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.
The anxiety can be somaticized into tense muscles anywhere in the body. If you add to that extra stress, it can just compound the problem. Getting in touch with your body and learning how to let go of stress/tension in it through bodywork and relaxation is the starting point.