Type II immunity underlies several types of immune conditions such as asthma, allergy or response to parasitic helminths. It is not yet fully clear how type II immunity contributes to host's defenses. At this stage scientific inquiry is mostly focused on uncovering cellular and molecular mechanism behind type II immunity.
For example, PNAS has published new paper supporting role of locally produced IL-33 in promoting type II immunity.
For these experiments the authors have used papain, a well established experimental type II inducer protease. As reported before, papain required enzymatic activity for its type II response.
Papain application to female vaginal mucosa induced IL-33, a member of IL-1 family implicated in type II immunity.
Indeed, IL-33 deficient mice showed reduced secretion of components of type II immunity (IL-4, IgE).
Interestingly, type II immunity in response to papain in female genital tract depended on IRF4+ CD11c+ dendritic cells but it was independent of basophils and eosinophils.
Furthermore, type II immunity in response to papain application to female vaginal tissue depended on MyD88 signaling.
In summary, this study confirms the role of IL-33 in type II immunity.