What is the primary organ of the immune system among: thymus, appendix, spleen, lymph nodes, tonsil?
I would have to argue that the thymus is the most important among those listed. The two primary lymph organs are the bursal equivalent (bone marrow) and the thymus. The thymus is where T lymphocytes migrate to in order to mature. Without T cells, anindividual would be severely immunocompromised, since T cells provide cell-mediated immunity. In other words, when a T cell detects an infected cell, it either kills it or recruits other cells (e.g. macrophages) to kill it. Perhaps the best illustration of the importance of T lymphocytes is AIDS, which is characterized by a precipitous decrease in the number of helper T cells.
