Description: The SB/199 monoclonal antibody reacts with mouse CD127, the high affinity a subunit of the mouse IL-7 receptor. IL-7 receptor a chain is expressed by immature B cells in the bone marrow, double-negative (CD4-/CD8-), single-positive (CD4+ and CD8+), but not double-positive (CD4+/CD8+) thymocytes. In the periphery, mature T cells express low levels of CD127. Binding of SB/199 blocks the binding of A7R34, another antibody which recognizes mouse CD127.