Expression pattern of CD45 RA/RO isoformic antigens in T‐lineage neoplasms

Abstract

The expression of CD45 RA/RO antigen was investigated in neoplasms including cases expressing CD7 antigen as the sole pan-T antigen (n = 8), T-lineage acute lymphoblastic leukemia (ALL)/lymphoblastic lymphoma (LBL) at various stages of differentiation (n = 32), peripheral stage T-lineage leukemia (n = 10) and adult T-cell leukemia (ATL) (n = 14). The p56lck gene expression was also investigated in selected cases. The expression pattern of CD45 RA/RO antigen was defined as of RA, mixed, or RO type. All but one CD7+ CD5- CD2- case were of the RA type. The CD7+ CD5+ CD2- prothymic stage included seven RA and one mixed type cases. One CD7+ CD5- CD2+ case was of the RA type, but the other was of the RO type. The CD7+ CD5+ CD2+ prothymic stage included three RA and four mixed type cases. All seven CD3- CD4+ CD8+ (double-positive) thymic cases were of the RO type. The CD3+ CD4+ CD8+ (triple-positive) stage included two RO and three mixed-type cases. One CD3+ CD4+ CD8- late thymic case was of the mixed type. The peripheral stage cases included five RA, three RO, and two mixed type cases. All ATL cases were of the RO type. The expression of p56lck gene in the prothymic stage was less marked than that in the thymic stage. On the basis of these results, the following sequence of pattern of the CD45 RA/RO antigen expression along with T-lineage differentiation was reconstructed: prothymic stage [RA and mixed type]-->double-positive thymic stage [RO type]-->triple-positive thymic stage [RO and mixed type]-->peripheral stage [RA, mixed, and RO type]. While one RO-type CD7+ CD5- CD2- and one RO-type CD7+ CD5- CD2+ cases were not in accord with this sequence, the pattern of CD45 RA/RO antigen expression in most of T-lineage neoplasms could be determined by the respective stage of differentiation. The poor expression of the p56lck gene by the prothymic blasts compared with the thymic blasts may be related to the expression pattern of the CD45 RA/RO molecules, which exhibits phosphatase activity. The consistent RO-type expression in the ATL cases may reflect the activated status of the neoplastic T cells due to the presence of the HTLV-I gene. Alternatively, the target cells for HTLV-I-induced neoplastic transformation may possible be of the RO type.

IL-7–dependent human leukemia T-cell line as a valuable tool for drug discovery in T-ALL

“…Further evidence indicating that they are arrested in development as pre-T-ALL lymphoblasts is their lack of expression of CD34 and CD45RA and positivity for CD45RO. 23,24 Finally, analysis of TAIL7 cells at different culture time points showed that no significant phenotypic changes occurred, thus suggesting that continuous exposure to IL-7 did not induce cell differentiation.…”

EuroFlow antibody panels for standardized n-dimensional flow cytometric immunophenotyping of normal, reactive and malignant leukocytes

“…Additional markers (CD44, CD45RA, HLADR, CD13, CD33 and CD123) were added in order to contribute to maturational staging. 69, 182, 183, 184, 185 Some assess immaturity (e.g. CD123 186 ) or allow detection of the recently identified (very immature) ETP-ALL cases.…”

Protein tyrosine phosphatases

“…A very exciting new area of investigation is the involvement or loss of PTPases in human malignant diseases. The surface expression of CD45 has long been used as a marker for differentiation of leukemic cells (683,684). There is no evidence, however, that CD45 would be directly associated with the transforming event or progression of leukemias or lymphomas.…”