Fig. 6.

Adenosine affects the B cell receptor pathway. In B effector cells, binding of the antigen α-µ-F(ab’)₂ to the BCR induces Syk and PIP3 activation supported by PI3K signaling. PIP3 recruits BTK, inducing auto-phosphorylation. The activated BTK activates PLCγ2 and IP3, binding to the endoplasmatic reticulum (ER), which secrets Ca²⁺. On B_reg cells, extracellular ADO is produced by hydrolysis of ATP by the ectonucleotidases CD39 and CD73. ADO binds to different ADO receptors, downregulating the auto-phosphorylation of BTK and the Ca²⁺ influx in CD73^neg B cells. In B_reg cells, no BTK phosphorylation was found upon binding of the antigen α-µ-F(ab’)₂