Marginal zone and B1B cells unite in the early response against T-independent blood-borne particulate antigens

The rate of pathogen elimination determines the extent and consequences of an infection. In this context, the spleen with its highly specialized lymph oid compartments plays a central role in clearing blood-borne pathogens. Sp lenic marginal zone B cells (MZ), by virtue of their preactivated state and topographical location, join B1 B cells to generate a massive wave of IgM producing plasmablasts in the initial 3 days of a primary response to parti culate bacterial antigens. Because of the intensity and rapidity of this re sponse, combined with the types of antibodies produced, splenic MZ and B1 B cells endowed with a "natural memory" provide a bridge between the very ea rly innate and the later appearing adaptive immune response.