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.
Additional Lightning Information. An average of 49 people are killed each year by lightning, based on data from 1985 to 2014. July is the peak month for lightning fatalities, based on data from 2006 to 2013. Not surprisingly, June is the second highest month and August comes in third place.