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.
Stress and Back Pain. There is a strong connection between stress and back pain. Stress causes a release of stress hormones. Stress hormones increase the perception of pain. Stress hormones also cause the muscles to tighten up. The muscles may tense up so much they go into painful spasms. Muscle tension reduces blood flow to the tissues (reduced oxygen and nutrients to the tissues).