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.
Psychogenic Tight Back Muscles. Some of the most common reasons for ongoing muscle tightness in the back are conscious stress and subconscious repressed emotional issues. The mind and body work together in all aspects of our lives, including causing and curing all manner of injury, disease and pain.