BCR and rheumatoid arthritis: As B cells from RA patients are known to exhibit hyper BCR signaling (Nakken et al., 2011b; Oligino and Dalrymple, 2003; Szodoray et al., 2006), it is our speculation that the enhanced activation of RA patient B cells on soft substrates results from signaling-dependent accumulation of BCRs into the BCR microclusters, as discussed above.