This is a randomized, double-blind, placebo-controlled, single-dose, dose escalation study in healthy male and or female subjects and subjects with Rheumatoid Arthritis (RA) to determine the safety and tolerability of MORAb-022.

Inclusion Criteria for Rheumatoid Arthritis (RA) Subjects:

• Male or female subjects age greater than or equal to 18 years and less than or equal to 75 years.
• Subjects with RA diagnosis per the 2010 Rheumatoid Arthritis Classification Criteria per American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR.)
• BMI less than or equal to 35 kg/m2 at Screening.
• Active RA characterized by DAS28 score of less than or equal to 5.1 at Screening.
• Have been stabilized on their current dose (up to 25 mg/week) of methotrexate(MTX) for at least 4 weeks before randomization.

Exclusion Criteria for Rheumatoid Arthritis (RA)Subjects:

• Subjects with severe active RA and are not on a stable therapeutic regimen at Screening.
• Subjects without significant articular RA.
• Relevant history of significant respiratory disease (e.g., chronic bronchitis, asthma in last 5 years, chronic obstructive pulmonary disease, tuberculosis, interstitial lung disease, such as pneumonitis and pulmonary alveolar proteinosis, as well as significant inhalation exposure to silicon and other substances) that required treatment and/or follow up under the direction of a physician.
• Presence of GM-CSF autoantibodies above normal at Screening.
• Abnormal chest x-ray or PFTs as judged by the investigator at Screening as clinically significant.
• Positive Quantiferon test.
• History of clinically relevant hypersensitivity reactions (e.g., to gold therapy)
• History of medication use that might have carryover effects during the study.
• Previous administration of a GM-CSF modulator within 6 months of randomization, or previous administration of a monoclonal antibody or immunoglobulin fusion protein that is not (or worded as "other than") a GM-CSF modulator within 3 months of randomization.
• Use of any biological therapy other than the test article during the study (informed consent to termination visit)
• Subjects who consume greater than 14 alcoholic drinks per week for males or 7 alcoholic drinks per week for females.
• Weight greater than 120 kg at Screening.
• Use of parenteral and/or intra-articular steroids, immunosuppressants, investigational drugs, and oral anticoagulant drugs within 4 weeks prior to randomization. Oral steroid treatment is permitted if the dosage is less than or equal to 10 mg of prednisone daily, is stable for a minimum of 4 weeks before the study and remains unchanged throughout the study.