CD4 and Dravet syndrome: Peripheral T-cell homeostatic proliferation compensates for the thymic involution-related decrease in T-cell production in 22q11.2 DS patients [30]. As thymic production is limited, the only available avenue is the proliferation of existing T cells, expressed by conversion of the naive surface phenotype (CD4+CD45RA+) to the memory phenotype (CD4+CD45RO+) [30].