phenotype affects entity mammalian phenotype immune system phenotype MPheno.ontology the observable morphological and physiological characteristics of the mammalian system that protects the body from foreign substances, cells, and tissues by producing the immune response and that includes especially the thymus, spleen, lymphoid tissue, lymphocytes including the B cells and T cells, and antibodies that are manifested through development and lifespan MP:0005387 immune system immune system phenotype