SH2B3 (SH2B Adaptor Protein 3): SH2B3 (SH2B Adaptor Protein 3) is an adaptor protein that negatively regulates cytokine signaling in hematopoietic cells. It plays a key role in maintaining hematopoietic stem cell homeostasis and controlling immune responses. Mutations in SH2B3 are linked to various hematologic disorders, including myeloproliferative neoplasms and autoimmune diseases, highlighting its importance in blood cell development and immune regulation.