Clinical Relevance

IgE-mediated reactions

Anecdotal evidence suggests that asthma and hay fever are possible following exposure to pollen from this tree; however, few specific studies on this have been reported to date.

Nasal and bronchial bald cypress challenges verify this tree’s ability to cause both allergic rhinitis and asthma. In a study in which 57 nasal and bronchial provocation tests were performed with bald cypress pollen extract on 41 subjects, a positive nasal response was elicited in 12 of 17 (71%) subjects with allergic rhinitis and positive bald cypress pollen skin tests. A positive bronchial challenge was elicited in 2 of 10 asthmatics with positive bald cypress pollen skin tests. Bald cypress-specific IgE was demonstrated in 7 of the 12 (59%) subjects with a positive nasal challenge, and in 1 of the 2 subjects with a positive bronchial challenge.

Both bald cypress and Japanese red cedar belong to the Taxodioideae family, and authors have suggested that bald cypress extract for immunotherapy will provide protection against both allergens.

Cross-Reactivity

he cypress family, Cupressaceae, is the most allergenic family in the order Coniferales. This family, which includes the sub-family Taxodioideae, contains cypress (Cupressus and Chamaecypris spp), cedar and juniper (Juniperus spp), bald cypress (Taxodium distichum), redwood and sequoia (Sequoia spp), and Japanese red cedar (Cryptomeria japonica). Members are strongly cross-reactive, with animal antisera and human IgE antibody studies demonstrating consistent cross-inhibition. Older literature has demonstrated the interchangeability of Cupressaceae member crude extracts. Strong homology has been demonstrated between the major (group 1) allergens of the various species. Although amino acid sequences are highly homologous among group 1 allergens, glycosylation sites may differ. Similarly, a study suggests that conserved homologs of the allergen Cry j 2 of the Japanese cedar tree confer cross-allergenicity among Taxodiaceae and Cupressaceae.

A study evaluated the residual serum samples of adult and paediatric patients with at least 1 positive allergen-specific IgE to a tree pollen (n = 102); testing with commercial reagents found 57 of 102 samples (56%) had bald cypress IgE of 0.1 kUa/L or higher, and 64 of 102 (63%) had red cedar IgE concentrations of 0.1 kUa/L or higher. All samples positive for bald cypress were also positive for red cedar. However, 7 patients (7%) had positive results for red cedar, with values ranging from 0.11 to 0.67 kUa/L, but were negative for bald cypress IgE (<0.10 kUa/L). Inhibition assays revealed that both the red cedar and bald cypress extracts readily inhibited the binding of IgE to the other allergen in a dose-dependent manner. The very similar and strong inhibitions by both bald cypress and red cedar suggest similar antigenic composition, but the 7 serum samples positive for red cedar and negative for bald cypress demonstrate at least one minor antigenic difference. The authors concluded that the results suggest that red cedar extract contains most of the allergens of bald cypress extract, and that testing for red cedar sensitivity will detect nearly all individuals who are sensitive to bald cypress.