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.
Back strain is the most common cause of back pain, especially lower back pain. Muscle strain is often caused by overuse of a muscle or overloading a muscle. When a muscle is stressed beyond its limits, injury occurs. With injury comes inflammation, which is part of the healing process.