Drugs that disrupt microtubuli do not inhibit lymphocyte activation.

Abstract

LYMPHOCYTE activation by lectins is initiated by the binding of the lectin to a cell surface receptor. It is not known, however, how this event occurring on the cell membrane is converted into a signal that is transmitted to the cell interior. Edelman and coworkers1–4 have advanced the hypothesis that lectin receptor sites may be attached to a submembranous microtubular system in a reversible way. This attachment could then determine the receptor mobility in the plane of the membrane and could also constitute a system for transmembrane signal transmission. The hypothesis is based, to a large extent, on the releasing effect that microtubule-disrupting drugs have on the inhibition of surface immunoglobulin cap formation in mouse B lymphocytes by concanavalin A (con A)2,3. Furthermore, evidence has been presented that colchicine delayed and suppressed the appearance of con A-induced blast cells in human lymphocyte cultures, that there is a delay in the onset of DNA synthesis in cultures containing colchicine and that drug sensitivity decreases with increasing culture time in the presence of con A4. Cap formation of surface immunoglobulin (Ig) is a phenomenon restricted to Ig-bearing B lymphocytes and these cells are not activated by con A. It is felt therefore that observations on this population do not bear directly on the relationship between the con A receptors and microtubuli as a signal-transducing mechanism. The other observations are suggestive but not conclusive for such a role of the microtubular system.