The present invention provides humanized, chimeric and human anti-CD19 antibodies, anti-CD19 antibody fusion proteins, and fragments thereof that bind to a human B cell marker. Such antibodies, fusion proteins and fragments thereof are useful for the treatment and diagnosis of various B-cell disorders, including B-cell malignancies and autoimmune diseases. In more particular embodiments, the humanized anti-CD19 antibodies may comprise one or more framework region amino acid substitutions designed to improve protein stability, antibody binding and/or expression levels. In a particularly preferred embodiment, the substitutions comprise a Ser91Phe substitution in the hA19 VH sequence.
