Text S1 - A Case Of Convergence: Why Did a Simple Alternative to Canonical Antibodies Arise in Sharks and Camels?

Section 1: The rationale for the H2L2 antibody-based adaptive humoral immune system in jawed vertebrates. Section 2: Absence of CH1 domain in H chains for HCAbs. Section 3: Generation of a large V domain repertoire in absence of the VH-VL combinatorial diversification. Section 4: Producing soluble V domains in absence of VL partner. Section 5: Unique antigen recognition by V-NAR and VHH. (RTF)