Pollen allergen Phl p 5 (Phl p 5)

The pollen allergen Phl p 5 from *Phleum pratense* (timothy grass) is a major respiratory allergen recognized by IgE antibodies in 65-90% of grass pollen-allergic individuals, making it a key marker for genuine sensitization alongside Phl p 1. This small protein (approximately 29-38 kDa) features a unique structure with two domains forming a protease-resistant four-helix bundle, high alanine content (26 mol%), and multiple independent conformational IgE epitopes—up to four clusters—that explain its potent ability to trigger severe allergic symptoms like rhinitis and asthma. Isoforms such as Phl p 5a, Phl p 5b, Phl p 5.0101, and Phl p 5.0201 show structural variations, including differences in N- and C-terminal epitopes, leading to individual patient reactivity patterns and cross-reactivity with other Pooideae grasses. While not a therapeutic target like receptors or enzymes, Phl p 5 serves in diagnostics and allergen immunotherapy, with recombinant forms used to map epitopes and assess sensitization. Its high-density IgE recognition underscores challenges in desensitization therapies due to epitope diversity and histamine-releasing potency.

Other names

Phl p VGroup 5 allergenPhl p 5aPhl p 5bPhl p 5.0101Phl p 5.0201Phl p 5.0207