Cutting edge: Dichotomy of homing receptor dependence by mucosal effector B cells: alpha(E) versus L-selectin

The common mucosal immune system may be compartmentalized because lymphocyt e homing to the upper respiratory tract appears to be mediated by L-selecti n interactions rather than alpha (4)beta (7) interactions, as is the case f or gut-associated lymphoreticular tissue. To assess the role of L-selectin in effector B cell immunity, L-selectin-deficient mice were intranasally im munized with cholera toxin (CT), and mucosal immune responses were compared with C57BL/6 mice. The absence of L-selectin correlated with a reduction i n CT-specific secretory-IgA responses in nasal passages and reproductive tr act, but not intestinal lamina propria. Cell sorting experiments showed tha t an L-selectin-dependent subset was responsible for CT-specific responses in nasal passages and reproductive tract, whereas an alpha (E)beta (+)(7) B cell subset was responsible for L-selectin-independent intestinal immunity . This study provides evidence for compartmentalization of the common mucos al immune system into "intestinal" vs "nonintestinal" effector sites.