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. Author manuscript; available in PMC: 2013 Dec 28.
Published in final edited form as: Science. 2013 May 16;340(6140):1587–1590. doi: 10.1126/science.1237572

Fig. 3.

Fig. 3

B cell antigen extraction requires myosin IIa contractility and clathrin-mediated endocytosis. (A) Antigen internalization (anti-Igμ) and (B) number of invaginations pulled from PMS by Ramos B cells expressing shRNA against AP2, dynamin2, Rock1, or myosin IIA. (C) Antigen internalization (anti-Igκ) from PMS (left y-axis) or solution (right y-axis) by primary B cells treated with inhibitors against dynamin2 (dynasore), Rock1 (Y-23632), or myosin IIA (blebbistatin). (D) Number of invaginations pulled from PMS by primary B cells treated with inhibitors. A-D, means±SEM, n=17-25 cells for internalization from PMS, n=7-15 cells for invagination numbers, n=3 experiments for soluble antigen internalization. *, p<0.01, **, p<0.05 in non-parametric tests against controls. F.u., fluorescence units. (E) Top, TIRF image of a primary B cell expressing myosin IIa regulatory light chain (RLC)-GFP (Myo) spread on DiD-labeled PMS loaded with antigen. Yellow squares show a region magnified below. Closed arrowheads show invagination, open arrowheads show myosin IIa structures. Scalebar, 1 μm. (F) Quantification of myosin IIa RLC fluorescence in invaginations grouped by lifetime (mean±SEM, n=15 cells). *, p<0.01 in paired t-tests.