ANALYSIS OF T-CELL CLONALITY IN BONE-MARROW OF PATIENTS WITH ACQUIREDAPLASTIC-ANEMIA

Acquired aplastic anaemia (AA) represents a state of bone marrow (BM) failure which is characterized by BM hypocellularity and pancytopenia. It has been hypothesized that in some AA patients, bone marrow failur e is secondary to the targeted destruction of haemopoietic stem cells by autoreactive T cells. The response of T cells to antigenic stimulat ion has been shown, in a number of animal models and in autoimmune dis eases, to result in the (oligo)clonal expansion of positively reacting T cells. For this reason, we studied the utilization of 24 T-cell rec eptor-beta variable gene segments (TCRBV) and the clonality in BM aspi rates and peripheral blood (PB) of seven AA patients. BM from transpla nt donors served as controls. Determination of TCRBV gene segment usag e revealed no significant differences between patients and controls. C lonality within each family was analysed by single-strand conformation polymorphism (SSCP) analysis. Clonal and clonally predominant bands w ere seen in BM of three AA patients in live to eight TCRBV families. C lonal rearrangements were encountered less often in BM of control subj ects. In conclusion, our results suggest an antigen-driven T-cell resp onse in the BM of predominantly AA patients resulting in oligoclonal T -cell outgrowth.