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.
Muscle Knots in the Back That Are Big & Hard to Get Out. Knots in your back muscles can cause radiating pain that affects your entire body. Photo Credit Comstock Images/Comstock/Getty Images. Muscle knots in your back can be painful, especially if they are big and aren't going away. Some knots may cause mild discomfort, while others may affect your ability to sleep, work and move.