MHCI negative cells express low levels of Ki67. (A) A representative flow cytometric analysis of the expression of proliferation antigen Ki67 in MHCI positive, and MHCI negative cells. Gates were set using isotype control antibodies and single color control antibodies. In this experiment 3.9% of MHCI positive cells express Ki67, while only 0.9% of MHCI negative cells express Ki67. Although the exact values of proliferating population may vary from experiment to experiment the ratio of MHCI positive and MHCI negative proliferating populations stay constant. This result demonstrate quiescent nature of MHCI negative cells. (B) Single positive isotype control for PE. (C) Single positive control for FITC. (D) Secondary control.