Background.Mesenchymal stem cells (MSC) are currently extensively studied because of their abilities to support haemopoiesis, to modulate immune reactions (including GVHD) and to differentiate into specialized tissues (cartilage, bone, smooth muscle). In our laboratory we studied growth properties of mesenchymal stem cells in patients with lymphoid malignancies. Materials and methods. 10 ml of bone marrow aspirate was taken from patients undergoing routine diagnostic or control trephine biopsy. After separation of mononuclear cells (MNC), adhesive MNCs and fibroblasts were counted and their number expressed per 105 total MNCs. Mesenchymal cells were grown in complete medium (α-MEM + 20% fetal bovine serum + glutamine + antibiotics). We evaluated the number of colonies from the 1st passage (per 105 total MNCs = CFU-F1), number of MSCs from the 1st passage and number of MSC colonies grown from the 2nd passage (CFU-F2) after seeding in concentrations of 1.5, 3, 5 a 10 cells/cm2. Results. Samples were taken from 44 patients; from 15 of them bilateral samples were obtained. The number of CFU-F1 correlated significantly only with the number of adhesive fibroblasts. The number of CFU-F2 colonies showed an approximately linear correlation with the concentrations of cells seeded. Patients with chronic lymphocytic leukaemia and multiple myeloma had higher CFU-F2 counts than patientswith lymphoma.When bilateral samples were taken, very good correlations between the counts of adherent MNCs, fibroblasts, CFU-F1 and CFU-F2 were observed in both samples from the same patient. Conclusion. Our method of evaluation of MSC numbers in bone marrow seems reproducible and reliable. Different growth characteristics of MSCs in patients with different lymphoidmalignancies can be caused by different profiles of cytokine secretion, which can in turn influence the pathogenesis of these diseases.

        Key words: mesenchymal stem cells, lymphoma, chronic lymphocytic leukaemia, myeloma