No abstract

Although allergen-specific CD41 T cells are detectable in the peripheral blood of both individuals with or without allergy, their frequencies and phenotypes within the memory as well as naïve repertoires are incompletely known. Here, we analyzed the DRB1*0401-restricted responses of peripheral blood-derived memory (CD4 ) T cells from subjects with or without allergy against the immunodominant epitope of the major cow dander allergen Bos d 2 by HLA class II tetramers in vitro. The frequency of Bos d 2 127-142 -specific memory T cells in the peripheral blood-derived cultures appeared to be higher in subjects with allergy than those without, whereas naïve Bos d 2 127-142 -specific T cells were detectable in the cultures of both groups at nearly the same frequency. Surprisingly, the TCR avidity of Bos d 2 127-142 -specific T cells of naïve origin, as assessed by the intensity of HLA class II tetramer staining, was found to be higher in individuals with allergy. Upon restimulation, long-term Bos d 2 127-142 -specific T-cell lines generated from both memory and naïve T-cell pools from individuals with allergy proliferated more strongly, produced more IL-4 and IL-10, and expressed higher levels of CD25 but lower levels of CXCR3 than the T-cell lines from individuals without allergy, demonstrating differences also at the functional level. Collectively, our current results suggest that not only the memory but also the naïve allergen-specific T-cell repertoires differ between individuals with or without allergy. Allergen-specific CD4 1 T cells are present at very low frequencies in the peripheral blood of both subjects with or without allergy. This phenomenon has hampered detailed studies of human allergen-specific T-cell responses, since commonly used techniques, such as the measurement of proliferation or cytokine production, are relatively insensitive and usually require extensive in vitro culture to expand T cells for analyses. Moreover, these techniques do not allow a clear discrimination between antigen-specific T cells and nonspecific T cells induced by bystander activation. Therefore, it is not surprising that previous studies measuring the proliferative responses or cytokine production of PBMC or T-cell lines (TCL) upon stimulation with allergens or allergen peptides have failed to demonstrate a consistent difference between subjects with allergy and those without [3][4][5][6][7]. The current situation has been significantly improved through the development of HLA class II tetramer technology, which allows the direct visualization of rare antigenspecific T cells by flow cytometry [8]. In recent years, HLA class II tetramers have successfully been used to detect CD4 1 T cells specific to allergen epitopes in both healthy subjects and those with allergy [9][10][11][12][13].Most of the previous research on human antigen-specific CD4 1 T-cell responses has been performed using PBMC or purified peripheral blood CD4 1 T cells. It is important to note, however, that the peripheral blood CD4 1 T-cell repertoire in humans...

No abstract

Most mammal-derived respiratory allergens belong to the lipocalin family of proteins. Determinants of their allergenic capacity are still unknown. Innate immune cells, in particular dendritic cells, have been shown to be involved in the allergenicity of some proteins. As recognition by dendritic cells is one of the few plausible mechanisms for the allergenicity of proteins, we wanted to investigate their role in the allergenicity of lipocalin allergens. Therefore, we first incubated human monocyte-derived dendritic cells with immunologically functional recombinant allergens mouse Mus m 1, dog Can f 1 and 2, cow Bos d 2, horse Equ c 1 and natural Bos d 2. Then, the surface marker expression and cytokine production of dendritic cells and their capacity to promote T cell proliferation and Th2 immune deviation in na€ ıve CD4 + T cells were examined in vitro. We found that near to endotoxin-free lipocalin allergens had no effect on the activation, allostimulatory capacity or cytokine production of dendritic cells. The dendritic cells could not induce immune deviation in na€ ıve CD4 + T cells. In contrast, lipopolysaccharide activated the dendritic cells efficiently. However, lipocalin allergens were not able to modify the lipopolysaccharide-induced responses. We conclude that an important group of mammal-derived respiratory allergens, lipocalins, appear not to be able to activate dendritic cells, a major component involved in the allergenicity of some proteins. It is conceivable that this incapacity of lipocalin allergens to arouse innate immunity may be associated with their poor capacity to induce a strong T cell response, verified in several studies.