Complex sentence: An antigen in the mushroom can trigger the immune system to attack red blood cells with potentially fatal complications, including acute renal failure, shock, acute respiratory failure, and disseminated intravascular coagulation.
Split into simpler sentences: An antigen in the mushroom triggers the immune system to attack red blood cells. Serious and potentially fatal complications include acute renal failure, shock, acute respiratory failure, and disseminated intravascular coagulation.