Naïve Rat NK Cells Control the Onset of T Cell Response
Figure 6
NK cells control the response of naïve but not of activated T cells. A:
To confirm that NK cells rather control the T cell response than suppress, 2×105 splenocytes were depleted of NK cells and response to 2×103 L23 was assessed in the absence or presence of 2×104 NK cells incubated in transwells. Depletion of NK cells increased the proliferative response of splenocytes significantly which could be reversed by contact independent return of NK cells in transwells (TW). B: The control of proliferation of T cells by NK cells in bulk splenocytes is combined with a control of cytokine response e.g. IFN-γ as one of the important inflammatory cytokines. C: For evaluation of regulatory function of NK cells at different stages of immune response, 2×105 splenocytes from naïve and 14 days L23-immunised LEW.BH-NKC rats were used as responder cells. Splenocytes were incubated as bulk or NK depleted cells with 2×103 L23 cells. Thus, for naïve cells this was the initial stimulation, for immunised splenocytes it was a specific re-stimulation. The naïve spleen cells responded to L23 stimulation with increased proliferation after NK-depletion whereas using immunised splenocytes a decrease in proliferation was detected. D: Assessment of IFN-γ revealed a strong increase in cytokine secretion in naïve splenocytes depleted of NK cells but a decrease in NK-depleted immunised splenocytes. E: To evaluate if NK cells derived from immunised rats lost the regulative capacity, 2×105 spleen cells from naïve and immunised rats were depleted of NK cells, stimulated with 2×103 L23 cells and cross-incubated with 2×104 purified naive NK cells or derived from immunised rats. Stimulation of NK-depleted splenocytes with L23 cells induced comparable proliferation in spleen cells derived from immunised and rats. While the proliferation of naive splenocytes could be influenced by both NK cells isolated from naïve and immunised rats, no control of immunised splenocytes was detectable. In contrast, both type of NK cells increased the proliferation as could be observed in (C). Results are shown as representative scattergram of FACS analysis or as graphs summarize results of at least three independent experiments as mean ± standard deviation. **p≤0.01; *p≤0.05; n.s. = not significant.