Increase in cytoplasmic free calcium concentration initiated by T3 antigen stimulation is imparied in adult T-cell leukemia cells

We studied the change in cytoplasmic free calcium ion concentration ([Ca²⁺]i) in the peripheral blood leukemic cells from adult T-cell leukemia (ATL) patients stimulated by anti-T3(CD3) or anti-T11(CD2) antibodies in order to see whether there is an abnormal response in the early activation processes following T3 or T11 antigen stimulation. Peripheral blood mononuclear cells (PBMC) from four T-cell chronic lymphocytic leukemia (T-CLL) patients showed a rapid and clear increase in [Ca²⁺]i (from 165 ± 26 nM to more than 299 nM) when stimulated by OKT3 antibody and anti-mouse IgG antibody. This response was comparable to that of PBMC from 10 normal individuals (from 151 ± 20 nM to 252 ± 34 nM). In contrast, PBMC from 10 ATL patients showed only a slight increase in [Ca²⁺]i (from 137 ± 21 nM to 176 ± 32 nM) following T3 stimulation. The experiments with higher concentrations of OKT3 antibody suggested that this attenuated increase in [Ca²⁺]i in ATL cells was not exclusively due to impaired expression of T3 antigen. The [Ca²⁺]i increase in ATL cells induced by the stimulation with two anti-T11 antibodies recognizing different epitopes of the T11 antigen, however, was comparable to that of normal PBMC. The abnormal response of [Ca²⁺]i to the T-cell receptor /T3 antigen stimulation in ATL may be related to dysfunction or leukemogenesis of HTLV-I-infected cells.