Molecular single cell studies of normal and transformed lymphocytes.

The polymerase chain reaction allows the characterization of RNA and DNA sequences from single cells. Methods were established to analyse single cells isolated from suspension or by multicolour flow cytometry. We established a method to isolate single immunostained cells from frozen tissue sections and to analyse those cells for immunoglobulin gene rearrangements. This method was first used to study B cell differentiation within human germinal centres. In another series of experiments, Hodgkin and Reed-Sternberg (HRS) cells from a total of 14 cases of HD were analysed for B lineage derivation and clonality. In 13 of the 14 cases, clonal V gene rearrangements were identified. This shows that HRS cells generally represent the outgrowth of a clonal population of B cells. The detection of somatic mutations in all VH gene rearrangements amplified from HRS cells and the nature of those mutations identifies a GC B cell as the HRS precursor.