We have developed sensitive amplified immunoassays for measurement of IgE and IgG4 ragweed (RW) antibodies in unconcentrated nasal washes. IgE to Amb a I (formerly antigen E) can be assayed to <0·1 ng/ml using IgE capture by anti-IgE on microtitre plates and an alkaline phosphatase-conjugated Amb a I with an amplification substrate technique. IgG4 to whole RW extract was assayed to <0·01 ng/ml by amplification ELISA using monoclonal anti-IgG4. Nasal washes (NW) (10 ml) and serum were obtained in December from 22 RW-sensitive patients before and after 1 and 2 yr of RW immunotherapy (IT), and assayed for Amb a I IgE or RW IgE and R W IgG4 antibodies. Amb a I IgE could be measured in the NW of 15/22 pre IT, 19/22 at 1 yr IT, but only 3/10 at 2yr IT (compared with pre-IT, P 0·05). Mean Amb a I IgE in NW was 0·66, 0·36 and 0·21 ng/ml at pre, 1 yr and 2 yr IT (P-values > 0·05). Mean serum RW IgE, was 76, 55 and 27 ng/ml at pre, 1 yr and 2 yr IT (P-values > 0·05). Amb a I IgE in nasal washes was correlated with RW IgE in serum (r=0·56, P <0·001, n=44). RW IgG4 was detectable in NW of 15/22pre-IT, 18/22 at 1 yr IT and 9/10 at 2 yr IT (P- values > 0·05). Mean serum RW IgG4 in NW did not change with IT (0·12, 0·16 and 0·20 ng/ml at pre, 1 yr and 2 yr IT, P-values > 0·05). whereas serum RW IgG4 rose substantially from a mean 23 ng/ml pre IT to 197ng/ml at 1 yr IT and 1324 ng/ml at 2 yr IT (P-values < 0·0001). Nevertheless, RW IgG4 in NW and serum was significantly correlated (r= 0·59, P 0·001, n= 44). We conclude that using sensitive immunoassays IgE and IgG4 RW antibodies can be measured in unconcentrated NW of about two-thirds of ragweed-sensitive patients. Both isotypes in NW have strong correlation with corresponding serum antibodies, but the significant rise of serum RW IgG4 after IT is not reflected in NW of asymptomatic subjects out of season. Whether allergic inflammation can increase IgG4 in NW remains to be determined.
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