Early Markers of Disease and Response to Therapy

Abatacept will be administered by subcutaneous injections weekly for 3 months. Dosing is according to body weight at screening visit and will be administered as follows: up to 25 kg receive 50 mg (0.4 mL); 25 to \<50 kg receive 87.5 mg (0.7 mL), and \> 50 kg receive 125 mg (1.0 mL) per dose.