Active and Passive Immunity. Naturally acquired active immunity occurs when the person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the primary immune response. Artificially acquired active immunity can be induced by a vaccine, a substance that contains the antigen.
Lower back tightness can cause muscle twitching, pain and reduced range of motion. Lower back muscle tightness is the cause of a muscle spasm. This can be brought on by a strain, overuse or muscle weakness, according to BetterMedicine.com.
Other people may experience low back pain as a result of bowel problems such as constipation, diarrhea or irritable bowel syndrome. This is because the nerves that go to and from the bowel originate in the lumbar spine. These same nerves also go to the muscles and ligaments that stabilize the low back.