CD5 and cCLLa Expression in Chronic Lymphocytic Leukemia (CLL): Demonstration of Their Relative Prevalence and that of Other Common B-CLL Markers

Abstract

Chronic lymphocytic leukemia (CLL) is a malignant lymphoproliferation most frequently involving B-cells. Characteristically, B-CLL cells express a number of surface antigens collectively known as CLL markers. Some of the most prevalent CLL markers have been used for the immunophenotypic diagnosis and for targeted immunotherapy of B-CLL. In order to ascertain the relative prevalence of CLL markers, we assessed the immunophenotypic profile of 112 consecutive B-CLL patients. Patients were diagnosed according to International CLL Workshop criteria extended to include preclinical B-CLL. Immunophenotypic profiles were based on fluorescence microscopy and flow cytometry. In decreasing order of frequency, the B-CLL clone was cCLLa ⁺, CD19⁺, MosIg⁺ or CD5⁺ in 100%, 97%, 92% and 78% of patients, respectively. Likewise, in 14 CD5^- patients the B-CLL clone was cCLLa, CD19⁺ and MosIg⁺ in 100%, 100% and 93% of patients, respectively. Co-expression of cCLLa, CD 19 and Moslgs by CD5^- B-CLL cells was inferred from the high correlation (r > 0.99) among cell subsets expressing all three markers, and was confirmed by two color flow cytometry (n = 25). Except for a smaller circulating clone, CD5., B-CLL was clinically, hematologically and immunophenotypically indistinguishable from CD5⁺ B-CLL. These data indicate that a substantial fraction of B-CLL patients are CD5^-. More prevalent CLL markers such as the cCLLa might be more suitable for targeted immunotherapy.

Key Words:

• CD5
• cCLLa chronic lymphocytic leukemia
• B-CLL markers