Role of mediators of cellular hypersensitivity in the stimulation of the antibody formation to unrelated antigen

The effect of a concurrent delayed hypersensitivity reaction on the antibody response to sheep red cells was assessed by a plaque assay. Guinea pigs with delayed hypersensitivity to tuberculin purified protein derivative (PPD) or egg albumin showed an increased antibody response to sheep red cells when the cells were injected intravenously at the same time as PPD or egg albumin. This effect was transferred to normal guinea pigs by serum from guinea pigs with delayed hypersensitivity to PPD or egg albumin taken 24 hr after injecting the corresponding antigen. Supernatants containing migratory inhibitory factor were prepared by incubating lymphocytes from sensitized rabbits with antigen. These supernatants were injected with sheep red cells and gave rise to an enhanced plaque response. Similar results were obtained with supernatants from normal rabbit thymus cells. The role of mediators of delayed hypersensitivity in enhancing antibody formation and in T cell/B cell cooperation is discussed.