B1-like innate B cells are present in adult human organs in homeostasis.

B1-like innate B cells are present in adult human organs in homeostasis, expressing murine B1 markers and secreting IgM.

• Why it matters: Understanding whether B1 cells persist into adulthood is crucial for insights into immune regulation and tissue homeostasis, as their roles in humans remain unclear.
• What they did: The study identified B1-like cells in IgM+ and IgA+ memory compartments across adult human organs using transcriptional profiling, B cell receptor sequencing, and cytokine analysis, revealing their similarity to prenatal and murine B1 cells.
• The result: These B1-like cells may contribute to immune regulation through cytokine secretion and tissue interactions, indicating their widespread presence and potential functional significance in adult human tissues.