C-type lectins are a diverse superfamily of mainly Ca-dependent proteins that bind a variety of carbohydrates (including the glycan skeleton of peptidoglycan), and function as innate immune receptors. CLR proteins that bind to peptidoglycan include MBL (mannose binding lectin), ficolins, Reg3A (regeneration gene family protein 3A) and PTCLec1. In mammals, they initiate the lectin-pathway of the complement cascade.