The CMY colours (commonly mistaken for Blue, Red and Yellow) are the answer when printing as mixing any two will form one of the darker RGB colours. The mix of all three CMY colours creates Black, although in practice this is very muddy.
White blood cells, like all blood cells are created in the bone marrow from certain stem cells. However, some lymphocytes are created but undeveloped or immature.
Known as the body's first line of defense, your immune system and lymphatic system help protect you from bacteria, viruses and fungi that cause disease. Your lymphatic system produces and carries white blood cells containing antibodies that fight off infection.