BOVINE LEUKEMIA VIRUS-GP51 ANTIGEN EXPRESSION IS ASSOCIATED WITH CD5 AND IGM MARKERS ON INFECTED LYMPHOCYTES

Cows that develop a persistent lymphocytosis (PL) as a result of bovin e leukemia virus (BLV) infection develop massive proliferation of B-ly mphocytes expressing both IgM and CD5 markers. The association of thes e two markers on peripheral blood mononuclear cells (PBMC) derived fro m BLV-infected cows and also expressing BLV-gp51 antigen marker on the se cells was determined by three-color cytometric analysis. After in v itro cultivation of PBMC in the presence of PHA for 24 h, the mean per centages of marker-reactive cells of five PL+ cows were as follows; 43 % +/- 4.5 of the PBMC expressed BLV-gp51 antigen; 90% +/- 1.6 of these cells expressed both IgM and CD5 at the same time, whereas but 7.5% /- 1.9 expressed only IgM and 2.9% +/- 0.4 expressed only CD5. The PBM C, IgM positive cells accounted for 77.8% +/- 6.8, while both CD5 and BLV-gp51 were detected simultaneously on 52.0% +/- 2.4 of the IgM(+) c ells, while the CD5 marker and BLV-gp51 antigen were detected independ ently on 35.0% +/- 1.9 and in 9.0% +/- 3.1, respectively of the IgM(+) cells. Of the CD5(+) cells (equivalent to 75.5% +/- 9.0 of the PBMC), 54.7% +/- 4.7 expressed simultaneously IgM and BLV-gp51, while BLV-gp 51 and IgM were expressed separately by 3.0% +/- 0.5 and 37.8% +/- 3.3 , respectively. An association between the B-cell phenotype and BLV tr opism might exist. It is also possible that cells bearing both IgM and CD5 markers are the main target cells for BLV infection. (C) 1997 Els evier Science B.V.