Click on image to view larger version.
Fig. 2. Mechanisms of allergic reactions to milk proteins. Milk proteins are pinocytosed by antigen presenting cells (APC) and peptide epitopes are presented to T cells. Dendritic cells are an important class of APCs with a strong ability to program naive T cells. In IgE-mediated allergy, Th2 effector T cells signal B cells via interleukin-4 (IL-4) to class switch antibody production to allergenic milk protein-specific IgE, which then binds to, and arms, mast cells (sensitization). Milk proteins cross-linking the IgE on armed mast cells cause cell degranulation and rapid release of powerful inflammatory mediators (activation). Non-IgE-mediated mechanisms are poorly understood, but may involve activation of inflammatory cells via interferon-gamma (IFN-
). Oral tolerance is achieved by T cell anergy, or by the action of regulatory T cells (T reg) that suppress the action of effector T cells (Th1 and Th2) via interleukin-10 (IL-10), transforming growth factor-beta (TGF-ß), or cell-to-cell contact.
