This invention relates to monoclonal antibodies which affect growth and/or differentiation of B cells in the germinal center. The monoclonal antibodies of the present invention are useful for treating disorders characterized by an abnormal growth and/or differentiation of B cells, including lymphoma, multiple myeloma and autoimmune diseases.
As B cells mature, B cells leave the bone marrow and migrate to the lymphoid follicles of lymph nodes and spleen, and other peripheral lymphoid tissues. In the absence of antigen, mature B cells pass from blood into primary lymphoid follicles and then back into peripheral blood. If B cells encounter antigens and appropriate helper T-cells on entering the lymphoid tissue and become activated, B cells proliferate first in the T-cell areas, forming primary foci from which proliferating B cells migrate to the primary follicle forming a secondary follicle with a germinal center (or xe2x80x9cGCxe2x80x9d).
The GC of the secondary lymphoid follicles is a unique automical site where antigen-activated B cells undergo clonal expansion and selection to differentiate into memory B cells or into antibody-secreting plasma cells. Follicular dendritic cell xe2x80x9cFDCxe2x80x9d is a stromal cell located in the GC which is essential for B cell growth and lymphomagenesis. The GC reaction is initiated by rapid proliferation of Ag-stimulated B cells in association with follicular dendritic cells or xe2x80x9cFDCsxe2x80x9d (MacLennan, I. C., Annu. Rev. Immunol. 12:117-139, 1994). The GC-B cells exhibit features distinct from naive or memory B cells in that GC-B cells display a unique pattern of Ag expression on the cell surface (Liu, Y. J., et al., Immunity 2:239-248, 1995), undergo Ag receptor-mediated apoptosis (Billian, G., P., et al., Eur. J. Immunol. 27:405-414, 1997), and require essential survival signals from FDCs, as disruption of FDC-B cell clusters results in apoptosis of B cells (Kosco, M. H., et al., J. Immunol. 148:2331-2339, 1992; Koopman, G., et al., J. Immunol. 152:3760-3767, 1994). Observations made using lymphotoxin-xcex1 knockout mice further confirmed that the initial interaction between FDCs and B cells is essential for GC formation (Gonzalez, M., F., et al., J. Exp. Med. 187:997-1007, 1998; Fu, Y.-X., et al., J. Exp. Med. 187:1009-1018, 1998). T cells expressing CD40 ligand (CD40L) also play a pivotal role in the GC reaction, as evidenced in hyper-IgM patients and in mouse models that have null mutations in the CD40 (Kawabe, T. et al., Immunity 1:167-178, 1994) or CD40L genes (Renshaw, B. R., et al., J. Exp. Med. 180:1889-1900, 1994).
The genetic events that occur during the clonal expansion and selection of B cells at the GC include somatic mutation and isotype switching, which leads to the production of more efficient antibodies with high affinity to the invading microorganisms. At the same time, B cell lymphoma may arise in the GC of the secondary lymphoid follicles as a consequence of genetic instability and mobility during this cellular and molecular process.
Follicular lymphoma is the most common type of non-Hodgkin""s lymphoma in the west. In the early stage, follicular lymphoma is usually indolent, regressing spontaneously and showing susceptibility to chemotherapy (Horning, S. J., et al., N. Engl. J. Med. 311:1471-1475, 1984). However, this tumor usually recurs and can undergo blast transformation to an aggressive form, ultimately becoming a fatal disease. The generation and blast transformation of this tumor is closely associated with FDCs in the GC (Petrasch, S., et al., Br. J. Haematol. 80:21-26, 1992).
Multiple myeloma is a tumor usually found in bone marrow. Myeloma cells grow aggressively and, like plasma cells (PCs) from which myeloma cells are believed to originate, secrete immunoglobulins. PCs are generated in the GC as a result of clonal expansion and selection, during which process somatic mutation and isotype switching occur. PCs then migrate to bone marrow to expand in the presence of stroma cells. As a consequence of the genetic mobility and mutability involved in the generation and translocation of PCs, malignant transformation may occur which leads to the development of multiple myeloma.
The present invention provides monoclonal antibodies which interfere with the interactions between FDCs and B cells, thereby suppressing the growth and/or differentiation of B cells, as well as tumorigenesis of B cells in vivo. The monoclonal antibodies of the present invention are useful for treating disorders characterized by an abnormal growth and/or differentiation of B cells, including lymphoma, multiple myeloma and autoimmune diseases.
A preferred monoclonal antibody of the present invention is mAb 8D6. The hybridoma cell line which produces mAb 8D6 was deposited on Mar. 13, 2001 with the American Type Culture Collection, 10801 University Boulevard, Manassas, Va. 20110-2209 (ATCC deposit number designated as PTA-3231)
Another preferred monoclonal antibody of the present invention is mAb 4G10. The hybridoma cell line which produces mAb 4G10 was deposited on Mar. 13, 2001 with the American Type Culture Collection, 10801 University Boulevard, Manassas, Va. 20110-2209 (ATCC#).
Hybridoma cell lines which produce mAb 8D6 and mAb 4G10, respectively, are provided in another embodiment of the present invention.
Functional derivatives of the monoclonal antibodies of the present invention are also provided, including, but not limited to, Fab, Fabxe2x80x2, F(abxe2x80x2)2, single chain antibodies, chimeric antibodies and the like.
Another embodiment of the present invention is directed to pharmaceutical compositions. The pharmaceutical compositions include a monoclonal antibody of the present invention or a functional derivative thereof, and a pharmaceutically acceptable carrier.
A further aspect of the invention provides methods of treating a subject suffering a pathological condition characterized by abnormal B cell growth or differentiation by administering to the subject a therapeutically effective amount of a monoclonal antibody of the present invention or a functional derivative thereof. Pathological conditions which can be treated by practicing the present methods include lymphoma, multiple myeloma and autoimmune diseases.