We therefore next assessed the relative contribution of NK and T cells to total IFN-γ responses following exposure. Proportions of total T cells and NK-cell numbers within the PBMC population did not vary greatly between the time points (Supporting Information Table 1). Prior to challenge (day C−1), NK cells made up on average 14% of total IFN-γ+ lymphocytes responding to PfRBC, with T cells making up 71% (Fig. 1H). Despite the overall increase in responding cell numbers following challenge, relative contributions by NK cells and T cells to the IFN-γ+ response did not differ much immediately following exposure (17 and 68%, respectively, on day C+35). However,

thereafter the relative contribution of IFN-γ-producing T cells over NK cells BVD-523 in vitro increased slightly with time, with NK cells making up only 7% of IFN-γ+ lymphocytes 20 wk after challenge and T cells 83% (Fig. 1H), perhaps indicating a maturation of the immune response. Within the NK population, the relative proportion of responding CD56dim cells to responding Selleck RXDX-106 CD56bright cells remained roughly constant over time (data not shown). Notably, the proportions of responding T cells and NK cells appeared to be correlated within volunteers at all time points (Fig. 1I). Thus,

although the relative contribution of T cells over NK cells increases somewhat in relation to exposure, in vitro T-cell and NK-cell responses to PfRBC are closely linked within donors. Since both T cells and NK cells showed such parallel IFN-γ responses to stimulation with P. falciparum in vitro, we next investigated reciprocal interactions between these cell types using magnetic

bead depletion assays (representative FACS plots shown in Supporting Information Fig. 1B). Thalidomide In the absence of NK and NKT cells depleted with anti-CD56 beads, the capacity of T cells to respond to PfRBC was slightly reduced (Fig. 2A). However, depletion of CD3+ T and NKT cells completely abrogated the ability of remaining NK cells to produce IFN-γ against PfRBC (Fig. 2B). Notably, this effect must be largely due to T cells bearing an αβT cell receptor, since the depletion of γδT cells had little effect on NK-cell responses (data not shown). The requirement of T cells for NK-cell IFN-γ production has been described previously for NK responses to influenza virus 18 and HIV 19, but it remains unclear if this represents a ubiquitous requirement for NK-cell activation. Interestingly, NK cells still retained some responsiveness against PfRBC even in the absence of T cells, as evidenced by partial upregulation of the IL-2 receptor CD25 (Fig. 2C and D). Since IL-2 is produced by activated T cells post-exposure (Supporting Information Fig. 1g) and IL-2 signaling contributes to PfRBC-induced IFN-γ production by NK cells (Fig. 2E and F and 11), we investigated whether IL-2 might form the critical link between T-cell and NK-cell activation, as it does in the influenza model 18.