Hematopoietic progenitor cells are innate Th2 cytokine-producing cells.

Typically, hematopoietic stem/progenitor cells (HSPCs) reside within the bone marrow (BM) where they give rise to all hematopoietic populations. However, HSPCs also constantly egress from the BM into the blood and circulate through the peripheral tissues where upon encounter with inflammatory stimuli and epithelial cell-derived cytokines they rapidly release very high levels of Th2 cytokines/chemokines and differentiate into Th2 effector cells. The novel concept of the dual function of HSPCs as hematopoietic precursors and potent Th2 cytokine producers has important clinical implications in various inflammatory conditions, including allergic diseases.