Analysis of T-cell clonality in bone marrow of patients with acquired aplastic anaemia

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 failure is secondary to the targeted destruction of haemopoietic stem cells by autoreactive T cells. The response of T cells to antigenic stimulation has been shown, in a number of animal models and in autoimmune diseases, to result in the (oligo)clonal expansion of positively reacting T cells. For this reason, we studied the utilization of 24 T-cell receptor-variable gene segments (TCRBV) and the clonality in BM aspirates and peripheral blood (PB) of seven AA patients. BM from transplant donors served as controls. Determination of TCRBV gene segment usage revealed no significant differences between patients and controls. Clonality within each family was analysed by single-strand conformation polymorphism (SSCP) analysis. Clonal and clonally predominant bands were seen in BM of three AA patients in five to eight TCRBV families. Clonal rearrangements were encountered less often in BM of control subjects. In conclusion, our results suggest an antigen-driven T-cell response in the BM of predominantly AA patients resulting in oligoclonal T-cell outgrowth.