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.
Causes of Back Pain. Lumbar Muscle Strain. Muscle strains are the most common cause of low back pain. Patients may or may not remember the initial event that triggered their muscle spasm, but the good news is that most episodes of back pain from muscle strains resolve completely within a few weeks.