Currents of Protection: Coagulation, Complement, and Neutrophils is a work of creative nonfiction that journeys across science, history, and the humanities to understand the deep entanglement of blood and defense. At its heart is the "triangle" of coagulation, complement, and neutrophils. The three intertwined systems that seal wounds, fight microbes, and sacrifice themselves for the survival of the body. Yet the book insists that this triangle cannot be understood within the laboratory alone. Its story stretches across species, across time, and across the meanings humans have attached to blood.

The opening chapters introduce the triangle of blood and defense, then expand outward into comparative evolution, showing how clotting and immunity appear not only in humans but also in fish, reptiles, birds, and mammals, and even how extremophiles adapt their protective currents to hostile environments. From there, the narrative shifts from biology to history: the blood sciences across time, tracing how ancient physicians, alchemists, and natural philosophers imagined blood's power, and how folk knowledge. The book also reaches deep into prehistory, reconstructing the origins of blood and defense in deep time, then following their arc through human development, from the fetus in the womb to the aged body where protective systems falter. It confronts the darker side of protection, where coagulation, complement, and neutrophils (meant to preserve life) turn against the host, driving autoimmunity, thrombosis, and inflammatory storms. This book contains various chapters on: intervention, where medicine bends these currents through anticoagulants, immunotherapies, and transfusion sciences; semiotics, where symbols, rituals, and metaphors shape cultural understanding; and treconstitution, where gene editing, synthetic biology, and future medicine imagine new forms of protection altogether.

Weaving together molecular biology with anthropology and medical history, Currents of Protection invites readers to see blood not only as fluid but as narrative, as system, and as symbol. It is at once a primer on the science of clotting and immunity, a comparative study of defense across the tree of life, and a meditation on what it means to protect and be protected.

For scientists, it offers clarity; for historians, context; for physicians, reflection; for general readers, a story that runs as deeply as blood itself.

Brian Pollo is an MD-PhD candidate, educator, and writer whose work spans biochemistry, ethnomedicine, and the history of science. They study how complement, coagulation, and innate immunity adapt in extreme environments, while also tracing the cultural and symbolic roles of blood in human storytelling. Their writing blends scientific rigor with narrative inquiry, reflecting a commitment to both biomedical innovation and the preservation of ancestral knowledge.