Development and Function of Innate Response Activator B Cells (image) Massachusetts General Hospital Share Print E-Mail Caption The precursors of IRA-B cells, B1a B cells, reside in the peritoneal cavity. When B1a cells recognize bacteria infecting the peritoneal cavity, they migrate out of the peritoneal cavity, accumulate in the red pulp of the spleen or the bone marrow, and become IRA-B cells that secrete abundant amounts of GM-CSF. This growth factor acts on cells expressing its receptor, arming the innate immune response for efficient bacterial clearance. Credit Filip Swirski, Ph.D., MGH Center for Systems Biology Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.