Soluble and immobilized anti-Ig antibodies in the regulation of LPS-induced lymphoblasts.

Anti-immunoglobulin (anti-Ig) causes suppression of secretion of immunoglobulin by LPS-activated pig B lymphoblasts. The cellular level at which anti-Ig influences immunoglobulin secretion has been investigated, using soluble anti-Ig which enters B cells, and anti-Ig immobilized onto acrylamide bead or plastic surfaces which can act only at the B-cell surface. Suppression of secretion only occurred with soluble anti-Ig, indicating that the intracellular processing of antibody after its complexing on the cell surface was necessary for suppression to occur. Immobilized anti-Ig acted as effectively as soluble antibody in activation of resting B cells into mitosis, showing that the activating signal of anti-Ig is received at the cell surface. Electron microscopy has shown that the block to secretion after soluble anti-Ig resulted from the accumulation of smooth membrane-bounded intracellular vesicles which, by immunofluorescence, contained immunoglobulin. The formation of vesicles was intimately associated with the intracellular localization of 125I-labelled anti-Ig which was used to follow cellular processing of anti-Ig.