Two groups of U937 promonocytic cells were obtained by limiting dilution cloning which differed strikingly in their ability to support human immunodeficiency virus 1 ( HIV-1 ) replication .
two groups of u937 promonocytic cells were obtained by limiting dilution cloning which differed strikingly in their ability to support human immunodeficiency virus 1 ( hiv-1 ) replication .
O O O B-cell_line I-cell_line I-cell_line O O O O O O O O O O O O O O B-virus I-virus I-virus I-virus O B-virus O O O