Human neutrophils are devoid of the integral membrane protein caveolin

The secretory vesicles of human neutro- phils are rapidly mobilizable vesicles that contain several GPI-linked proteins, a characteristic fea- ture of caveolae in other cells. To investigate whether secretory vesicles are structurally related to caveolae, we examined human neutrophils for the presence of caveolin, a major constituent of caveolae, by immunoblotting using monoclonal and polyclonal antibodies. Caveolin was not detected in lysates of human neutrophils nor in isolated plasma membrane/light membrane fractions in which secre- tory vesicles localize. In contrast, caveolin was readily detected in isolated membranes of adipose cells. We conclude that human neutrophils are devoid of caveolin and that secretory vesicles are not related to caveolae nor dependent on caveolae for mobilization. J. Leukoc. Biol. 63: 563-566; 1998.