CD19 and rheumatoid arthritis: Noteworthy, RA-related phosphoprotein profile changes are unique to the CD19+CD27−IgD+IgMlow/− subset of autoreactive BND cells: nominal logistic fit demonstrated that RA predictive value of the combined phosphorylation profile of several major BCR signaling proteins and Ca2+ levels in response to BCR stimulation [2] in BND cells was highly significant (R2 = 1.0, p = 0.0002), while in mature naïve CD19+IgM+ B cells this predictive value was substantially less evident (R2 = 0.505, p = 0.053).