Studies on immune responses in afferent and efferent lymph of lymph nodes draining the tissues have contributed to the concept that primary immune responses are generated in the lymph nodes with a delay before antigen-specific effector cells arrive at the affected tissue.
Lightning strikes the ground approximately 25 million times each year in the U.S. According to the NWS, the chance of an individual in the U.S. being killed or injured during a given year is one in 240,000. Assuming an average life-span of 80 years, a person's odds over their lifetime becomes one in 3000.
What happens when lightning hits? You have to be quite unlucky to be killed by lightning â only about 10% of the people hit each year die â but being struck by lightning is a far from pleasant experience as Roy Sullivan can attest. A park ranger, he was struck seven times between 1942 and 1977 and suffered a range of disabling injuries.