CD98 antibodies differ in their ability to bind to the surface of U937 cells and their ability to induce homotypic aggregation.

(A) A panel of 7 CD98 antibodies was tested for the ability to bind U937 cells by means of flow cytometry. All antibodies were tested over a wide range of concentrations (1 to 30 μg/mL), and the histograms shown in the Figure are those obtained at saturating doses of antibody (between 1 and 30 μg/mL). (B) U937 cells were incubated with antibodies (at dilutions that induced maximal aggregation in each case, between 0.3 and 1.5 μg/mL in each case) for 6 hours, as described in “Materials and methods.” Images of cells in culture at this time point were obtained by means of an inverted phase contrast microscope (original magnification, ×40), attached to a video camera, and captured with National Institutes of Health (NIH) (Bethesda, MD) image software. (i) Medium alone. (ii) CD98-AHN-18 (CD98). (iii) BU53 (CD98). (iv) BU89 (CD98). (v) 4F2 (CD98). (vi) MEM 101A (CD29). (vii) 161-46 (CD43). (viii) E1/2 (CD44).