C3a concentrations are reportedly elevated during inflammatory diseases7, recombinant C3a reportedly induces hypertension and delayed neutrophilia in rats over 24 h8, while sustained activation of C3aR vs knockouts support a role in allergies9, asthma10, arthritis11, sepsis12, lupus13, diabetes14, ischemia-reperfusion injury15, obesity and metabolic dysfunction16. The gene discussed is C3; the disease is obesity due to melanocortin 4 receptor deficiency.