This is an exploratory study to develop methodologies for the assessment of T-cell mediated therapies via skin immune challenges studies in healthy volunteers. The study will investigate what is the most appropriate; skin challenge agent, time and methodology to sample and characterise T-cells in the delayed type hypersensitivity (DTH) skin reaction. The skin challenge agents to be used in this study will be the neoantigen Keyhole Limpet Hemocyanin (KLH) and recall antigen Tuberculin Purified Protein Derivative (PPD). Part A of the study will assess an intradermal (ID) KLH challenge in three subjects to assess if the immune response to KLH is initiated by the innate or adaptive immune system. Each subject will receive one ID dose of 0.1 milligram (mg) KLH and will be assessed for a skin inflammatory response. Part B of the study will assess repeat ID challenges 28 days apart; the objective will be to characterise the T-cell response to each challenge and the kinetics of that response.