The cells that make your blood clots are secretly double agents that also run the immune system's command center in your bone marrow.
Megakaryocytes have always been viewed as simple factories that churn out platelets to stop bleeding. This study reveals that they also express MHC II, a protein that allows them to act as professional antigen-presenting cells. They can actually capture bits of pathogens and show them to T cells to trigger a specific immune response. This means they are responsible for both physical healing and the strategic coordination of the body's defense forces. Recognizing this dual role could change how we treat bone marrow diseases and immune disorders.
MHC II-Expressing Bone Marrow Megakaryocytes Are Noncanonical Antigen Presenting Cells that Activate CD4+ T Cells and Regulate the Hematopoietic Niche
SSRN · 6719152
While professional antigen-presenting cells drive adaptive immunity, atypical cell types can fulfill this role in the bone marrow. Megakaryocytes (MKs) are canonically recognized for platelet production, but recent studies indicate functional heterogeneity and immune potential. We found that ~20% of bone marrow MKs express Major Histocompatibility Complex (MHC) II and co-stimulatory receptors CD80, CD86, and CD40. These MKs process and present antigen to activate T cells in an MHC II-dependent m