Cellular cooperation in the expression of murine delayed-type hypersensitivity (DTH): dual roles of accessory cells.

A recently described murine local passive transfer (LPT) system was modified to investigate accessory cell function in the expression of in vivo delayed-type hypersensitivity (DTH). An enriched antigen-presenting accessory cell population was prepared by overnight culturing and antigen pulsing. These cells, when cotransferred locally with enriched populations of immune DTH effector T lymphocytes, induced antigen-specific DTH responses. A consistently positive relationship between DTH expression and quantity of pulsed cells transferred was demonstrated. The further addition of fresh accessory cells to the transfer mixture provided 'augmentation' of DTH responses. In contrast to antigen presentation, 'augmentation' appeared restricted to an optimal range of augmenting cell: T cell ratios. That antigen presentation and augmentation were separate accessory cell functions was further supported by differential selection during overnight culture and differential sensitivity to paraformaldehyde (pCHO) exposure. The demonstration of multiple accessory cell functions indicates considerable promise for this system in the investigation of in vivo immune expression.