Understanding the immunological function of RBCs
Red blood cells (RBCs) are emerging as an important regulator of cell function and survival. A small, but important body of literature has now demonstrated that the inclusion of RBCs in culture with other cell types can initiate changes in what proteins are secreted from those cells. We have conducted further research into this area and have discovered that RBCs are capable of both binding and releasing cytokines in response to their local environment. This investigation demonstrated that:
Importantly, this study highlights that RBCs and their influence on the immune system can be altered. In disease, RBCs function differently and their control on immune cells is impaired. We have now also observed this by intentionally altering RBCs and their cytokine profile by exposing them to a lung cancer cell line (Figure 1). Following incubation with these cancer cells, these primed RBCs were loaded with a variety of pro-tumorigenic cytokines including bFGF, IL-8, and VEGF. Then, in the presence of these altered RBCs, T-cells were stimulated to proliferate to a greater degree (Figure 2), were no longer protected from stimulant-driven activation, and were driven to release a variety of cancer-related cytokines. In other experiments, RBCs incubated with a regenerative cell type (mesenchymal stem cells) produced a different, yet notable, cytokine profile indicating that this profile can be controlled.
Figure 1. Concentration of cytokines in red blood cell (RBC) lysates of naïve RBCs (unprimed) or red blood cells incubated with a secondary cell line (primed). These secondary cell lines included a lung cancer cell line (A549 cells), mesenchymal stem cells (MSCs), and a breast cancer cell line (MCF-7).
Since RBCs are considered to be inert, they have been advocated as optimal biological carriers of antigens or drugs for cancer immunotherapy. Loading red blood cells with tumour specific antigens has been demonstrated to stimulate an extended T-cell response in mice. Our results demonstrate that unlike previous studies, without the addition of antigens or drugs, RBCs can be modified to become more immunogenic or to selectively activate populations of immune cells (Figure 2). Primed RBCs could be valuable in the future as personalised immunotherapies. Sangui Bio is now in the process of exploring the effect of RBC based immunotherapeutics in animal models of disease.
Figure 2. Graphical representation of T-cell proliferation following treatment with naïve unprimed red blood cells (upRBC) or red blood cells primed with a lung cancer cell line (pRBC). Figure illustrates the effect of these treatments on the proliferation of (A) model T-cells (Jurkat cells), or (B) CD3+ T-cells, (C) CD4+ T-cells, (D) CD8+ T-cells isolated from PBMCs (peripheral blood mononuclear cells).
Karsten, E., Breen, E., McCracken, S. & Herbert, B. R. Red blood cells exposed to cancer cells in culture have altered cytokine profiles and immune function. Nature. Scientific Reports (2020).
Karsten, E. & Herbert, B. R. The emerging role of red blood cells in cytokine signalling and modulating immune cells. Blood Reviews. (2019).
Karsten E, Herbert B, Liddle A, Hill C. Therapeutic methods using erythrocytes. Priority date: 2015-12-22. Stage: National phase examination.