Specific heterologous enhancement of immune responses. 3. Partial characterization of supernatant material with enhancing activity.

Abstract

1.A soluble factor which enhanced the plaque-forming antibody response against sheep erythrocytes was found in tissue culture fluid of spleen cell cultures from mice injected with tetanus toxoid 1 to 2 months earlier to which 1 ng of toxoid was added on the 2nd day of a 5-day period of incubation. Such enhancement was demonstrated in normal spleen cell suspensions to which sheep erythrocytes were added at the beginning, and the supernatant on day 2. 2.In such cultures, enhancing factor was generated and appeared in the supernatant only after the addition of the specific antigen used for priming. Also, at certain concentrations, such supernatants produced inhibition of the response and hence contained a soluble inhibitory factor. 3.The enhancing factor is both non-dialyzable and heat stable (56°C, 30 min).