Mackall has pioneered cancer immunotherapies for children. Her early research defined the effects of traditional cancer therapies on the immune system, where she identified the role of the thymus in human T cell regeneration and discovered that Interleukin-7 (IL-7) is the main regulator of T cell homeostasis in humans.[1][10] Her group was among the first to demonstrate impressive activity of CD19 chimeric antigen receptor (CAR T cells) therapies for childhood leukemia and also developed a CAR targeting CD22 that was active in this disease.[11]