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.
Acute low back pain is most often caused by a sudden injury to the muscles and ligaments supporting the back. The pain may be caused by muscle spasms or a strain or tear in the muscles and ligaments. Causes of sudden low back pain include: Compression fractures to the spine from osteoporosis.