The Challenges of Precision Medicine and New Advances in Molecular Diagnostic Testing in Hematolymphoid Malignancies: Impact on the VHA.

The Hematopathology Molecular Genetics subcommittee presents recommendations for molecular diagnostic testing in acute myeloid leukemia, myeloproliferative neoplasms, myelodysplastic syndrome, and lymphomas and for the development of an interfacility consultation service.

Innate immunity alone is not sufficient for chronic rejection but predisposes healed allografts to T cell-mediated pathology.

Background: Acute allograft rejection is dependent on adaptive immunity, but it is unclear whether the same is true for chronic rejection. Here we asked whether innate immunity alone is sufficient for causing chronic rejection of mouse cardiac allografts.

Methods: We transplanted primarily vascularized cardiac grafts to recombinase activating gene-knockout (RAG(-/-)) mice that lack T and B cells but have an intact innate immune system.

Lymphoid neogenesis in murine cardiac allografts undergoing chronic rejection.

Lymphoid neogenesis is the process by which ectopic lymphoid accumulations that resemble lymph nodes arise in nonlymphoid tissues. Such lymphoid accumulations, known as tertiary lymphoid organs (TLO), are observed in chronic autoimmunity and they propagate immune pathology by setting up local antigen presenting sites. Whether lymphoid neogenesis occurs in transplanted organs and contributes to rejection is not well understood.

Direct antigen presentation by a xenograft induces immunity independently of secondary lymphoid organs.

The location of immune activation is controversial during acute allograft rejection and unknown in xenotransplantation. To determine where immune activation to a xenograft occurs, we examined whether splenectomized alymphoplastic mice that possess no secondary lymphoid organs can reject porcine skin xenografts. Our results show that these mice rejected their xenografts, in a T cell-dependent fashion, at the same tempo as wild-type recipients, demonstrating that xenograft rejection is not critically dependent on secondary lymphoid organs.

The allograft defines the type of rejection (acute versus chronic) in the face of an established effector immune response.

Transplanted organs fail due to either acute or chronic rejection. The prevailing view is that the nature or magnitude of the recipient's immune response to donor Ags determines the type of rejection. In variance with this view, we show in this study that the status of the graft itself plays a dominant role in defining the type of rejection even in the face of an established alloimmune response.

Recall and propagation of allospecific memory T cells independent of secondary lymphoid organs.

The allospecifc T cell population responding to a transplanted organ consists of both naive and memory lymphocytes. Although it is established that naive T cells are activated by antigen within the organized structures of secondary lymphoid organs (the spleen, lymph nodes, and mucosal lymphoid tissues), it is not clear whether memory T cell activation and propagation depend on homing to these organs. To answer this question, we investigated whether allospecific naive or memory T cells can mediate acute cardiac allograft rejection in mutant mice that lack all of their secondary lymphoid tissues.