Armies of white blood cells patrol our bloodstream defending us against a multitude of infections. When one of their ranks – in this case a B cell – encounters an invasive pathogen [viruses or bacteria], it raises the defence with a specialised protein armory. These antibodies are lying on wait around the perimeter of the B cell. Triggered by specific proteins on the surface of invaders, the B cell mobilises other antibody proteins within to join in the attack. Their journey to the surface of the cell is facilitated by a network of motor-like actin proteins. This mouse B cell (perimeter drawn in white) shows how actin strands (stained yellow-green) attach to the cell membrane (at arrowheads), which guides the antibodies to their destination. Then these proteins can get on with the job of neutralising and ousting the invader.
Written by Alice Lighton
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences (the new name for the MRC Clinical Sciences Centre) the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.