Cell surface changes in capping studied by correlated fluorescence and scanning electron microscopy.

: A simple method has been devised for correlating fluorescence microscopy and scanning electron microscopy, whereby the identical cell observed by the former can be observed by the latter. With this methodology, we have studied the sequence of cell surface changes which occur when mouse B lymphocytes, bearing immunoglobulin (Ig) on their surfaces, interact with fluoresceinated anti-Ig antibodies. Initially, the pattern of staining is diffuse; then, rapidly, patching occurs, followed by the sweeping of the patches into a cap. Accompanying these events are: the disappearance of microvilli, the formation of ruffles and lamellipodia at the pole of the cell opposite the capped pole, the presence of a constriction ring beneath the cap, ameboid shapes, and the translocation of the cell in a direction opposite the cap. Whereas the cell body is smooth, the capped pole frequently shows the presence of numerous microvilli. However, not all capping cells show the changes, and cells capped in the presence of cytochalasin B usually show none of them, except that their surfaces are smooth. Furthermore, T-cells undergoing translocation show the same cell surface changes as do B-cells. Whereas the contractile apparatus of the cell is considered to underlie all these phenomena, it is concluded that the cell surface changes do not result from patching and capping per se, but rather are an expression of the cell translocation also induced by the anti-Ig antibody.