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.
Stiffness felt throughout your back muscles comes from increased tension in your muscle tissue. The stiffness and back pain may occur in your upper back -- the thoracic and cervical regions -- or your lower back -- the lumbar region. Causes of increased muscle tension include trauma, overuse and poor posture.