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.
Low Back Pain: Causes. Back pain can be caused by a wide variety of factors. These include structural problems of the back, inflammation, muscle and soft tissue injury, secondary response to other diseases or conditions, imbalances in body mechanics, and psychological/social factors, among others.