Guard theory is a branch of immunology which concerns the innate sensing of stereotypical consequences of a virulence factor or pathogen.[1] This is in contrast to the classical understanding of recognition by the innate immune system, which involves recognition of distinct microbial structures- pathogen-associated molecular patterns (PAMPs)- with pattern recognition receptors (PRRs). Some of these stereotypical consequences of virulence factors and pathogens may include altered endosomal trafficking and changes in the cytoskeleton.[2] These recognition mechanisms would work to complement classical pattern recognition mechanisms.[3][4]