IMMUNOLOGY2026™ Conference Recordings For Attendees-Complement and immunosuppressive tumour microenvironments

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Video Summary

Dr. Alcina from Oxford discussed how the complement receptor C5AR1 helps tumors survive in immunosuppressive microenvironments and how blocking it may improve treatment. She showed that tumors with low TILs usually have worse outcomes and that complement proteins are often produced locally in tumors, where high expression can correlate with poor prognosis. In colorectal cancer models, radiation increased C5AR1 in tumor cells, and inhibiting C5AR1 with PMX205 boosted radiation-induced apoptosis, delayed tumor growth, and improved survival, even in mice lacking T cells. Importantly, this combination did not increase damage in normal intestine and may even reduce toxicity. She also found that severe hypoxia strongly induces C5AR1, partly through ER stress and intracellular receptor pools. A more cell-permeable inhibitor, avacopan, was especially effective in hypoxic tumor spheroids. Overall, C5AR1 may be a promising target to enhance radiotherapy response while limiting normal tissue injury.

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Date April 18, 2026 9:45 AM - 11:15 AM

Room 104C

Session Complement - Key Modulator of Tissue Autoimmunity and Inflammation, Sponsored by the Intl. Complement Soc. (ICS)

Speaker Monica Olcina

Track Basic Autoimmunity (BA)

Year 2026

Keywords

C5AR1

radiotherapy

colorectal cancer

tumor microenvironment

hypoxia

complement receptor

April 18, 2026 9:45 AM - 11:15 AM

104C

Complement - Key Modulator of Tissue Autoimmunity and Inflammation, Sponsored by the Intl. Complement Soc. (ICS)

Monica Olcina

Basic Autoimmunity (BA)

2026