Identifcation of Human B1 cells

The mission of B lymphocytes is considered to reside primarily in immunoglobulin production; however, the success of B cell depletion in autoimmune diseases previously thought to be T cell-mediated suggests that some B cells fulfill other roles in autoimmunity. We examined the recently identified human B1 cell population for T cell stimulatory activity. We found two kinds of B1 cells that are distinguished by multiple surface markers and distinct transcriptomic profiles. In both umbilical cord and adult peripheral blood, the larger of the two, which is CD11b-, constitutes about 90% of B1 cells, whereas the smaller of the two, which is CD11b+, constitutes about 10% of B1 cells. These B1 cell populations differ functionally. CD11b- B1 cells spontaneously secrete much more IgM than CD11b+ B1 cells. In contrast, CD11b+ B1 cells express more CD86, and efficiently stimulate more T cell expansion, than CD11b- B1 cells. These CD11b+ B1 cells are markedly elevated in lupus patients and express increased CD86 and increased T cell stimulating activity in disease. This work distinguishes a novel, T cell-interacting B1 cell population whose expression and activity may be a reflection of, and a therapeutic target in, autoimmune disease. abstract Four groups each group comprising 3 samples for a total of 12 samples of human B cells were analyzed