Memory CD8+ T cells generated in response to a natural infection can be stimulated by cells other than dendritic cells and depending on subset they can act immediately once they see their antigen displayed on MHC class I. If they belong to the tissue resident memory CD8+ T cell subset they may not even proliferate, which raises the question if screening for increases in circulating T cells is adequate to predict immune-mediated rejection of AAV-transduced cells. Here, CD8A is linked to infection.