Browsing by Author "Kobayashi, Takao"

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    Airway exposure initiates peanut allergy by involving the IL-1 pathway and T follicular helper cells in mice
    (Elsevier, 2018-10) Dolence, Joseph J.; Kobayashi, Takao; Iijima, Koji; Krempski, James; Drake, Li Y.; Dent, Alexander L.; Kita, Hirohito; Microbiology and Immunology, School of Medicine
    BACKGROUND: Little is currently known regarding the immunologic mechanism(s) that initiate peanut allergy. Notably, peanut proteins have been detected in house dust, and their levels correlate with peanut allergy prevalence. OBJECTIVE: This study aimed to develop a new mouse model for peanut allergy and to investigate the immunologic mechanisms involved in peanut allergen sensitization. METHODS: To mimic environmental exposure, naive mice were exposed to peanut flour by inhalation for up to 4 weeks. We then analyzed serum levels of IgE antibody and challenged mice with peanut proteins. Immunological mechanisms involved in sensitization were analyzed using cytokine reporter mice, an adoptive cell transfer model, and gene knockout mice. RESULTS: When exposed to peanut flour by inhalation, both BALB/c and C57BL/6 mice developed peanut allergy, as demonstrated by the presence of peanut-specific IgE antibodies and manifestation of acute anaphylaxis on challenge. A large number of follicular helper T (Tfh) cells were also detected in draining lymph nodes of allergic mice. These cells produced IL-4 and IL-21, and they more robustly promoted peanut-specific IgE production than Th2 cells did. Genetic depletion of Tfh cells decreased IgE antibody levels and protected mice from anaphylaxis, without affecting Th2 cells. Furthermore, peanut flour exposure increased lung levels of IL-1α and IL-1β, and mice deficient in the receptor for these cytokines showed a significant decrease in Tfh cells compared with in wild-type mice. CONCLUSIONS: Tfh cells play a key role in peanut allergy, and the IL-1 pathway is involved in the Tfh response to peanut allergen exposure.
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    Follicular helper T cells mediate IgE antibody response to airborne allergens
    (Elsevier, 2017-01) Kobayashi, Takao; Iijima, Koji; Dent, Alexander L.; Kita, Hirohito; Microbiology and Immunology, School of Medicine
    BACKGROUND: TH2 cells have long been believed to play a pivotal role in allergic immune responses, including IgE antibody production and type 2 cytokine-mediated inflammation and pathology. A new T-cell subset, follicular helper T (TFH) cells, is specialized in supporting B-cell maturation and antibody production. OBJECTIVE: We sought to investigate the roles of TFH cells in allergic immune responses. METHODS: Naive mice were exposed to cytokines or natural allergens through the airways. Development of allergic immune responses was analyzed by collecting draining lymph nodes and sera and by challenging the animals. Cytokine reporter mice and gene-deficient mice were used to dissect the immunologic mechanisms. RESULTS: We observed the development of IL-4-producing TFH cells and TH2 cells in draining lymph nodes after airway exposure to IL-1 family cytokines or natural allergens. TFH and TH2 cells demonstrated unique phenotypes, tissue localization, and cytokine responses. TFH cells supported the sustained production of IgE antibody in vivo in the absence of other T-cell subsets or even when TH2 cell functions were severely compromised. Conversely, conditional deficiency of the master regulator Bcl6 in CD4+ T cells resulted in a marked reduction in TFH cell numbers and IgE antibody levels, but type 2 cytokine responses and eosinophilic inflammation in the airways remained unaffected. CONCLUSION: TFH cells play critical roles in the regulation of IgE antibody production. Allergic immune responses to airborne allergens likely involve 2 distinct subsets of IL-4-producing CD4+ T cells, namely TFH and Th2 cells.