Immunologic characteristics of CD99 negative B cells and rescue from the H-RS phenotype by exogenous expression of CD99. (A) Deregulation of soluble CD40L-induced cytokine secretion in CD99-deficient B cells. Cells were cultured in RPMI media alone or in media supplemented with soluble CD40L (supernatant, 1:10 ratio). (B) Cell-cycle analysis. Flow cytometric analysis was performed on asynchronously proliferating Vec-TF (top) or AS-TF IM9 cells (bottom). The x-axis shows DNA content and the y-axis shows the number of cells. (C) Growth curve of CD99-deficient IM9 cells. The same number (5 × 104/mL) of cells was plated in 10% FCS-DMEM media at day 0. The total cell numbers were counted at the indicated days. The result of thymidine uptake is shown in the box. (D) Flow cytometric analysis of Mut-IM9 and CD99-TF Mut-IM9 cells. (E) Flow cytometric analysis of Vec-TF and CD99-TF L428 cells. Note the tight relation between the forward/side scatter profile and the expression of CD99 and MHC class I.
