% of the amino acid sequences of the two proteins and found that they are at least 54% homologous. Berzofsky found that 75% of the 23 known T cell sites in various proteins had an amphipathic structure. Our analysis by the same method showed that both Lol p II and III have a major region of amphipathicity (at residues 61–67, Lol p III numbering) which might contain sites for binding to an la molecule and a T cell receptor. This region is identical between Lol p II and III, except for an Arg-Lys substitution, and could account, in part, for the DR3 association with responsiveness to both molecules. An interesting difference between the two proteins is that immune response to Lol p III is associated with DR5 (in addition to DR3), whereas no DR5 association is found in the case of Lol p II. One possibility is that Lol p III has an additional site which binds to the DR5 la molecule. Lol p III indeed has a second highly amphiphathic peptide, 24–30 (Lol p III 24 R P G D T L A 30), which is different and not amphipathic in Lol p II. Therefore, the results of these analyses are consistent with our observations that DR3 is associated with immune responses to both Lol p II and III, but DR5 is associated with immune response to only one of them, Lol p III. Further experiments are required to examine these postulates.

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