VENULAR ENDOTHELIUM BINDING-MOLECULES CD44 AND LECAM-1 IN NORMAL AND MALIGNANT B-CELL POPULATIONS - A COMPARATIVE-STUDY

Lymphocytes leave the blood via post-capillary venules by binding initially to their specialized endothelium. CD44 is a 80-90 kDa hyaluronate-binding glycoprotein involved in binding to endothelium of high endothelial venules (HEV). LECAM-1 is a 75-85 kDa glycoprotein with lectin activity interacting with human peripheral lymph node vascular addressin (PNAd) on HEV. This immunohistochemical study shows that CD44 and LECAM-1 are essentially coordinately expressed on B-lymphocytes. The mode and level of CD44/LECAM-1 expression dissect the peripheral B-cell development into stages that are closely linked to morphologically defined B-cell compartments. Although statistically correlated in B-cell leukaemias (p < 0. 0009) and extranodal B-cell lymphomas (p < 0.003), expression of both molecules was less stringently coordinated in 127 B-cell neoplasms examined. B-cell chronic lymphocytic leukaemia, hairy cell leukaemia and mantle zone lymphoma were CD44/LECAM-1 positive, thus corresponding to their reactive counterparts. Correspondingly, follicular centre cell-derived lymphomas were devoid of both markers. Conversely, CD44 and LEC-AM-1 were infrequently detectable in extranodal malignant B-cell neoplasms, irrespective of their maturational state. Presence versus absence of CD44 and LECAM-1, alone or together, determined neither the leukaemic versus aleukaemic state nor the nodal versus extranodal tumour-forming phenotype of a B-cell tumour.