Visual inspection versus quantitative flow cytometry to detect aberrant CD2 expression in malignant T cells

Abstract

Background: Abnormal levels of T-cell antigen expression occur in T-cell neoplasia. We examined CD2 expression in malignant and normal T cells to determine if the level of CD2 expression differed significantly and if quantitation assisted in detecting this difference.

Method: Flow cytometric immunophenotypic (FCI) evaluation was performed on specimens from 36 patients with mature T-cell neoplasia. Abnormal T cells were identified based upon the abnormal FCI and morphology. Levels of CD2 expression were quantitated using 1:1 PE conjugates of anti-CD2 and QuantiBRITE bead standards to calculate the antibodies bound per cell (ABC). The efficacy of ABC measurement versus simple examination of dots plots was compared.

Results: Abnormal levels of CD2 expression were frequently observed in mature T-cell malignancies. The CD2 ABC values were highly sensitive in detecting differences between malignant and normal T cells (P = 0.0028). In most cases (24/32 specimens, 75%), CD2 ABCs differed by >20%. CD2 ABCs had high variability in normal T cells.

Conclusions: CD2 expression by malignant T cells differed significantly from that of normal T-cells by CD2 ABC quantitation. The high variability in normal T-cell CD2 ABCs limited the determination of normal reference ranges and, thus, its utility in the diagnosis of T-cell neoplasia. However, examination of CD2 can help in detection of tumor cells when residual normal T cells are present for comparison. Moreover, the increased sensitivity of CD2 quantitation is valuable in confirming FCI cases where abnormalities in CD2 expression are difficult to appreciate by visual inspection alone.

Figure 1

Abnormal expression of CD2 in malignant T cells in 1) patient 4, 2) Patient 23 and 3) Patient 7. A.1) Abnormal T cells (red) have dim CD3, negative CD7, bright CD5 and slightly decreased CD2. 2) Abnormal T cells are CD3 positive, CD57 positive and have dim CD2. 3) Abnormal T cells have bright CD5, negative CD7, negative CD3 and bright CD2. B. Levels of CD2 Expression in Malignant and Normal T Cells as Measured by Anti-CD2 Clones S5.2 and MEDI-507: 1) Malignant T cells (arrow) have a lower level of CD2 expression as measured by S5.2 and MEDI-507. 2) Malignant T cells (arrow) have a lower level of CD2 expression as measured by S5.2 and MEDI-507. 3) Malignant T cells (arrow) have a higher level of CD2 expression as measured by S5.2 and MEDI-507.

Figure 1

Abnormal expression of CD2 in malignant T cells in 1) patient 4, 2) Patient 23 and 3) Patient 7. A.1) Abnormal T cells (red) have dim CD3, negative CD7, bright CD5 and slightly decreased CD2. 2) Abnormal T cells are CD3 positive, CD57 positive and have dim CD2. 3) Abnormal T cells have bright CD5, negative CD7, negative CD3 and bright CD2. B. Levels of CD2 Expression in Malignant and Normal T Cells as Measured by Anti-CD2 Clones S5.2 and MEDI-507: 1) Malignant T cells (arrow) have a lower level of CD2 expression as measured by S5.2 and MEDI-507. 2) Malignant T cells (arrow) have a lower level of CD2 expression as measured by S5.2 and MEDI-507. 3) Malignant T cells (arrow) have a higher level of CD2 expression as measured by S5.2 and MEDI-507.