Effect of chemotherapy and stem cell transplantation on T lymphocyte clones in familial haemophagocytic lymphohistiocytosis

Familial haemophagocytic lymphohistiocytosis (FHL) is a rare disorder in infancy, curative only by an allogeneic stem cell transplantation (SCT). We recently confirmed the clonal evidence of T cells in FHL. To confirm the effect of chemotherapy and SCT in FHL, the change of T-cell clones was analysed in two patients using inverse reverse transcription-polymerase chain reaction (RT-PCR) of the T-cell receptor variable region (TCR V) gene, followed by PCR for the junctional region (Jβ-PCR), a single-strand conformation polymorphism (SSCP) and sequencing analysis at diagnosis, after chemotherapy and after SCT. A high frequency (> 15%) of αβ T-cell clones and a predominant bias (Jβ1:Jβ2, 85:15) for the Jβ1 subgroup were observed in the two patients at diagnosis. In one patient, however, an inverted predominant bias (Jβ1:Jβ2, 9:91) for the Jβ2 subgroup and oligoclonal expansion were observed at relapse after chemotherapy. In the other patient, correction of both restricted Jβ cluster usage and variation of TCR were observed after chemotherapy and SCT. Using sequence analysis, the clonal T cells detected at diagnosis were found to be substituted at low frequency (< 0.75%) by several new clones after chemotherapy and SCT. These results indicate that any genetic defect could influence the regulation of the T-cell network, and normalization of both the variation in each Vβ repertoire and the Jβ1/Jβ2 ratio is needed to achieve remission, and might support the rationale that the only acceptable curative therapy of FHL is allogeneic SCT.