Abstract:

Objective To analyze the variation of CD5 caused by different fluorescein-labeled antibodies on B cells in patients with chronic lymphocytic leukemia(CLL) and the influence on clinical diagnosis. Methods Flow cytometry and SYSMEX XE2100 automated hematology analyzer were used for the detection of immunophenotype and blood cell counts of 3 CLL patients with different expression intensities of CD5, respectively. 1 patient with B-cell acute lymphocytic leukemia(B-ALL) was selected as negative control. Result In 4 patients with abnormal B lymphocytes, using fluorescein isothiocyanate(FITC) fluorescein-labeled antibody, no independent groups expressing CD5 were identified, and the proportions of CD5 positive cells were 47.1%, 17.7%, 6.7% and 7.9%. For ≥20% as standard, there was only 1 positive case. Re-tested with PE-Cy7 fluorescein-labeled antibody, however, there were independent groups of CD5 positive cells in case 1 and 2, and there was still a continuous expression pattern of CD5 in case 3. The proportions of CD5 positive cells increased to 91.1%, 70.3% and 38.2% in these 3 specimens from CLL patients. In case 4, the specimen from B-ALL patient, the proportions of CD5 positive cells were negative in the 2 conditions. Case 1, 2 and 3 were typical CLL phenotyping. Conclusions CD5 is often abnormally expressed on B cells in CLL patients, but its expression intensity is significantly lower than that on T cells. Using weak fluorescein-labeled antibodies might miss CD5 expression on B cells, and thus it will affect the clinical diagnosis because of leak detection. It should select appropriate fluorescein-labeled antibodies for weakly expressed antigens and conduct validation and comparison to determine its accuracy, which is an important safeguard for the provision of correct disease phenotype.

Key words: CD5, Immunophenotype, Chronic lymphocytic leukemia, Flow cytometry, Leak detection