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.
The agency estimates that the odds of someone in the U.S. being struck by lightning in a given year are one in 500,000. Last year, 29 people were killed by lightning in the U.S., including two men who died in Texas. In 2009, Florida had the most fatalities of the 34 who were killed by lightning â five â followed by Texas and North Carolina, which each saw three fatalities.