Abstract
Supernates derived from in vitro generated T[thymus-derived]-helper cells were analyzed for their capacity fo substitute for T-cell carrier reactivity. T-helper cell supernates stimulate a carrier-specific and nonspecific anti-DNP-PFC [dinitrophenol plaque-forming cell] response to DNP-carrier conjugates in cultures of hapten-primed spleen cells. The carrier-specific and nonspecific activity can be distinguished by dosage optimum, antigen requirements, binding specificity for carrier and in the requirement for additional splenic adherent accessory cell involvement. The active factors produced in this system are heat labile and sensitive to trypsin and periodate. They are removed by absorption with alloantisera directed toward the strain from which the supernate was derived but not by a variety of anti-immunoglobulin sera.