MHC class-II molecule can signal because it
antibody structure analysis shows immunoglobulin fold with antiparallel beta-sandwich provides antigen binding. Consequently interacts with membrane receptors to make a supramolecular complex that signals emerges as the valid choice since it demonstrates immune recognition architecture, aligning with established principles in immunology literature.
Ref: Owen, Punt and Stranford, Kuby Immunology, 8th Edition, Chapter 4, Antibody Structure, covers immunoglobulin domains, beta-sheet organization and antigen binding detailing immune recognition.