An immunoglobulin that specifically binds CD20 and exhibits increased complement-dependent cytotoxicity as compared to rituximab, wherein said immunoglobulin is an IgG1 immunoglobulin, and wherein said immunoglobulin is selected from the group consisting of: a) an immunoglobulin comprising a variable light (V L) domain having the amino acid sequence set forth in SEQ ID NO: 10, and a variable heavy (V H) domain having the amino acid sequence set forth in SEQ ID NO: 12; b) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 10, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 13; c) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 10, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 14; d) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 10, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 15; e) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 10, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 16; f) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 10, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 17; g) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 10, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 18; and h) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 11, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 16. a) an immunoglobulin comprising a variable light (V L) domain having the amino acid sequence set forth in SEQ ID NO: 10, and a variable heavy (V H) domain having the amino acid sequence set forth in SEQ ID NO: 12; b) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 10, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 13; c) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 10, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 14; d) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 10, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 15; e) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 10, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 16; f) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 10, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 17; g) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 10, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 18; and h) an immunoglobulin comprising a V L domain having the amino acid sequence set forth in SEQ ID NO: 11, and a V H domain having the amino acid sequence set forth in SEQ ID NO: 16.