Chronic T-cell leukaemias. III. T-colonies, PHA response and correlation with membrane phenotype.

The functional capacity of T lymphocytes from 28 cases of chronic T-cell leukaemia--T-CLL, T-PLL, T-LCL and Sézary syndrome--was evaluated in a T-colony forming system and in a PHA response assay. Reduced or absent T-colony growth was observed in 23 cases (82%) while in five the growth was normal. Although a good correlation was generally observed between colony formation and PHA transformation, in a few cases a low PHA response was accompanied by moderate colony growth and vice versa. Characterization of the leukaemic T lymphocytes using monoclonal antibodies (OKT series) indicates that cases with a helper/inducer phenotype (OKT4+) showed moderately reduced or near-normal T-colony numbers, whilst cases with a suppressor/cytotoxic phenotype (OKT8+)--confined to T-CLL in this study--had a very low or absent colony growth. The functional abnormalities reported here suggest that neoplastic T-cells with a helper/inducer phenotype show a low proliferative response in the assay systems used, although expressing mature T-cell characteristics. The low growth observed in T-CLL confirms that cells with a suppressor/cytotoxic phenotype form few T-cell colonies.