Cytosolic free [Ca2+] in single T-lymphocytes from depressed patients and healthy controls.

Human lymphocytes are widely used as peripheral models for central neurones. Alterations in immune function have been reported in depressed patients, e.g. mitogen-induced proliferation is impaired during depression. One possible causative mechanism could be altered [Ca2+]i regulation. Phytohaemagglutinin (PHA)-induced rise of [Ca2+]i has been found to be diminished in lymphocyte suspensions from depressed patients (Ecker et al., this issue). We measured PHA-induced rise of [Ca2+]i in single Fura-2 AM-loaded T11+ lymphocytes of patients with major depression and controls to further analyse [Ca2+]i regulation in depression. The [Ca2+]i of resting lymphocytes was 57 +/- 2 nmol/l (mean +/- SEM). There was no difference in resting [Ca2+]i of resting lymphocytes of patients and controls. PHA evoked an increase of [Ca2+]i an 7 out of 14 cells from control subjects up to 400-500 nmol/l. In contrast, only 4 out of 13 cells from depressed patients showed an increase of [Ca2+]i up to 200 nmol/l. In a small fraction of cells from both groups the [Ca2+]i signal is oscillating. Our preliminary data confirm alteration of [Ca2+]i regulation in lymphocytes of depressed patients.