The defense mechanisms operate through humoral immune proteins, which include pattern recognition proteins (PRPs) as well as antimicrobial peptides (AMPs) and multiple other immune molecules. The proteins play three vital roles in immune detection of pathogens while enabling immune system activation and microbial threat elimination. PRPs operate as fundamental components of the humoral system by identifying pathogen-associated molecular patterns (PAMPs) on microbial surfaces. The detection process activates immune responses that produce AMPs together with reactive oxygen species (ROS) and additional immune molecules, which eliminate pathogens. Different invertebrate species, including shrimp and crayfish, along with mollusks, together with insects, will be examined in this section regarding their humoral immune proteins’ roles. The study includes an evaluation of pattern recognition proteins PGBP and PGRP, along with BGBP and BGRP, and Toll receptors throughout invertebrate phyla, along with their activation methods (Table 3.1).