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.
It heats the air it zips through to five times the surface temperature of the sun. Still, around 90 percent of lightning-strike victims survive. Over the past three decades, lightning has killed an average of 51 people per year in the U.S. but left more than 500 injured and alive.