Great question that we haven’t explored yet. We refer only to phagocytosis in the paper because SCRs have similar effects on macrophage engulfment of E. coli and cancer cells (fig. attached) It is possible that SCRs increase efferocytosis, but we need to do more experiments.

These SCR(S3-S3-S3-S1) macrophages also have sustained expression and secretion of pro-inflammatory proteins like CXCL9, IL-15, IL-6, and CCL7.

We constructed the predicted SCR(S3-S3-S3-S1) and found it drove macrophages to a unique state combining efficient phagocytosis & high CD40 and CD80 expression.

We then used this model to overcome an inherent trade-off in our experimental dataset: the tested SCRs failed to generate a macrophage with a simultaneously pro-inflammatory and phagocytic profile — a potentially advantageous state for cancer therapy. Using the two-state model, we identified SCRs predicted to achieve this dual phenotype.

The 131 experimentally tested receptors represent a small fraction of possible SCRs. We wanted a simple model that captures the motif to phenotype relationship and predicts the polarization effects of untested SCRs. We found that a simple two-state model describes the data well. See Figure 5 for more details!

SCRs containing ‘YLxQ’ motifs (S2 and S3) enhanced phagocytosis of E. coli. We asked if this effect would generalize to enhance phagocytosis of cancer cells by CAR-macrophages. Both in vitro and in vivo, the answer was yes!

We recombined 9 different motifs to generate a wide spectrum of synthetic macrophage polarization states which differed in polarization markers like CD163, CD206, CD40, CD80, PDL1, and the capacity to phagocytose E. coli.

SCRs containing motifs from natural cytokine receptors were sufficient to polarize macrophages. For example, the 'YDKPH' motif (S1) from the IFNγ receptor mimicked IFNγ stimulation, while the 'YLRQ' motif (S3) from the IL-10 receptor mimicked IL-10 stimulation.

We used a synthetic cytokine receptor (SCR) platform to activate unique signaling programs in human primary macrophages in a cytokine-independent manner (see the platform’s debut in T cells biorxiv.org/content/10.1101/…). The signaling is programmed by varying motifs on the receptor’s intracellular domain.

🚨What if we could reliably program macrophage polarization state?🚨 biorxiv.org/content/10.64898… Macrophages are highly plastic immune cells that perform critical functions by polarizing into distinct cellular states. The polarization state of macrophages can substantially influences the progression of cancers, infections, and autoimmunity. (1/11)