Here we review the evidence for the interaction of the immune sys

Here we review the evidence for the interaction of the immune system with AML and results of recent vaccine LY294002 trials and outline developing immunotherapeutic strategies. There is abundant evidence that AML cells are susceptible targets of innate and adaptive immune responses.

AML cells express both major histocompatibility complex (MHC) classes I and class II, making them susceptible to T cell recognition and attack. They also express major immunogene complex (MIC)-A/B, one of the ligands for the activating NK cell receptor NKG2D. T cells and NK cells exert cytotoxicity through perforin-granzyme release, interaction of TNF-related apoptosis-inducing ligand (TRAIL) with death receptors on the target causing apoptosis, and indirectly through cytokine production of inflammatory cytokines tumour necrosis factor (TNF) and interferon (IFN) [4–6]. The most NVP-AUY922 compelling data for the susceptibility of AML to immune attack comes from experience with allogeneic SCT, where both T cells and NK cells are implicated in the GVL effect [3]. Humanized severe combined immunodeficiency (SCID) mouse models demonstrate that T cell clones derived from patients after allogeneic SCT can prevent and control the emergence of human leukaemia in vivo[7,8]. In vitro, a number of studies show that AML cells are targeted by donor T cells after SCT and at least one minor

histocompatibility antigen (mHAg) on AML cells has been characterized [9]. Allogeneic NK cells are cytotoxic to AML targets that do not express cognate human leucocyte antigen (HLA) molecules for the killer immunoglobulin-like

receptor (KIR) on the donor’s NK cell, protecting allorecipients from relapse [10]. Other allogeneic interactions between NK cells and targets that do not follow the ‘missing self’ rule also occur in HLA-identical SCT. Notably, donors possessing KIR groups of the B haplotype confer protection against relapse in both HLA matched unrelated [11] and related SCT [12]. Transplant data suggests that NK mediated GVL is very specific for myeloid leukaemias. Cytotoxic interactions also occur between autologous lymphocytes and AML cells. It has been known for many years that fresh autologous leukaemic blasts are lysed Edoxaban by cytokine-activated NK cells [13,14]. AML expression of NK ligands, including MHC class I molecules and CD44, determines their susceptibility to NK attack. A high expression of HLA-G, HLA-Bw4 and HLA-C protects AML cells from NK lysis and is associated with poorer outcome after chemotherapy [15,16]. T cells recognizing autologous AML cells have been generated in vitro in prolonged culture where the T cells are restimulated with AML antigen-presenting cells [17,18] and T cells specific for several antigens expressed on AML cells (WT1, PR1, PRAME) are often detected in patients with AML compared with infrequent low levels of expression seen in healthy individuals [19,20].

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