Intrathymic cortisone-resistant memory cells (46.11)

Abstract

Abstract It is known that central memory cells CD8+ are found in immunocompetent lymphoid organs, such as spleen and lymph nodes. Previously, we described the approach allowing to see and estimate selective proliferation of memory cells in MLR with heat-silenced (45 degrees, 1 h) allogeneic stimulator splenocytes. We immunized C57BL/6 (H-2b) mice intraperitoneally with mastocytoma P815 cells (H-2d). Two months later, we tested the proliferation of thymocytes in the MLR with heat-silenced syngeneic C57BL/6 (H-2b), allogeneic B10.D2 (R101) (KdIdDb) and third-party FVB (H-2q) splenocytes. Thymocytes of intact mice did not respond in MLR at all. Thymocytes of immune mice displayed small, but significant MLR responses to heat-silenced allogeneic splenocytes, but not syngeneic or third-party splenocytes. To test the hypothesis that thymic memory cells are cortisone-resistant, we treated immune mice with hydrocortisone. Injection of high dose of hydrocortisone (2,5 mg) 2 days before isolation of responder thymocytes resulted in highly elevated MLR responses. This response was antigen-specific because “immune” thymocytes responded only on heat-silenced R101, but not syngeneic or third-party splenocytes. As expected, in proliferating cultures, the ratio of CD4/CD8 was less than 1 due to proliferation of memory CD8+ cells, responding on H-2Kd MHC class I molecule represented on R101 thymocytes. Thus, we have found that the thymus contained memory-like T cells, which are cortisone resistant.