This single-center, randomized, placebo-controlled, double-blind, multiple ascending dose study will evaluate the safety, pharmacokinetics and immunogenicity of MCAF5352A in healthy volunteers. Subjects will be randomized to receive either MCAF5352A or placebo on Days 1, 15 and 29.

Inclusion Criteria:

• Healthy males and females, 18 - 55 years of age
• Subjects in good health as determined by screening medical history, physical examination, vital signs, 12-lead ECG and laboratory tests
• Body weight between 45 kg and 110 kg
• Female subjects must be willing to use two effective methods of contraception from screening to a minimum of 4 months after the last dose of study drug

Exclusion Criteria:

• Pregnant or lactating women
• Positive for hepatitis B, hepatitis C or HIV infection
• History of significant chronic or recurrent infections
• History of clinically significant drug allergy and/or a known hypersensitivity to protein therapeutics or formulation components or a related drug
• History of alcohol or drug abuse within 12 months prior to Day 1, or evidence of such abuse
• Subjects who have previously received the study drug
• Participation in a clinical trial within 4 weeks prior to Day 1 or use of any experimental or biologic therapy within 12 weeks prior to Day 1 or within 5 half-lives of the product, whichever is greater