PTK2B and systemic lupus erythematosus: Quantitative analysis shows PYK2 in PBMCs from SLE, but not RA patients (0.96 ± 0.34 in RA), was significantly up-regulated (1.13 ± 0.35 and 1.28 ± 0.30) in inactive and active SLE patients, respectively, compared with that from healthy donors (0.94 ± 0.41).