FC analysis of MP and IC containing samples. (A) MPs from RA SF and OA plasma have been stained with AX-FITC or CD41a-FITC and were subjected to detergent lysis by 0.05% Triton X-100. moIgG denotes antimouse IgG used for isotype control. (B) SFs from OA and RA patients were stained with anti-IgG-FITC or anti-IgM-FITC and were also subjected to detergent lysis by 0.05% Triton X-100. All plots represent events from the MP gate. (C) To prove MP lysis, isolated MPs were visualized by TEM before and after lysis. Original magnification × 20 000. Scale bars indicate 400 nm. Images were captured at room temperature using Hitachi 7100 electron microscope equipped with a Megaview II digital camera. (D) DLS of MPs before and after addition of detergent. The x-axis is set to logarithmic scale; a(r_h) denotes the coefficient of autocorrelation function of the scattered electric field. Arrow indicates the remaining MP-related signal. Arrowhead indicates the signal of Triton X-100. DLS experiments were carried out at 21°C. (E) Dot plots of RA SFs stained with AX-PE and anti-IgG-FITC or anti-IgM-FITC (n = 3 in each group). Events are shown within the R1 gate. (F) IgG⁺, IgM⁺, total, and AX⁺ event counts within the MP of RA and OA SFs. Horizontal lines indicate mean values. The P values were obtained from Mann-Whitney test (n = 21).