Study to assess the ability of healthy subjects to build anitbodies to tetanus and pneumococcal vaccines after receiving a single intravenous dose of Abatacept, a drug which is being developed for the treatment of Rheumatoid Arthritis and which can affect the immune system.

Inclusion Criteria:

• Healthy Subjects
• Body Weight between 60 and 100 kg.
• Males and Females must be using adequate contraceptive methods during study and for 10 weeks after dose of study mediciation.

Exclusion Criteria:

• Females who are prgnant or breastfeeding
• History of autoimmune disorder, immunodeficiency, or infection within past 3 months.
• Active TB requiring treatment within the previous 3 years.
• Positive breast cancer screen, PPD test.
• Vaccination with tetanus or pneumococcal vaccine within 5 years.
• Vaccination with any live vaccine within 4 weeks.
• History of drug or alcohol abuse.
• Any significant allergy.