Growth and Maturation of Single Clones of Normal Murine T and B Lymphocytes In Vitro

At one stage of their differentiation, lymphocytes are resting cells—they do not divide, do not synthesize DNA, and show no immune effector functions. Most T and B cells responsive to antigen are believed to be in such a resting state. Antigens and mitogens stimulate these resting cells to DNA synthesis and division and to the development of effector functions. The differentiated effector function of B cells is the secretion of immunoglobulins (Ig), whereas those of T cells involve the help or suppression of B-cell growth and maturation and the killing of target cells. The magnitude of a response of lymphocytes to stimulation is determined by (1) the number of responding cells, (2) the number of divisions that the responding cells undergo, and (3) the efficiency of maturation of the stimulated cells to effector functions. When exposed to lymphocytes at immunogenic doses, antigens will activate only a restricted number of antigen-specific...