Probing the mechanisms of low immunogenicity of a lipocalin allergen, Bos d 2, in a XXXX model.

@entity2047 @entity19 @entity10713 @entity1618 @entity58 @entity22139 @entity116 @entity291
BACKGROUND: Bos d 2, a major @entity291 allergen of the lipocalin family, stimulates very weakly @entity291 dust-asthmatic subjects' peripheral blood mononuclear cells and the spleen cells of several inbred @entity19 strains immunized with the allergen. OBJECTIVE: To identify the immune mechanisms accounting for the weak stimulatory capacity of Bos d 2. METHODS: The spleen cell responses of BALB/c @entity19 immunized with the allergen and with hen egg lysozyme and @entity116 toxoid as control antigens were examined using several in vitro methods. RESULTS: Analysis of the numbers of spleen cells in the antigen-stimulated in vitro cultures with the vital dye @entity10713 showed that Bos d 2 induced a smaller expansion of cells in comparison with the control antigens. Increased cell death in vitro did not account for the weak response against Bos d 2. The number of spleen cells reacting against Bos d 2 also proved to be the lowest when they were analysed by labelling the stimulated cells with @entity22139 or by enumerating cytokine-secreting cells by ELISPOT. Eliminating CD8+ cells in the in vitro culture did not enhance the response against Bos d 2. Bos d 2 was also the weakest of the antigens to stimulate the production of soluble cytokines. Adding @entity2047 , @entity58 or antibody against TGF-beta in the antigen-stimulated spleen cell cultures enhanced the proliferative responses against all the antigens, whereas adding IL-12 or antibody against @entity58 or @entity1618 did not enhance the responses. CONCLUSION: The results exclude several mechanisms of peripheral tolerance as an explanation for the poor immune response against Bos d 2, and suggest that the allergen is recognized by a low number of specific T cells. The weak immunogenicity of Bos d 2 may be related to its allergenicity.
