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 earth experiences about 44,000 thunderstorms every day, with approximately 1,800 storms in action at any given moment. The most active area in the world is Java, an island of Indonesia, with an average of 223 storm days per year. Florida is known as the lightning capital of the United States, with storms occurring approximately 100 days out of the year, compared to California's low of only 5.