SummaryWhereas T lymphocyte (T cell) activation is the key event in the acquisition of skin sensitization and subsequent elicitation of allergic contact dermatitis, the humoral component of immune responses to organic contact allergens has received little consideration. There is evidence that, in experimental animals, topical exposure to potent contact allergens is associated with B cell activation and proliferation, and hapten-specific antibody production. However, there is very limited evidence available for anti-hapten antibody responses being induced following topical exposure of humans to contact allergens. Nevertheless, it is important to appreciate that there are almost no negative studies in which evidence for antibody production as the result of skin sensitization has been sought and not found. That is, there is absence of evidence rather than evidence of absence. Furthermore, exposure to chemical respiratory allergens, in which the skin has been implicated as a potential route of sensitization, results in anti-hapten antibody responses. It is proposed that skin sensitization to contact allergens will normally be accompanied by antibody production. The phenomenon is worthy of investigation, as anti-hapten antibodies could potentially influence and/or regulate the induction of skin sensitization. Moreover, such antibodies may provide an informative correlate of the extent to which sensitization has been acquired.Key words: allergic contact dermatitis; antibody response; B cell; hapten; IgG; IgM; skin sensitization.From an immunological perspective, the acquisition of skin sensitization and the elicitation of allergic contact dermatitis are immune and inflammatory responses mediated by antigen (hapten)-specific T cells (1-3). For this reason, it is the activation, differentiation and regulation of T cells upon which attention has been focused, and there are available excellent recent reviews that describe
Accepted for publication 21 September 2015the roles played by T cells in skin sensitization and allergic contact dermatitis (4-7).However, at least in animals, contact allergens provoke both humoral and cell-mediated immune responses. Thus, topical encounter with a contact allergen will induce anti-hapten antibody formation in addition to the activation and expansion of responsive T cells (8-10). Given the predominant role played by T cells in skin sensitization, it is perhaps not surprising that anti-hapten antibody responses have received comparatively little attention. This is unfortunate because, in theory, a hapten-specific antibody has the ability to influence both the acquisition of skin sensitization and the subsequent elicitation of allergic reactions. Moreover, it is possible that the vigour and isotype distribution of anti-hapten antibodies induced by exposure to contact allergens