Generation of CD99-deficient IM9 cells and immunophenotyping. (A) Immunoblot and (B) Northern blot analyses of CD99-deficient IM9 cells. IM9 cells were transfected with either vector or antisense CD99 expression construct. The Vec-TF (V), AS-TF (A), and Mut-IM9 cells (M) were examined for CD99 expression. Actin was tested as an internal control. (C) Immunophenotypic analysis of AS-TF cells. The cells were first stained with control MoAb or with relevant primary MoAbs, and then with FITC-conjugated goat anti-mouse IgG antibody.