CD38 and neoplasm: The level of cytokine production, including interferon γ (IFN‐γ), interleukin‐2 (IL‐2), tumor necrosis factor α (TNF‐α), and GM‐CSF, appeared to correlate with the level of CD38 expression in the tumor cells, i.e., Raji, Daudi, RPMI8226, and THP1 cells stimulated more cytokine production than K562 cells (Figure 3 and Figure S4, Supporting Information).