Which grasses are most likely to cross-react with timothy pollen?

The choice of bluegrass, rye, and fescue as grasses most likely to cross-react with timothy pollen is based on the botanical and allergenic similarities they share. Timothy grass (Phleum pratense) is part of the Poaceae family, which includes a variety of grass species that often share similar protein structures.

Bluegrass (Poa pratensis), rye (Secale cereale), and fescue (Festuca spp.) contain allergenic proteins that may trigger similar immunological responses in susceptible individuals because their pollen proteins can be structurally similar to those found in timothy grass pollen. This similarity can lead to cross-reactivity, where individuals allergic to one type of pollen—like that from timothy grass—may also have allergic reactions to the pollen of these other grasses.

In contrast, the other options do not present the same likelihood of cross-reactivity with timothy pollen due to genetic and protein structure differences among those species. Therefore, the association of bluegrass, rye, and fescue with timothy grass regarding cross-reactive allergens is well-supported by research in allergenicity in pollen and the shared traits among the grasses in question.