CD19 and Dravet syndrome: Some immune alterations in DS are age-dependent: a decrease in absolute numbers of T lymphocytes (CD3+), involving both CD4+ and CD8+ subsets, increased number of activated T cells (CD3+, HLA-DR+), marked decreased numbers of B lymphocytes (CD19+), increase in some subclasses of Ig, and increase in the number of cells with markers of NK activity (41) (Figure 3).