Different Cells are Replaced at Different Rates

Different types of cells have different lifespans, e.g.:  we shed our skin cells about every 35 days red blood cells live about 120 days, platelets 6 days and white cells less than a day most of the adult skeleton is replaced about every 10 years the average age of a fat cell seems to be about 10 years a 25-year-old heart replaces about 1% of all its cardiomyocytes (heart muscle cells ) over the course of a year, while a 75-year-old heart replaces about half a percent ...

 The Immune System VS Viruses

The immune system consists of white blood cells that come in about 10 million different types. Each type has a protein lock on it called an "antibody," which corresponds to a key carried by a bacterium called an "antigen." If a key enters that lock, the white cell starts multiplying ferociously in order to produce an army of white cells to gobble up the key-carrying invader, be it a flu virus, a tuberculosis bacterium, or even the cells of a transplanted heart. But the body has a problem. It ...