After CD40L co-stimulation, Syk(Y352) phosphorylation in RA and pSS CD27+ memory B cells and in SLE CD27− B cells was comparable to HD (Figure 4B), whereas BCR engagement alone gave rise to diminished pSyk(Y352) (Figures 2B, 4B). Here, CD40LG is linked to systemic lupus erythematosus.