Immunologic memory cells of bone marrow origin. Increased burst size of specific immunocyte precursors

Allogeneic hematopoietic transplantation and natural killer cell recognition of missing self

Although the optimal donor for allogeneic hematopoietic stem cell transplantation (HSCT) is a human leukocyte antigen-matched sibling, 75% of patients do not have a match, and alternatives are matched unrelated volunteers, unrelated umbilical cord blood units, and full-haplotype-mismatched family members. To cure leukemia, allogeneic HSCT relies on donor T cells in the allograft, which promote engraftment, eradicate malignant cells, and reconstitute immunity. Here, we focus on the open issues of rejection, graft-versus-host disease (GVHD), and infections and the benefits of natural killer (NK) cell alloreactivity and its underlying mechanisms. Donor-versus-recipient NK cell alloreactivity derives from a mismatch between inhibitory receptors for self-major histocompatibility complex (MHC) class I molecules on donor NK clones and the MHC class I ligands on recipient cells. These NK clones sense the missing expression of the self-MHC class I allele on the allogeneic targets and mediate alloreactions. HSCT from 'NK alloreactive' donors controls acute myeloid relapse without causing GVHD. We review the translation of NK cell recognition of missing self into the clinical practice of allogeneic hematopoietic transplantation and discuss how it has opened innovative perspectives in the cure of leukemia.

Cellular and humorial immune responses in mice. III. Acceleration of delayed hypersensitivity response by presensitization with suboptimal dose of antigen

Delayed hypersensitivity (DH) response in mice induced by subcutaneous (s.c.) injection of optimal dose of sheep red blood cells (SRBC) 10(8)) was accelerated by s.c. injection of the antigen of 10(3) or more doses, given 2 or more days earlier. The accelerated response appeared soon after the injection of optimal antigen dose, that is, 1 or 2 days earlier than the response of non-presensitized control. The acceleration was antigen specific. The accelerated response was generally accompanied by an acceleration and/or enhancement of humoral antibody response. Parallel to the acceleration of DH response, the proliferation of regional lymph node cells in the presensitized mice was induced immediately after the following injection of 10(8) SRBC, 1 day earlier than that of non-presensitized animals. These results suggest that presensitization of mice with the antigen induces DH-related memory cells which proliferate immediately after the following injection and function as effector cells for DH reactions, and that the development of DH-related memory cells occurs in close relation to that of helper thymus-derived (T) cells for antibody production.