Regulatory mechanism of delayed-type hypersensitivity in mice. III. In vitro analysis of memory T cells involved in augmentation of DTH responses.

Abstract

The memory of delayed-type hypersensitivity (DTH), manifested by the augmented responsiveness upon challenge with alum-absorbed ovalbumin (OA), was induced in mice primed 7 days, 21 days, or 90 days previously with 1 microgram of reduced and alkylated OA. The memory cells involved in the augmentation of DTH responses were analyzed in the in vitro induction system of T cells which mediate DTH against OA. Spleen cells from the primed mice generated DTH-effector T cells (DTH-Te) in a significantly accelerated fashion, compared with unprimed spleen cells, when cultured with OA. The accelerated generation of DTH-Te in vitro was induced antigen specifically and was dependent on a certain T cell population in the primed spleen. The T cell population was found in the spleen of primed mice for at least 3 months after priming, corresponding to the persistence of DTH-memory in vivo. Moreover, it was fractionated in the high-density layer by discontinuous bovine serum albumin gradient centrifugation. The high-density cell population decreased in density with increase in the time of culture and developed into DTH-Te, which were separated in the low-density layer on day 4 of culture. These results indicate that the T cells involved in the accelerated generation of DTH-Te in vitro are long-lived DTH-memory T cells, which are probably precursor cells, capable of differentiating into DTH-Te upon challenge with the antigen.