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Updated: Aug 11, 2026

Visualizing the Actin and Microtubule Cytoskeletons at the B-cell Immune Synapse Using Stimulated Emission Depletion (STED) Microscopy
Published on: April 9, 2018
Membrane immunoglobulin-cytoskeletal interactions--II. Biochemical analysis of cytoskeletally associated IgM
1Graduate Program in Biochemistry, Dartmouth Medical School, Hanover, NH 03756.
Abstract:
In a previous paper [Albrecht and Noelle, J. Immun. 141, 3915 (1988)], biochemical and flow cytofluorometric analysis revealed a 78,000 mol. wt cell surface protein that was constitutively associated with the detergent-insoluble fraction (cytoskeleton) of B lymphocytes. The identity of this band was serologically confirmed as IgM and was therefore referred to as cyto-IgM. Since cyto-IgM may play an integral role in mIgM-cytoskeletal interactions, the molecular nature of cyto-IgM was investigated. In its non-reduced form, cyto-IgM was pentameric. Treatment with endoglycosidase F revealed an Ig heavy chain with a mol. wt of 66,000, which was identical to secreted IgM. The cell surface location of cyto-IgM was independently verified by its sensitivity to protease digestion in intact cells. Conditions which eluted cytophilic Ig from the cell surface did not displace cyto-IgM. Cyto-IgM was present in resting B lymphocytes but absent in neonatal cells. The function of cyto-IgM is discussed in the light of these results.
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