Current Controversies

The hypothesis that natural antibodies and the classical complement pathway are involved in all ischemia-reperfu-sion injuries might be oversimplified. The kidney was found to be protected in a model of kidney reperfusion injury using C3-, C5-, and C6-deficient animals, but not C4-deficient animals, implying that the classical pathway may not be the initiator of injury in all cases. In fact, another study indicated that complement might not be mediating renal ischemia-reperfusion injury at all as C3 inhibition with crry did not convey protection. These paradoxical results require investigation.

The classical, alternative, and lectin pathways also appear to communicate, much like the crossovers in the blood clotting system. The alternative pathway has been reported to be important in intestinal reperfusion injury using mice deficient in factor D [9]. It is possible that the classical pathway initiates injury but the alternative pathway is required for its amplification [10].

Lectin, the third pathway leading to complement activation, has been shown to attenuate myocardial reperfusion injury in rats given an MBL antibody post ischemia. These complement pathways may be species or organ specific, a phenomenon that might explain the different observations in the various animal studies.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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