"In vitro" colony growth of blood T-lymphocytes from B-cell chronic lymphocytic leukemia

T-lymphocyte colony formation in agar culture was investigated in 20 untreated B-cell Chronic Lymphocytic Leukemia (CLL) patients in stage O. As compared to the controls, colony growth was very poor when unseparated peripheral-blood lymphocytes from CLL-patients were seeded. The number of colonies was greatly higher when T-cell enriched fractions from CLL were plated; however, they failed to reach the normal range even in this experimental condition. The role of adherent cells in the colony growth was also investigated. Depletion of these cells resulted in impaired colony generation either in normals or in CLL-patients, which was subsequently restored by the addition of the same adherent cells. In the patients investigated in this study, an imbalance of T-subsets was found with increase of OKT8-positive cells (T-suppressors). When the number of colonies and the percentage of OKT8-positive cells were plotted, an inverse correlation was found. Conversely, a linear relationship was detected between the percentage of OKT4-positive cells (T-helpers) and the values of colonies. On the basis of the present experiments, it is suggested that the defective colony growth of T-cell fractions in B-cell CLL may be related to the low number of OKT4-positive cells plated, which are known to be mainly responsible for the colony generation in agar culture.