Both naïve and memory T-cells from drug-naive donors can be stimulated by parent drug and drug haptens. Thus, drug-derived antigens can stimulate naïve T-cells alongside pre-existing memory T-cells through proposed heterologous immunity with an as yet undetermined peptide antigen.
Gibson, A., Faulkner, L., Wood, S., Park, B. K., & Naisbitt, D. J. (2017). Identification of drug- and drug-metabolite immune responses originating from both naive and memory T cells. Journal of Allergy and Clinical Immunology, 140(2), 578-581.e5. https://doi.org/10.1016/j.jaci.2016.11.032