Several lipocalins exhibited IgE cross-reactivity, probably due to the sequential identity of the proteins and also due to similarities in their three-dimensional structures. The clinical significance of the findings needs to be elucidated. Low-level IgE cross-reactivity can play a role in regulating immune response to lipocalin allergens.

The recombinant allergens can be used reliably to identify Can f 1 and Can f 2-sensitized individuals. However, the two allergens are insufficient as reagents for diagnosing dog allergy.

One prerequisite for developing peptide-based allergen immunotherapy is knowing the T cell epitopes of an allergen. In this study, human T cell reactivity against the major dog allergen Can f 1 was investigated to determine peptides suitable for immunotherapy. Seven T cell epitope regions (A–G) were found in Can f 1 with specific T cell lines and clones. The localization of the epitope regions shows similarities with those of the epitopes found in Bos d 2 and Rat n 1. On average, individuals recognized three epitopes in Can f 1. Our results suggest that seven 16-mer peptides (p15–30, p33–48, p49–64, p73–88, p107–122, p123–138, and p141–156), each from one of the epitope regions, show widespread T cell reactivity in the population studied, and they bind efficiently to seven HLA-DRB1 molecules (DRB1*0101, DRB1*0301, DRB1*0401, DRB1*0701, DRB1*1101, DRB1*1301, and DRB1*1501) predominant in Caucasian populations. Therefore, these peptides are potential candidates for immunotherapy of dog allergy.

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...

The immunological characteristics of an important group of animal-derived allergens, lipocalins, are poorly known. To explore the immunology of the lipocalin allergen Bos d 2, several mouse strains with different H-2 haplotypes were immunized with the allergen. Only the BALB/c mouse mounted a distinct humoral response against Bos d 2. The proliferative spleen cell responses of all mouse strains remained very weak. Further experiments with BALB/c mice confirmed that Bos d 2 is a weak inducer of both humoral and cellular responses, and that the responses were weaker than with the control antigens hen egg lysozyme (HEL) and tetanus toxoid. IgG subclass analyses showed that Bos d 2 was prone to favor the T(h)2 response. Although s.c. immunization using complete Freund's adjuvant favored the T(h)1-deviated immune response by lymph node cells, Bos d 2 was able to induce the production of IL-4 while the control antigen HEL did not. Epitope mapping revealed that BALB/c mice recognized one immunodominant epitope in Bos d 2, almost identical to that recognized by humans. The epitope was shown to be immunogenic in subsequent experiments. However, further studies are needed to clarify the significance of priming and stimulation doses of the immunodominant and other epitopes in Bos d 2 for the outcome of immune response against the allergen. The murine immune response against Bos d 2 closely resembled that observed in humans. The weak immunogenicity of Bos d 2 may be associated with its allergenicity.