Direct demonstration of membrane IL-1 alpha on the surface of circulating B lymphocytes and monocytes

A mAb against IL-1 alpha has been used in a high sensitivity immunofluorescence procedure to demonstrate directly the presence of surface IL-1 alpha on human monocytes and B cells from blood and tonsil. IL-1 alpha could be detected on monocytes and a subset (around 30%) of B cells without any in vitro activation. Although the subset of B cells expressing IL-1 alpha was distinct (i.e., the distribution of fluorescence intensity was bimodal), no correlation was seen with any other B cell subset marker in blood. In tonsil, IL-1 alpha was expressed by cells with a phenotype that suggested that they represented a subset of mantle zone B cells. Activation of tonsil B cells with anti-IgM, IL-4, IL-2, and mixtures of these reagents led to small increases in IL-1 alpha expression, as did activation of unfractionated tonsil cells with PHA.