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.
Heat Lightning: Lightning from a thunderstorm that is too far away to be heard. Lightning Facts: - Lightning causes an average of 80 deaths and 300 injuries each year. - The energy from one lightning flash could light a 100 watt light bulb for more than 3 months.