IgG to various beta-glucans in a human adult population.

BACKGROUND: Fungal ß-(1,3)-glucans are pro-inflammatory agents, and exposures to ß-(1,3)-glucans are associated with respiratory tract symptoms. IgG anti-(1,3)-glucan titers are measured in diagnosis of fungal infections. Although other ß-glucan structures exist, like ß-(1,6)-glucans, little is known about their antigenic or pro-inflammatory properties. We aimed to investigate IgG titers and specificities in human sera against different ß-glucans with varying structures. METHODS: IgG anti-ß-glucan was measured by enzyme immunoassay in a random sample of 40 sera from healthy adults, with a panel of 8 differently structured glucans. In a subsequent larger series, IgG anti-ß-(1,6)-glucan was measured in a random sample of 667 sera from three occupational populations with different organic dust exposures. Possible determinants of IgG anti-ß-(1,6)-glucan titers were explored with linear-regression analysis. RESULTS: We found wide variation in anti-ß-glucan IgG levels. The highest titers were found for pure ß-(1,6)-glucan pustulan. Moderate to strong reactions with other ß-(1,6)-containing structures appeared to be due to cross-reacting anti-ß-(1,6)-glucan antibodies. Surprisingly, the mean IgG anti-ß-(1,6)-glucan titer was significantly lower in agricultural workers - with highest organic dust exposure - than in spray painters and bakery workers. Smoking status was associated with lower IgG anti-ß-(1,6)-glucan titers in all populations. CONCLUSIONS: IgG to ß-(1,3)- and ß-(1,6)-glucans can be found in normal human sera. ß-(1,6)-glucans appear to be much more potent antigens. The health impact of high anti-ß-(1,6)-glucan antibody levels remains unclear and further investigations are needed.