The CD44 receptor of the mouse LB T-cell lymphoma: Analysis of the isoformrepertoire and ligand binding properties by reverse-transcriptase polymerase chain reaction and antisense oligonucleotides

CD44 is a cell surface glycoprotein involved in cell migration and cell doc king in target organs via interactions with various ligands, including hyal uronic acid (HA), which is the principal ligand of this receptor. Alternati ve splicing generates many isoforms of CD44, including standard CD44 (CD44s ) and CD44 variants (CD44v). LB T-cell lymphoma, which predominantly expres ses CD44s, acquires additional CD44v and HA binding capacity after activati on with phorbol ester. The HA9 cell line, isolated from parental LB cells, expresses CD44v and constitutively binds HA, Downregulation of CD44v isofor ms of HA9 cells, by CD44v specific antisense inhibited their ability to bin d HA, indicating that CD44v, rather than CD44s, is associated with the acti vation status of this molecule. Using the reverse transcriptase polymerase chain reaction, we found that LB cells after infiltrating spleen and lymph nodes of BALB/c mice, contain an enriched repertoire of CD44v, implying tha t the metastatic cells acquired the activated form of this receptor.