Fig. 1From: Was the evolutionary road towards adaptive immunity paved with endothelium?The vascular system plays a critical role in supporting the AIS. The lower blood volume of vertebrates allows for a higher concentration of antibodies thus facilitating binding kinetics and ultimately rendering antibodies cost-effective. Similarly, the endothelium controls local permeability of vasculature as well as the transcellular trafficking of immunoglobulins, thus facilitating a local increase in antibody concentrations. Moreover, endothelium cells promote directional blood flow and facilitate cell migration of B- and T-cells, thus exposing these cells to more epitopes which promote the efficacy of the AISBack to article page