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.
1 What causes knots in your back. 2  How trigger points cause knots - and what they are. 3  How to relieve your knots naturally with steps you can start taking right away. 4  Why your back muscles are complaining.  How muscles in your neck can cause knots in your back.