Bone marrow contains tissue that produces lymphocytes. B-lymphocytes (B-cells) mature in the bone marrow. T-lymphocytes (T-cells) mature in the thymus gland. Other blood cells such as monocytes and leukocytes are produced in the bone marrow.
However, Soma and anxiety is not one of these situations. Since the anti-anxiety effects of Soma are not very strong, you would need to take unsafe amounts to treat your anxiety. A good doctor would not prescribe Soma for your anxiety and would suggest other alternatives.
Whatever the answer to your question, snris work on both serotonin and norepinephrine receptors, so if the snri relieved your anxiety it's very unlikely norepinephrine is causing your anxiety -- by taking the snri you just increased the functioning of it and you reduced your anxiety.