Yu Y, Rabinowitz R, Polliack A, Ben-Bassat H, Schlesinger M
The Hubert H. Humphrey Center for Experimental Medicine and Cancer Research, The Hebrew University-Hadassah Medical School, Jerusalem, 91120 Israel.
Eur J Haematol. 2002 Jan;68(1):22-30. doi: 10.1034/j.1600-0609.2002.00614.x.
Alternate splicing of exons of the CD45 molecule generates multiple isoforms differing in their molecular weights (MWs). In B-lymphocytes the CD45RA isoform was previously shown to be expressed on glycoproteins with MWs of 220 and 205 kDa, while the CD45RO isoform was expressed on glycoproteins with MW of 180 kDa. The present study demonstrated that B cell lymphomas and activated B-cells contain CD45 molecules with a MW of 185 kDa that express the CD45RA and CD45RC specificities but neither the CD45RB nor the CD45RO specificities. 185 kDa CD45RA+ molecules were detected in B cell lymphoma B lines, in Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines, and in tonsillar B cells, but not in normal, unstimulated peripheral blood B cells. These molecules were not detected in neoplastic and normal T cells. CD45RA+ 185 kDa molecules were present in B cells from three non-Hodgkin's patients in leukemic phase were not detected in B lymphocytes of seven of nine CLL patients tested. Trypsin treatment eliminated only 220 kDa CD45RA+ molecules but not 185 kDa CD45RA+ molecules, indicating that the 185 kDa CD45RA+ molecules are not expressed on the cell surface. Pulse-chase experiments, and studies on the effects of tunicamycin, neuraminidase and O-glycosidase, indicated that the 185 kDa molecules are partially glycosylated CD45RABC molecules that constitute precursors of the 220 kDa molecules. The high concentration of 185 kDa CD45RA+ molecules in B lymphoma cells and in activated B cells seems to reflect a high turnover of CD45RA+ molecules characteristic for these cells.
