Lymphocytes from patients receiving lithium do not inhibit CFU-C growth

Lymphocyte subset levels and function were examined in 12 patients on lithium therapy and in 11 healthy hospital personnel. Co-culture of allogeneic human bone marrow cells with monocyte-depleted lymphocyte preparations revealed that CFU-C formation was significantly reduced (mean 43% inhibition) in the presence of normal lymphocytes but not with the patients' lymphocytes (less than 5% inhibition). This did not reflect numerical changes in lymphocyte subsets, since these were similar for control and lithium subjects. T colony formation was significantly depressed in the patient group (P less than 0.05), whereas B colony numbers were similar in both groups (P greater than 0.1). The possible role of HLA-incompatibility affecting CFU-C growth was investigated in co-culture experiments, using lymphocytes from HLA-identical twins, one of whom was receiving lithium. In four separate co-culture experiments, the inhibitory effect was shown with lymphocytes from the non-lithium twin but was not demonstrated by the lithium subject. Addition of lithium in vitro to co-cultures of normal marrow and lymphocytes was found to negate the inhibitory phenomenon in a dose-related manner. It is postulated that granulocytosis induced by the administration of lithium may be a manifestation of changes in a lymphocytic control system.