Expression of alternatively spliced exons of CD45 in peripheral T-cell lymphomas and its correlation to the expression of adhesion molecules

The expression of CD45R0, CD45RA, and CD45RB (n = 35) was examined in paraffin sections from 35 T-cell lymphomas. A protocol including microwave irradiation for the demasking of antigens was used for the detection of RA and RB. CD45 RC was studied in the 15 lymphomas for which frozen material was available. In addition to the CD45 isoforms, the expression of adhesion molecules CD44, CD38, LFA-1, CD54 (ICAM-1), CD62L (L-selectin), and O-acetyl GD3 was studied, most of them requiring staining from frozen sections. The expression of alternatively spliced exons of CD45 was, with one exception, compatible with a memory type of T lymphocyte, i.e., expressing R0 and RB but not RA and RC. RB showed some heterogenicity of staining, especially when pleomorphic T-cell lymphomas with medium-sized cells and small/medium sized cells were studied. It had been suggested earlier that the expression of alternatively spliced exons of CD45 is solely dependent on the number of CD45 expressed, and that the expression of these will follow the hierarchy RB > RA = RC. The results of this study are compatible with this model. The lack of RA in lymphomas is in some contrast to earlier findings concerning T-cell leukemias. Possible reasons for this divergence are discussed. The expression of adhesion molecules was also compatible with a memory phenotype. CD44, CD38, LFA 1, and ICAM-1 were widely expressed, whereas CD62L (L-selectin) was not. Interestingly, CD62 was not expressed in several nodal sites, although the lymphomas in question otherwise conformed to a memory phenotype. The expression of adhesion molecules therefore correlated well with the expression of alternatively spliced exons of CD45. In individual cases, however, some discrepancies in this respect arose, i.e., cells expressing molecules associated both with a memory phenotype and a naive phenotype. The lymphomas expressed O-acetyl GD3 ganglio-side only in a few cases, contrary to the pattern seen in normal R0-positive cells in which >80% of the cells stain positive for 27A.