Table 1.

Glossary of terms.

Term	Definition/Function
B-cells	Upon primary infection or immunization, a small population of antigen-specific B-cells becomes activated and expands after acquiring T-cell help. Some of these expanded clones then differentiate into memory B-cells.
CD8+ cytotoxic T-cells (CTLs)	T-cell exposure to antigens expressed on cancer cells and co-stimulatory signals leads to the development of effector function and T-cell clonal expansion. T-cell receptors on CD8+ T-cells bind to antigen, which is held in the major histocompatibility complex (MHC) complex on the surface of antigen-presenting cells, such as DCs. This then triggers initial activation of the T-cells.
Dendritic cells (DCs)	DCs efficiently process and present antigens to T-cells responsible for the initiation of immune responses.
Immune checkpoint: cytotoxic T lymphocyte antigen 4 (CTLA-4)	CTLA-4 is a cell-surface receptor, homologous to CD28, binding to ligands CD80/CD86 on antigen-presenting cells such as DCs. The binding of CTLA-4 to CD80 and CD86 is considerably stronger than the affinity of CD28, but unlike CD28 which activates T cells, CTLA4 delivers an inhibitory signal to T-cell activation. Thus, in cancer, CTLA-4 has undesirable effects that may prevent T cells from mounting a sufficient immune response.
Immune checkpoint: Programmed death 1 (PD1)	PD1 is one of the crucial immune checkpoint signals and is mainly expressed on mature CTLs. Interactions of PD1 with its ligand–PD ligand 1 (PDL1) reduce antigen-specific T-cell activation.
Leukemia-associated antigens (LAAs)	LAAs are immunogenic antigens which are able to induce specific T-cell responses and are target structures relevant for immunological targeting of leukemic cells.
Natural killer (NK) cells	NK cells lack T-cell markers but express CD56. Unlike T-cells, NK cells are not restricted to MHC-I/II molecules and can exert natural cytotoxicity against cancer cells based on signals from activating and inhibitory cell-surface receptors. CD56dim cells are more differentiated and cytolytic. A subset of NK cells with CD57 expression further differentiates the functionally diverse CD56dim subset and are considered ‘memory-like’ NK cells with higher cytotoxicity.
Natural killer cell receptors	NK cell receptors are classified into two types—‘inhibitory’ and ‘activating’. Major activating receptors involved in target leukemic cell killing are KIR2DS, natural cytotoxic receptors (NCRs)—NKp30, NKp46, and NKp80 and NKG2D. Tolerance of NK cells to normal cells is attained through their expression of MHC-I-binding inhibitory receptors including killer cell immunoglobulin-like receptor (KIR)2DL and natural killer group 2A (NKG2A).
Plasmacytoid dendritic cells (pDCs)	pDCs are a unique DC subset and produce large amounts of interferon (IFN)-α. Activated pDCs have strong antigen-presenting capacity, which plays an important role in NK cell recruitment and T-cell activation.