<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:An investigator studying immune response administers a 0.5 mL intradermal injection of an autoclaved microorganism to a study volunteer. Four weeks later, there is a 12-mm, indurated, hypopigmented patch over the site of injection. Which of the following is the most likely explanation for the observed skin finding?? A: Increased lipid uptake by macrophages, B: Increased antibody production by B cells, C: Increased activity of neutrophils, D: Increased activity of CD4 Th1 cells, E: Increased release of transforming growth factor beta,  <response>: This is a question about delayed type hypersensitivity DTH reaction. The description of an indurated, hypopigmented patch at the site of injection 4 weeks after exposure to an antigen is classic for a DTH reaction mediated by T cells.Choice A about lipid uptake by macrophages is incorrect because DTH is mediated by T cells, not macrophages. Choice B about B cell antibody production is incorrect because DTH reactions are mediated by T cells, not antibodies from B cells.Choice C about neutrophils is incorrect because neutrophils are involved in acute inflammatory reactions, not delayed reactions like DTH. Choice D about CD4 Th1 cells is correct because DTH is mediated by Th1 cells secreting cytokines like IFN-gamma. The induration and delayed timeline are consistent with a Th1 cell mediated process.Choice E about TGF-beta is incorrect because TGF-beta suppresses immune responses and DTH is due to an exaggerated cell-mediated immune response.D: Increased activity of CD4 Th1 cells 