6th ESACP Congress, Heidelberg, April 7-11, 1999

A021
IMMUNOGLOBULIN V GENE REARRANGEMENTS AS CLONAL MARKERS FOR MICROMANIPULATED SINGLE CELLS FROM MALIGNANT LYMPHOMAS
Bräuninger A, Hansmann ML

Dept.Pathology,University of Frankfurt, Germany

Somatic recombination of immunoglobulin V genes creates unique sequences in the joining regions, which are clonal markers for B cells. Thus, PCR amplification and subsequent direct sequencing of rearranged V gene segments allows the analysis of clonal relationships between single cells. As rearranged immunoglobulins of B cells participating in a germinal center reaction are somatically mutated, such analysis allows also the assignment of the lymphoma precursor cells to a pre- or post-germinal center stage or, if ongoing mutation is detected, to mutating germinal center B cells. Using this approch we have recently analysed six cases of T cell-rich B cell lymphoma. In all cases a mutating germinal center B cell, which seems to be selected for expression of a functional antigen receptor, was identified as the lymphoma precursor. In addition, we analysed the clonal relationship of the Hodgkin/Reed-Sternberg cells of Hodgkins disease (HD) and the neoplastic cells of non Hodgkin lymphomas (NHL) occuring in the same patient. In one case HD and Follicular lymphoma were found simultaneous in one lymphe node, whereas in another case T cell-rich B cell lymphoma of the skin (surgical removed without further therapy) was followed by HD three years later. Analysis of the rearranged V genes from the CD20 positive cells of the NHLs and CD30 positive cells of the HDs revealed clonal relationships between the NHLs and HDs in both cases. The rearranged V genes in the two different lymphomas of each case carried shared as well as unique mutations. Intraclonal diversity due to ongoing mutation was observed in both NHLs but was absent or only marginal in both HDs. These findings provide further evidence for the B cell origin of Hodgkin/Reed-Sternberg cells and indicate that, at least in the two cases analysed, NHLs and HDs may share some common transforming events.