Antigen interaction with B cells in two proliferative disorders : CLL and MGUS

• The aim of the work presented in this thesis was to elucidate B cell interaction with antigen in the two B cell proliferative disorders chronic lymphocytic leukemia (CLL) and monoclonal gammopathy of undetermined significance (MGUS). In the first part we investigated the antigen specificity of CLL cells and characterized Epstein-Barr virus (EBV)-transformed CLL cell lines with regard to phenotype and genotype. The second part consists of studies on the antigen presenting capacity of myelin protein zero (P0) specific MGUS B cells and their relation to T cells and development of polyneuropathy.The aim of the work presented in this thesis was to elucidate B cell interaction with antigen in the two B cell proliferative disorders chronic lymphocytic leukemia (CLL) and monoclonal gammopathy of undetermined significance (MGUS). In the first part we investigated the antigen specificity of CLL cells and characterized Epstein-Barr virus (EBV)-transformed CLL cell lines with regard to phenotype and genotype. The second part consists of studies on the antigen presenting capacity of myelin protein zero (P0) specific MGUS B cells and their relation to T cells and development of polyneuropathy.CLL cells are considered antigen experienced and different patient-derived CLL cells expressing B cell receptors (BCR) with highly homologous antigen binding sites are believed to have been selected by a common antigen at some point during the leukemogenesis. In paper I we investigated the antigen specificity of CLL-cell derived antibodies (Abs) with various IGHV gene usage and stereotyped BCR subset belonging. Identified CLL antigens included vimentin, filamin B, cofilin-1, proline rich acidic protein-1, cardiolipin, oxidized low density lipoprotein and Streptococcus pneumoniae capsular polysaccharides. Many of the CLL Abs studied displayed an oligo- or polyreactive antigen binding pattern and the identified antigens were either associated with apoptotic cells or microbial infection. This is similar to what has been described for innate natural antibodies, possibly indicating that CLL cells are derived from a natural-antibody- producing B cell population. Further characterization of CLL homology subset-2 antigen specificity showed binding to glands in human gastric mucosa corpus tissue sections for a CLL homology subset-2 Ab with HCDR3 motif-1, suggesting that this CLL subset recognize an autoantigen much like the CLL Abs tested in Paper I.Characterization of EBV-transformed CLL and normal lymphoblastoid cell lines (LCLs) in paper II showed that eight of the CLL cell lines were verified to be of authentic neoplastic origin. Indication for a biclonal CLL was found in two of the cell lines and two of the presumably normal LCLs turned out to represent the malignant CLL clone. For three cell lines no conclusive evidence for CLL origin could be found emphasizing the importance of verifying the identity of cell lines used in research.

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