Figure 7.

Natural killer (NK) cells are cytotoxic toward helper T (Th) cells through necrosis but not apoptosis. Memory CD4⁺ T cells from healthy subject PBMC were activated with anti-CD3, anti-CD28, and Th17 polarizing factors, either in the absence or presence of NK cells for 4 days. Samples were stained with CD3, CD56, 7AAD, and annexin V. Representative plots of T cells (CD4⁺CD56⁻) cultured without (A) or with NK cells (B) are shown. The average proportion of necrotic (7-AAD⁺annexinV⁺) T cells is shown (C). Open bars = memory CD4 T cells, closed bars = memory CD4⁺ T cells plus NK cells. N = 8 samples. A time-course analysis of apoptotic (7-AAD⁻annexin V⁺) T cells is shown (D). Open circles indicate memory CD4 T cells alone and filled squares indicate T cells plus NK cells.