When our body gets sick, we send out special soldiers called white blood cells to fight off the bad guys. One type of white blood cell is called a B cell, and its job is to make special weapons called antibodies to fight off germs and viruses.
But when things get really serious, like during a big infection, our body needs to call in the big guns. This is when the B cells turn into immunoblasts. Immunoblasts are like really strong soldiers who can make a ton of antibodies to fight off the bad guys. They multiply really quickly so that we have enough soldiers to win the battle against sickness.
Once the immunoblasts have done their job and won the battle, they turn back into regular B cells again. But they keep a memory of how to fight that same germ or virus, so that if it ever comes back, they can quickly become immunoblasts again and fight it off just as fast.