OKM1-positive T-cell leukemias. Relationships among morphologic features, phenotype, and functional activities

Area of Science:

• Immunology
• Hematology
• Oncology

Background:

• Leukemic T-cells exhibit diverse morphologic and functional characteristics.
• Understanding the phenotype of these cells is crucial for classification and treatment.

Purpose of the Study:

• To investigate the morphologic features, phenotype, and functions of OKM1+ leukemic T-cells.
• To identify distinct subgroups within OKM1+ leukemic T-cells.

Main Methods:

• Morphologic analysis of leukemic T-cells.
• Immunophenotyping using a panel of monoclonal antibodies (e.g., OKM1, ER, OKT3, OKT4, OKT8, Leu-7, Leu-11b, anti-Tac).
• Functional assays including antibody-dependent cell-mediated cytotoxicity (ADCC), natural killer (NK) activity, and B-cell differentiation assays.

Main Results:

• Two chronic lymphocytic leukemia (CLL) patients had large granular lymphocyte (LGL) morphology; two acute lymphocytic leukemia (ALL) patients had L2 morphology.
• One CLL patient's cells were OKM1+, ER+, OKT3+, OKT4+, OKT8-, OKIa1-, EA gamma+, Leu-7+, Leu-11b+, anti-Tac-, with ADCC and helper T-cell activity.
• The other CLL patient's cells lacked Leu-7, Leu-11b, ADCC, and NK activity. ALL cells were ER+, OKM1+, Leu-7-, Leu-11-, with variable EA gamma expression and no cytotoxicity.

Conclusions:

• OKM1+ leukemic T-cells comprise at least two subgroups: LGL-type and lymphoblastic-type.
• The observed phenotypes are novel and suggest the emergence of a distinct, small lymphocyte subset in T-cell leukemias.